Comments On: Baboon Mothers and Infants

Baboon Mothers and Infants by Jeanne Altman excerpts part 1
ONE OF THE FIRST things that strikes anyone who follows a group of baboons across the African savannahs is how much time and energy they spend just making a living: feeding, walking, avoiding predation. The surprise is particularly great for those who have watched captive monkeys, or even have seen films of wild primates, for these films are inevitably constructed from the 10 percent (or less) of the daytime that the animals spend socializing, not the 65 to 70 percent of the time they spend walking and feeding. One can easily overlook these activities of maintenance or production. In captivity such activities occupy only 10 to 20 percent of the day even in large enclosures or small islands with provisioning and typically involve nothing more than picking prepared food pellets out of a hopper. In the baboons' natural habitat, however, it is impossible to ignore these activities when animals walk several kilometers a day in the hot sun, when they laboriously dig bulbs or grass corms from the ground for much of the day, and when their rest periods seem necessary for recovery from fatigue, rather than just a response to boredom. Thus, in our studies of yellow baboons, Papio cynocephalus, in Amboseli National Park, Kenya, my colleagues and I have been led--no, virtually forced--by our animals to consider their lives as an integrated whole and not as composed of in dependent social and nonsocial pieces. In all likelihood, the fact that they spend three-quarters of their day making a living in itself affects their other activities; and not just in how much time they have avail able for those other activities, which is immediately obvious, but in much more complex ways as well. It is some of these complexities that I shall explore in the following analyses.
Two particularly crucial life stages for any primate are those of motherhood and infancy. Most field studies of wild primates have included qualitative descriptions of mothers and infants, and some provide quantitative results for a few behaviors or for a few typical individuals. In addition, quantitative studies of captive nonhuman primate mothers and infants have been conducted on a variety of species and have included a wide range of social settings, from isolation studies to those conducted with small groups of mixed ages and both sexes. Most of these studies have focused on infants rather than mothers and have emphasized predictions of adult behavior and effects of mother-infant separation as part of an attempt to provide a monkey model for human mother-infant separation. They have included both "purely" observational and more experimental investigations. However, with but rare exceptions, systematic quantitative studies of mothers and infants in the complexity of natural settings have been absent from research on both human and nonhuman primates, and studies of environmental influences have been limited primarily to a few elements in the social environment.
This study is an attempt to assess the nature and extent of external influences on baboon mothers and their young infants. My general goal was to identify and measure factors affecting survival and behavior during motherhood and infancy, and to identify likely ontogenetic origins of differences in adult behavior and life history patterns. Toward this end I collected systematic ecological, demographic, and behavioral data on all baboon mothers in a group in Amboseli National Park, Kenya, for which long-term life history data were available on individual members.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 2
The project had several specific goals generated by the overall aims. First, I sought an understanding of the demography of motherhood and infancy. Are these high-risk periods for baboons, as they are for other animals? To answer this, I turned to the demographic data that my colleagues and I collected from 1971 through 1978. Such information accumulates slowly, and David Post, Jane Scott, Sue Ann McCuskey, Francis Saigilo, Jeffrey Walters, David Stein, and especially Stuart Altmann and Glenn Hausfater have all contributed to its collection. From these data I was also able to examine the effects of maternal age, dominance rank, and infant gender on mortality and the effects of maternal dominance rank on infant gender.
Next, I sought a quantitative description of the nonsocial milieu or ecology as it affected mothers and infants and a test of the extent to which this ecology limits infant survival and the timing of births and of weaning. Further, I asked whether mothers' time budgets were affected by their dominance rank and, if so, whether these effects were reflected in differential survival or in the time or attention available for infant care.
Another set of related questions involved the social milieu. In what ways does a female's social life change when she gives birth? Which changes are beneficial and which harmful? What are the nature and sources of individual differences in social milieu among mothers? In the literature of behavioral biology, much attention has been directed to the relationship between male dominance rank and reproductive success yet for a number of primates female dominance ranks have been shown to be more stable both within and between generations. Few field studies identify either the onto genetic origins of female dominance relationships or their potential evolutionary consequences. Can we identify the origins of dominance rank "inheritance" in these early social interactions? Who are the individuals who constitute the social world of mothers and infants? Are they members of particular age classes? Are they particular individuals? Are the individual preferences in choice of associates observed in sexual consortships also manifested at this time?
With an understanding of the ecological and social milieu and the demographic (e.g., age, parity) and sociological (e.g., dominance rank) characteristics of the mothers, I could determine not only whether these variables affect each other, affect mothers directly, and affect infant mortality, but also whether they affect maternal care, the mother infant relationship, and infant development.
Recently, models of the evolution of parent-offspring relations, have been developed to explain phenomena such as weaning conflict and to make predictions about aspects of parental care that evolve through natural selection. Models of the evolution of behavior are economic models; their major parameters include costs and benefits of behavior, usually measured in the "currency" of fitness, of survival and reproduction, and of relative representation of genes in the next generation. Assuming a degree of heritability of the behavior in question, one is then concerned with attempts to estimate these costs and benefits. Does the behavior appear to be selectively advantageous or disadvantageous? The answer, of course, will not tell us whether any behavior evolved through natural selection. However, given certain assumptions about the population, the mating system, and the heritability of the traits involved, the answer will suggest whether the behavior could have spread at least partially through natural selection.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 3
This book is about motherhood and infancy more than about "mothers" and "infants": motherhood and infancy are only two stages, albeit particularly important ones, in the life histories of individuals whose lives extend before and, one hopes, after these periods. Females enter motherhood with their pasts and they and their infants carry into their futures the marks of their experiences during the life stage they so intimately share. Even during this period females' lives remain more complex and multifaceted than the label "mother" or "motherhood" implies. It is the pasts and the futures and the concurrent facets of their lives that I shall examine and relate to the experiences of motherhood and infancy.
In all aspects of the present study, one fact recurs: baboon mothers, like most primate mothers, including humans, are dual-career mothers in a complex ecological and social setting. They do not take care of their infants while isolated in small houses or cages as the rest of baboon life goes on. They are an integral part of that life and must continue to function within it. The baboon world affects them, and they it, throughout their lifetime. Determining the consequences of limited available time and the effects of maternity, social milieu, and physical environment on individuals' time budgets constitutes a major thrust of this investigation.
For short-lived animals the life history approach to the study of behavior is common. In studies of primates, including humans, it is much rarer, partially because life histories are so long and each stage is sufficiently complex to keep researchers themselves occupied for whole lifetimes. The work that follows is one, necessarily incomplete, attempt to combine a life history approach with the quantitative study of primate behavior in the field.
The general problems that face most human and nonhuman primate mothers are in many ways similar. High rates of infant mortality and appreciable maternal risk have probably been characteristic of most human and other primate populations. Rates of birth and death will determine the relative ages of siblings, affect the size of age cohorts and other aspects of the social group in which mothers and infants find themselves. Likewise, ecological and social factors that affect mortality will be important aspects of motherhood and infancy.
The complex ways in which members of society provide support and also transmit existing social structure to infants are important for any primate mother. If we can begin to understand the origins of normal differences in maternal behavior, we shall be better able to predict the consequences of changes in these factors.
By examining the problems of motherhood and infancy in detail for one primate species we may learn questions to ask, parameters that should be measured, and possible strategies for studying complex ecological and social relationships in related species. Just as the study of another human culture sometimes provides a different perspective, new insights, occasionally new answers, and more often new questions, I hope that this attempt to deal with the complexity of experience in a study of baboon motherhood and infancy will strike some familiar chords or stimulate some new ideas in those whose main interest is in another species, perhaps even our own.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 4
BABOONS (Papio spp.) are large, group-living, Old World monkeys, full-grown males weighing about 23 kilograms, females 11 to 12 kilograms. There are several species of baboons, exhibiting various social structures and occupying a wide variety of African habitats. Baboons are among the most terrestrial of the monkeys, a feature that makes them more observable than most other primates and has led also to attempts to regard them as models for hominid evolution.
Despite the widespread use of baboons in medical research, few behavioral studies have been conducted on members of the genus in captivity. Major early exceptions were Hans Kummer's study of hamadryas baboon (Papio hamadryas) social organization in the Basel Zoo and Thelma Rowell's investigations of captive olive baboons (P. anubis), particularly of female social relations and infant development. Terrence Anthoney (1968) and Gilbert Boese (1975) studied the Brookfield, Illinois, colony of guinea baboons (P. papio), and more recently Anthony Coelho, Claud Bramblett and colleagues have begun long-term studies of several Papio species and hybrids at the Southwest Foundation for Research and Education. In contrast, rhesus monkeys (Macaca mulatta), other macaque species, and squirrel monkeys (Saimiri sciureus) have been major subjects of behavioral investigations for many years, especially at the Japanese Primate Centre and in laboratories such as those of Bernstein, Harlow, Hinde, Jensen, Kaufman, Mason, Mitchell, Ploog, Rosenblum, and Sackett, where research has often focused on infant development and the ontogeny of behavior.
Field studies of the various Papio species have had a very different history. At the turn of the century Eugene Marais lived for several years with chacma baboons (P. ursinus) in South Africa. Only recently, many years after his death, was his unfinished manuscript found and published, providing a sometimes strange but intriguing view of baboon life. In the 1950s field studies began in earnest; research on chacma baboons by Bolwig and by Hall and on olive baboons by DeVore were the first of what have become a growing variety of investigations of the several baboon species. Kummer's field study of social organization of hamadryas baboons, Stolz and Saayman's of the behavior of chacma baboons, Thelma Rowell's field research on olive baboons, and the Altmanns' study of the ecology of yellow baboons all followed shortly after, in the 1960s. Most of these studies were general investigations producing qualitative or quantitative descriptions of aspects of ecology or behavior. An annotated bibliography of the early field studies has been published by Baldwin and Teleki (1972). The less closely related gelada baboon, Theropithecus gelada, has been the subject of research for a number of years in the Semien mountains of Ethiopia, particularly by Crook, the Dunbars, Kawai, Osawa, and Mori.
The 1970s have seen two major changes in the conduct of baboon field studies. First, research is more focused and problem oriented and is often concerned with hypothesis testing: following up on questions raised by the more general studies, by theoretical considerations (e.g., foraging and kin selection theory), or by laboratory investigations of other species. This change was foreshadowed in the second wave of studies in the 1960s and is partially paralleled by changes in field studies of other species. Second, long-term studies were initiated at several sites. These two changes, combined, are beginning to result in longitudinal, life history studies of known individuals and in-depth investigations that have involved researchers from a wide variety of disciplines. The sites with appreciable continuity include those of Kummer, Abbeglen, and colleagues with hamadryas baboons in Ethiopia; Ransom, Packer, and others with the olive baboons at Gombe in Tanzania; the Altmanns, Hausfater, and colleagues with the yellow baboons in Amboseli, Kenya; Harding, Strum, and others in Gilgil, and more recently Popp and DeVore at Mara, all with olive baboons in Kenya; W. J. Hamilton with chacmas in Botswana; and the Rasmussens and Rhine with yellow baboons in Mikumi, Tanzania.
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My daughter has to do a report on the Golden Monkey(not any kind of group but the "Golden Monkey". We are having a hard time finding any information. Is their another name for this type of monkey, or do you have an idea where we can go to find this information. Thanks
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Baboon Mothers and Infants by Jeanne Altman excerpts part 5
General Natural History
Savannah baboons are born into semiclosed groups of about 40 animals, but ranging from less than 10 to almost 200. In the wild, baboon females reach menarche at four-and-a-half to five years of age, and then before their first conception they experience a series of menstrual cycles for about a year ("adolescent sterility"). Their infants are born after a gestation period of six months (177 days). Postpartum amenorrhea follows, such that successive infants are produced at intervals of one-and-a-half to two years unless the process is accelerated by the death of the previous infant. Thus, after a female reaches full maturity, that is, experiences her first pregnancy, she spends approximately half her life with a dependent infant, almost a third of her life pregnant, and the remaining time undergoing menstrual cycling. This is true throughout adulthood; menopause has not been demonstrated for any nonhuman primate.
The Amboseli Population
The cynocephalus, or yellow, baboons include those we studied in the short-grass savannah region of southern Kenya just a few miles north of Mt. Kilimanjaro. There they inhabit Amboseli National Park along with a wide variety of other animals. Some of these, such as leopards, lions, and most recently hyenas, prey on baboons. The baboons themselves prey on others. These prey are usually grasshoppers and other invertebrates, but, they also include African hares, gazelles, and vervet monkeys, especially during the dry season. Most other large mammals in the area, such as elephants, wildebeest, and zebras, have an essentially neutral relationship with baboons, or an indirect one, through plants.
The Amboseli baboons have two sources of contact with humans other than the observers. First, Maasai pastoralists live within the animals' home range during the dry seasons. Although the Maasai seldom overtly interfere with most wildlife, their cattle constitute a large proportion of the Amboseli biomass during the dry seasons and compete with other grazers. Baboons, along with other wildlife, are displaced by cattle herds. Additionally, Maasai dogs and children occasionally chase baboons. Since late 1976, the Maasai have been excluded from Amboseli National Park in exchange for services and alternative resources, and have been provided with financial compensation for allowing wildlife to graze on Maasai land outside the park. Contact between baboon groups and Maasai and the effect of competition with Maasai cattle are now restricted to portions of the baboons' home range that are outside the park.
Second, tourists visit Amboseli. In recent years the number of tourists has greatly increased; but in contrast to the tourists of the early 1960s, these visitors are usually non-Kenyans and often on commercial tours. The result is that they spend little time in the park, almost all of it within a small area near the lodges, several miles from our main study area. Thus, members of our main study group currently seem to come in contact with tourists even less than study groups did when we first worked in Amboseli in the early 1960s.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 6
Western and van Praet (1973) have described the recent transformation of the Amboseli habitat from an acacia woodland to a dry habitat with salt-loving plants. Several years of heavy rainfall during the 1960s raised the water table to unusually high levels. The rising water led to the death of most of the trees in the acacia woodland. Some trees died as a result of salts, which, through "wicking action," form a layer in the soil just above the water table and are carried up into the root zone of the trees. The roots of other trees were completely drowned. Overgrazing by large herds of Maasai livestock reduced available grazing material, and this depletion, in turn, probably resulted in a shift in diet of animals that are both browsers and grazers, most notably elephants, and led to further damage to trees. Overgrazing was aggravated by poor rainfall starting with a drought in 1969.
As a result, major declines occurred in populations of many species of wildlife that depend on woodland habitats, including the vervet monkeys. Over two thousand baboons were censused in the Amboseli waterhole area during 1963-64, but by 1971 the baboon population in the same area was only about 10 percent that size. The percentage decline in the baboon population was considerably greater than that of the vervets (90 percent versus 33 percent), at least partially owing to the trapping of approximately 230 baboons in 1965 by the Southwest Foundation for Research and Education; also probably partially owing to the presence of a paralytic virus in the population in 1964.
In 1971 we began a general program of periodic monitoring of the baboon population as a whole and longitudinal monitoring of demographic events in a single study group. A detailed analysis of the baboon population since 1971 is under way but the most relevant demographic data for the subjects of the longitudinal study, Alto's Group, are described here.
Alto's Group
The subjects of this study and of most of our detailed longitudinal observations are members of Alto's Group, one of five groups now occupying the central waterhole area of Amboseli. Longitudinal data on individuals in Alto's Group have been collected since 1971 by a succession of field workers. In the fall of 1972, a fusion was completed between the original Alto's Group and a one-male group, High Tail's Group.
Of the 35 members of Alto's Group in July 1971 and the 15 members of High Tail's Group when they were first censused in November 1971, 23 from Alto's Group and 8 from High Tail's Group remained in the combined Alto's Group of 47 members four years later, at the onset of this study in July of 1975. Thus there was approximately a 40 percent turnover of group members from 1971 to 1975. This turnover was due to births, deaths, and migrations. Of course, even more such demographic events occurred during the intervening years than are indicated by these figures, since many individuals were born and died, joined the group and then either died or emigrated, and so on. Consider Dogo, an infant born to female Preg in August 1971. He has grown up in an ever-changing social group and has known approximately 68 animals, while staying in his natal group of about 45 animals. None of his cohort from 1971-72 remained in Alto's Group in 1975; yet almost all of his younger sister's 1973 cohort did. Most of those who were juveniles when he was born were still in the group in 1975, though some males had temporarily emigrated and then returned. Of the eight males who were fully adult when Dogo was born, only three, Peter, Max, and Stubby, remained. In January 1979, Dogo was just reaching adulthood when he was killed by two hyenas. At the time of his death, he was the oldest animal that we knew from birth. His mother and two younger sisters remained in the group; a younger brother, Pedro, one of the subjects of the current mother-infant study, died when eight months old.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 7
In the results of this study I document a more complicated picture of motherhood and infancy than has usually been considered. Yet I still deal primarily with only one year and one reproductive stage in the lives of adult females: their last month of a pregnancy and the first year of their infants' lives. Occasionally I shall hint at the longer view: relationships established before infants' birth, bonds that persist for infants as they mature, lifetime dominance relations, and long-term ecological patterns. Many of these are currently topics of Amboseli research conducted by Stuart Altmann, Glenn Hausfater, David Post, David Stein, and Jeffrey Walters. However, the continuities and the long-term bonds will also be set against the ever-changing demographic panorama.
Each year approximately ten infants are born into the group of about 45 animals. Usually six or seven infants survive the first year of life. In recent years, Alto's Group has remained at a fairly stable population level, and on the basis of age-specific birth and death rates, we predict that this stability will continue. These were essentially the demographic conditions during the study of mothers and their newborn infants that I conducted from July 1975 through July 1976, during October 1976, and during a short pilot study in 1974.
The Mother-Infant Study
All females in Alto's Group who had infants under a year of age were included in the study. Except for one adult female, Lulu, who has not conceived since at least 1971, probably not since 1969, all adult females in Alto's Group had at least one infant during this study, including four primiparous females and two females who experienced their first viable delivery during this period. Infant maturation and mortality factors resulted in three females being included with two successive infants. Five infants who were included were born before July 1975. Thirteen others were born during the study.
When I arrived in Amboseli at the end of June 1975, several infants were already in the group. Information about them was kindly provided by David Post and Jane Scott. The oldest was Pooh, a scrawny eight-month-old female with locomotor impairment who was Plum's first-born. Several other infants were born about the same time as Pooh and would have been included in the study if they had survived. Slinky's first infant was stillborn in November. Brush's first infant was born in October with congenital deformities; it lived only a few weeks. A high-ranking older female, T.T., had given birth to a healthy male infant, Tom, within a week of Pooh's birth. I was quite disappointed when we learned of T.T.'s and Tom's sudden disappearance in May.
Four females gave birth within two weeks at the end of 1974, when Pooh was about two months old. Alice was born to high-ranking, elderly Alto, who had two other known surviving daughters in the group, Spot and Dotty. Another high-ranking older female, Mom, also gave birth to a daughter, Softy at that time, but Softy died of unknown causes after only a few weeks. Mid-ranking Oval and Fem both gave birth to sons, Ozzie and Fred. Oval's juvenile daughter, Fanny, was in the group. Being Fem's first infant, Fred had only one "known" relative, his mother's putative sister, Gin.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 8
In addition to Pooh, Alice, Ozzie, and Fred, two-month-old Eno was already in the group when I arrived. Early one evening in late April she was born to Este, an elderly low-ranking female who had a five-year-old son, Toto, in the group when Eno was born. We had expected Eno to have a close peer, because Judy, another elderly low-ranking female, was due to give birth in March. However, Judy temporarily disappeared from the group at about that time, and was wounded and apparently experienced a stillbirth before her return. At the end of June Slinky gave birth to her second infant. Although it apparently was well formed externally, it was rigid at birth and died two days later.
In July Pooh, Alice, Ozzie, Fred, and Eno were joined by Summer and Pedro, offspring of mid-ranking Scar and Preg, who already had surviving offspring in the group. In August, Misty and Bristle were born, within a few days of each other. Misty was the daughter of high-ranking Mom. Bristle was Brush's son, and since Brush's first infant had died so early and had been malformed, it was almost as if Bristle was her first-born. The fact that Brush was very low-ranking made a striking contrast in the experiences of these two infants, one that had not been so evident with the more closely matched Summer and Pedro. Misty's death just after she turned two months old was a particularly unfortunate one.
Just before Misty's death, Handle, a low-ranking female, gave birth to her first infant, Hans. Hans's environment was quite similar to that of Bristle. Since their mothers were also rather frequent associates and since no other infants were born until late January, these two infants spent much time together.
Starting in late January, four infants were born within a month of each other. Gin gave birth to her first infant, Grendel. A few days later, Slinky finally gave birth to a viable infant, although Sesame appeared weak from birth and had bouts of illness periodically thereafter. At the end of February, Judy again gave birth, this time to a healthy son, Juma. Judy's daughter, Janet, was almost three years old by then. A few days later, Alto's daughter, Spot, also high-ranking, gave birth to female Safi. With two sisters and a grandmother in the group, Safi had more known relatives than any of the other infants.
Several months passed. One night during this period Judy and Juma disappeared and did not return. Then at the beginning of June, Mom gave birth to Moshi. I was struck with how similar Moshi's world was to that of his sister, Misty, and how different it was from that of infants such as Bristle who had been born at the same time as Misty. Similar contrasts were evident among the other infants. I shall explore the nature and origins of some of these differences in the chapters that follow. Often Bristle and Moshi will provide useful examples of contrast.
Just after I left Amboseli at the end of July, Ozzie's younger sister, Oreo, was born. When I returned to Amboseli for a month that October I was able to observe Oreo as well as Vicki and Peach, who were born at the beginning of October. Despite over a year of observations on new mothers, including the first day of life for most of the infants, had not actually been present for a birth. It was a particularly exciting surprise when the last birth, that of Plum's infant, Peach, occurred while I was making observations one afternoon, and when Plum, the most wary female in the group, tolerated my presence at a moderate distance, enabling me to watch most of the labor and birth.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 9
BECAUSE MOTHERS WITH NEONATES appear to be the class of individuals in our baboon population that are most sensitive to being observed, and because most of our previous research had been done from atop a vehicle, the first month of this study and to some extent the second were partially devoted to accommodating the females to observation on foot within 5 to 10 meters. Much closer distances were possible for most mothers, but consistent with the aim to minimize our effect on the system we were studying, I always tried to stay at a distance that would not discourage the mothers' interactions with the most sensitive individuals in the group. In addition, some types of detailed data were considered sufficiently reliable to use only after several weeks or more of systematic sampling. Consequently, for some analyses I used data obtained from July 1975 onward; for others, only data obtained later.
After various sampling schemes were tried, the following scheme was established by September 1975. Each female was sampled during the last month of pregnancy for two days at least a week apart, on the day of birth and the fifth day of infant life, on two days during the infant's second week, and one day per week thereafter until the infant was six months old. During the next six months samples were taken two or three days per month. Whenever impassable mud, illness, or other factors reduced available observation days, sampling mothers with older infants was sacrificed in favor of sampling those with younger ones.
In gathering behavioral data I sought samples that would provide unbiased estimates of rates of behavior, of time budgets and bout durations, and other measures that are derived from these.
Focal-animal (continuous) sampling and instantaneous (point) sampling are the most versatile and suitable of the common techniques used to provide unbiased estimates of time budgets; focal samples provide the data needed to estimate rates and bout durations. Unfortunately, until recently most field studies have utilized ad libitum sampling and many laboratory studies one-zero sampling, neither of which provides unbiased estimates of these parameters. Detailed comparisons of bouts, rates, time budgets, and derived measures within and between studies that utilize these techniques cannot be made unless the sampling scheme itself is considered as a possible source of the differences and similarities found in the results. Consequently, I shall primarily restrict detailed comparisons between the results of this study and others to those comparisons not likely to be confounded by sampling biases. More generally, I shall emphasize where possible, comparisons with those studies that differ in the fewest major variables, such as species and extremes of caging and rearing conditions, so that similarities or differences can be at least provisionally attributed to characteristics of the animals in their normal range of living conditions.
On each sample day, I sampled the behavior of two females. They were sampled alternately, each for 15 minutes in-sight time (or 20 minutes in the first months of the study) out of every hour from 0800 through the 1700 hour but excluding the 1200 hour. The females that were sampled on any one day were paired on the basis of proximity in age of their infants. Such pairing provided the possibility of control for variability in factors such as day journey length or unusual daily events and enabled me to sample females more frequently than if I had followed only one female per day. Alternating between two females did have the disadvantage that more time was devoted to searching for individuals and probably more of the 15-minute samples were missed altogether than would have been the case if I had stayed with just one female each day.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 9
BECAUSE MOTHERS WITH NEONATES appear to be the class of individuals in our baboon population that are most sensitive to being observed, and because most of our previous research had been done from atop a vehicle, the first month of this study and to some extent the second were partially devoted to accommodating the females to observation on foot within 5 to 10 meters. Much closer distances were possible for most mothers, but consistent with the aim to minimize our effect on the system we were studying, I always tried to stay at a distance that would not discourage the mothers' interactions with the most sensitive individuals in the group. In addition, some types of detailed data were considered sufficiently reliable to use only after several weeks or more of systematic sampling. Consequently, for some analyses I used data obtained from July 1975 onward; for others, only data obtained later.
After various sampling schemes were tried, the following scheme was established by September 1975. Each female was sampled during the last month of pregnancy for two days at least a week apart, on the day of birth and the fifth day of infant life, on two days during the infant's second week, and one day per week thereafter until the infant was six months old. During the next six months samples were taken two or three days per month. Whenever impassable mud, illness, or other factors reduced available observation days, sampling mothers with older infants was sacrificed in favor of sampling those with younger ones.
In gathering behavioral data I sought samples that would provide unbiased estimates of rates of behavior, of time budgets and bout durations, and other measures that are derived from these.
Focal-animal (continuous) sampling and instantaneous (point) sampling are the most versatile and suitable of the common techniques used to provide unbiased estimates of time budgets; focal samples provide the data needed to estimate rates and bout durations. Unfortunately, until recently most field studies have utilized ad libitum sampling and many laboratory studies one-zero sampling, neither of which provides unbiased estimates of these parameters. Detailed comparisons of bouts, rates, time budgets, and derived measures within and between studies that utilize these techniques cannot be made unless the sampling scheme itself is considered as a possible source of the differences and similarities found in the results. Consequently, I shall primarily restrict detailed comparisons between the results of this study and others to those comparisons not likely to be confounded by sampling biases. More generally, I shall emphasize where possible, comparisons with those studies that differ in the fewest major variables, such as species and extremes of caging and rearing conditions, so that similarities or differences can be at least provisionally attributed to characteristics of the animals in their normal range of living conditions.
On each sample day, I sampled the behavior of two females. They were sampled alternately, each for 15 minutes in-sight time (or 20 minutes in the first months of the study) out of every hour from 0800 through the 1700 hour but excluding the 1200 hour. The females that were sampled on any one day were paired on the basis of proximity in age of their infants. Such pairing provided the possibility of control for variability in factors such as day journey length or unusual daily events and enabled me to sample females more frequently than if I had followed only one female per day. Alternating between two females did have the disadvantage that more time was devoted to searching for individuals and probably more of the 15-minute samples were missed altogether than would have been the case if I had stayed with just one female each day.
Brad and Trouble
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Baboon Mothers and Infants by Jeanne Altman excerpts part 10
AGE DIFFERENCES BETWEEN SIBLINGS, the size and age-sex composition of available play groups, and other important features of the social milieu of mothers and infants are determined by the demographic patterns of a populationùage-specific rates of natality and mortality, migration, and so on. Mortality figures in particular provide clues to stressful life stages and are important in considering costs and benefits of various social behaviors within an evolutionary framework.
Survival of Infants, Juveniles, and Adult Females Of the 13 infants who were born during the study, 3 (Pedro, Misty, Vicki) died during the study after varying periods of illness, 1 (Juma) suddenly disappeared overnight with his mother during the study, 1 (Safi) became seriously ill and recovered, and 3 (Sesame, Moshi, and Peach) died after the study but during the first two years of life, that is, as infants (first 12 months) or in the beginning of the juvenile period. Six (Summer, Bristle, Hans, Grendel, Safi, and Oreo) survived the first two years of life, 2 of them (Bristle, Oreo) as orphans. Of the 5 infants who were included in the study but who were born before July 1975 (i.e., had already survived part of the first year when the mother-infant study began), 4 (Alice, Ozzie, Fred, Eno) survived through the second year of life and 1 (Pooh) died just before her second birthday. Alice was orphaned before her second birthday; Ozzie after his.
Only rarely can we determine either the immediate cause of death or an earlier precipitating cause. When an apparently healthy female or young juvenile disappears from the sleeping grove overnight we presume not only that it died but that it was probably taken by a. However, in the case of older juvenile, subadult, and adult males even overnight disappearances can be due to migration rather than death, a fact that makes it difficult even to construct life tables for these age-sex classes. Determination of an infant's death is somewhat easier because if it is survived by its mother, she usually carries the corpse for several days. Of the infants in the 1975-76 study Peach and Misty apparently died of disease; probably Pedro and Juma did as well, along with Juma's mother, Judy. Vicki's death was probably due to poor mothering, and Pooh's to the severe wounds inflicted by male Even just before her second birthday. Both Moshi and Sesame showed signs of possible nutritional deficiencies for at least a year before they died. Sesame disappeared just before her second birthday and soon after the birth of her mother's next infant. Moshi fell from a tree when his younger brother was a few months old The cause of his fall is unknown. Alice's mother, Alto, disappeared while we were away from the group for several days. When we first identified Alto in 1969, she appeared to be old, probably at least 15 years of age; during the last months of her life she seemed to become less interactive and to rest more.
Mortality patterns during the year of the mother-infant study were similar to those for the whole seven-year period of the longitudinal study; we can analyze the latter in greater detail because of the larger sample sizes. Sample sizes are now about twice those available in our earlier paper on infant survivorship, and data are now available for years two through five, taking females through the age of menarche and males almost to the beginning of subadulthood. In addition, the mortality data considered here come entirely from a period of fairly stable demographic parameters. No trends in survival could be detected when I examined infant mortality within Alto's Group from each year separately, and I have therefore combined the data since 1971 to provide more adequate sample sizes for the analyses that follow.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 11
Several features of the survival data are quite striking. Mortality is appreciable (.28) in the first year of life and only slightly less so (.25) in the second year. However, it is essentially zero in the next three years. (One juvenile male, Kub, either died or migrated in the fourth year.) Baboon mothers provide little care during an offspring's second year of life, often none during the latter part of that year. The low survival rates during the second year of life suggest that a prolongation of maternal I care might potentially be of considerable benefit to these offspring and I increase their rates of survival. By contrast, in the third, fourth, and fifth years, which are still prereproductive years, the survival rate is virtually 100 percent. Consequently, it seems unlikely that directing any additional care or "altruistic" behaviors of immediate consequence toward these older juveniles would result in a selective advantage: there is no potential survival difference that could provide the selective basis for the evolution of such behaviors. However, behaviors of long-term or delayed consequence, such as those affecting age of menarche, ability to obtain mating partners, or ability to learn parental skills, may be of advantage to this age group.
In early research , the period of infancy was considered to be the first year of life. However, from our longitudinal study we have since found that individuals identified as older infants by physical appearance and by the fact that they are still suckling and are associated with a single adult female, are up to 16 months of age. Baboons are not strictly seasonal breeders, interbirth intervals are individually variable, and the development of independence is a long, gradual process that extends into the second year of life. Thus it is difficult and somewhat arbitrary to define the age limits of infancy. All of the first year of life is clearly a period of dependence and infancy. This study focuses on that period and it is individuals of that age that I refer to as infants. However, considerations such as the mortality data above and mothers' future reproduction demonstrate the importance of the second year of life, and where possible, I extend my discussion to this period.
Consider next mortality risks for females during adulthood. In the seven years since mid-1971, we have data for approximately 78 female-years of exposure for fully mature females, defined as those who have conceived at least once. Nine fully adult females died in Alto's Group during the period from September 1971 to September 1978, for a mortality rate of .12 per annum. In most mammals mortality risk is low in the early years of adulthood, but rises, often rather sharply, in later years. Is mortality risk a function of age among adult female baboons? In particular, is the mortality risk to mothers age-related? Young adult females (taken here as those who have conceived at least once but who were within three years of first conception, that is, those who were approximately six to nine years old) had an annual death rate of .04; older ones (defined as those who were at least three years past first conception) a rate of .16. Adult females usually spend approximately one-half of their adult lives with a dependent infant under a year old the proportion is slightly lower if the infant dies, higher if the infant survives. Thus, one would expect mothers of infants to account for half of the deaths among adult females. In fact, six of the nine females who died had infants under a year of age at the time of death, for a rate of .15 deaths per annum for females with an infant. The rate for females without an infant was .08 per annum. Of these remaining three deaths, one was a young female (Brush) experiencing her third pregnancy. The other two were much older females who were experiencing abnormal reproductive cycles: in Jane's case, a particularly long cycling time without becoming pregnant, and in Alto's an unusually long postpartum amenorrhea. Perhaps their deaths resulted from or were made more likely by pathology or old age. The tentative conclusion is that in this population reproduction exacts a substantial cost in the form of increased mortality.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 12
It is reasonable to expect that two additional variables might affect the survival of mothers or infants: maternal dominance rank and infant gender. seven years, sex ratios at birth have been equal (26 males :26 females, plus two unsexed stillbirths and one unsexed case of neonatal death during late 1972). Infant (first-year) mortality, including stillbirths, was higher for male infants than for female infants. This difference does not approach statistical significance, and was due almost entirely to the fact that four of the male infants and only one of the female infants died at the same time that their mothers did. We cannot yet tell whether this latter result is an artifact or whether, for some reason, mothers of male infants are more vulnerable. Although these mothers were all older mothers, older mothers, like younger ones, produced infants at about a 1 :1 sex ratio. For humans, sex ratios at birth are slightly skewed toward males and become less so for older mothers or those of higher parity, but a sharp skewing in favor of males occurs for quite old mothers. We do not yet have sample sizes 18 for the baboons adequate to detect differences of the small magnitude found in humans.
It is generally assumed that female dominance rank is correlated with reproductive success. Although this has not yet been demonstrated for savannah baboons, there is some positive evidence for provisioned macaques and perhaps - for geladas. Female offspring assume their mother's relative dominance rank for life, whereas male offspring repeatedly change rank during adulthood and seem to be less affected, as adults, by their mother's rank, as has been reported for macaques.
As predicted on the basis of the behavioral life history results described above, in Alto's Group dominance rank is related to sex of off spring: low-ranking mothers produce more male than female offspring, high-ranking ones producing primarily female offspring. We can make a dichotomous characterization of these mothers as high- or low-ranking. Then we can also make a dichotomous characterization on the basis of whether a female had more male or more female offspring, considering each mother as the sampling unit, rather than each birth, in case there is a lack of independence of sex among offspring of the same female. The results (omitting ties) are that five or seven high-ranking females had more female than male infants, and five of seven low-ranking females had more male than female infants. Alternatively, if we do consider each birth as an independent sample and incorporate the two rank changes, we see that 10 of 29 infants born to high-ranking females were male, but 15 of 22 infants born to low-ranking females were male. Although I know of no literature on the possible mechanism leading to this result, physiological differences due to differences in stress levels could perhaps result in differential sperm survival in the two groups. The observed sex difference of offspring would appear to be the best strategy for each type of female, if female dominance rank is correlated with reproductive success, with female offspring of high-ranking mothers retaining their mother's rank and male offspring of low-ranking females being "freed" of their mother's rank. The relationship between maternal rank and sex of offspring has been modeled by Trivers and Willard (1973), and the model I am proposing for the observed baboon sex ratios is in the same spirit. However, this social and reproductive system requires a different set of assumptions than those used by Trivers and Willard; and therefore different specific predictions result.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 13
From the results that survival rates were as good or better for female (versus male) infants, and that high-ranking females tended to produce female offspring, one would expect to find that offspring of high-ranking females have lower mortality rates than those of lower ranking females. However, rates of infant mortality were slightly but not significantly lower for infants of low-ranking mothers (6 out of 20 = .30) than for infants of high-ranking mothers (9 out of 23 = .39). Thus despite the facts that low-ranking mothers produce more male than female offspring, high-ranking ones produce primarily female off spring, and female infants have survival rates as high as or higher than those of male infants, infants of high-ranking mothers have no higher, and perhaps somewhat lower, survival rates. This contra intuitive result for infant survival rates contradicts the limited available primate data on reproductive success from two provisioned rhesus colonies, as well as data on survival of human infants in different socioeconomic classes . However, even though infant survival does not appear to be positively correlated with dominance rank, other factors affecting the female's reproductive success, such as age of menarche and length of interbirth interval, may be rank related in our population. Only future study will clarify this puzzling situation.
When we combine the various pieces of information on maternal and infant mortality, the suggestion emerges that young adult females, essentially those with their first or second infant, are about as likely to have that infant survive and are more likely to survive themselves than are older females. Older females are more likely than are younger ones to die during the period of infant care, in which case the infants will also die. However, if these older mothers survive, their infants are also very likely to survive. Thus, their fate, more than that of young mothers, is closely linked to that of their infants during the first year.
Perhaps a cautionary reminder is necessary at this point. Some of the foregoing results have been obtained by partitioning a small data set, resulting of course in smaller subsets. Also there are several factors that may lead to differential exposure to the various reproductive stages, including the very results just discussed. There is at present no way to remove such confounding completely. Patterns will, one hopes, become clearer as more data accumulate. Sample sizes are not yet adequate to confirm statistically even appreciable differences.
Not only do infants affect their mothers' survival chances, but infants additionally affect demographic processes in a primate group in general and their mothers' reproductive success in particular through the direct effect that infants have on their mothers' future reproduction. Mothers of surviving Amboseli infants experience approximately 12 months of postpartum amenorrhea and then take an average of four cycles to conceive, whereas infant death results in resumption of cycles within one month of the death and conception after only one or two cycles on the average. It has been further suggested that mothers could improve their reproductive success if they reduced infant care, for example, by weaning their infants, thereby reducing the length of postpartum amenorrhea. While this has certainly been the case among humans in developing countries in recent years, such a result is dependent on (1 ) infant mortality rates not being appreciably increased by early weaning and (2) the mortality risk of childbirth and early stages of infant care being low. Weaning foods and even a semblance of modern medicine are probably sufficient to satisfy these conditions in developing countries. It is unlikely, however, that these conditions prevailed until recently for humans, or that they are satisfied in most animal habitats, including that of the Amboseli baboons. It is quite possible that in the absence of such advantages of early weaning females obtain higher reproductive success by engaging in fairly long periods of infant care than they would by reducing the period spent caring for a current infant in order to reduce the interbirth interval.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 14
A per annum mortality rate of almost .30 occurs during each of the first two years of life, with mortality dropping to virtually zero in the several years thereafter. Thus infancy and the following year are particularly crucial and difficult periods. The data also suggest that older adult females suffer higher mortality rates than do younger ones. This general pattern is the common mammalian one only the sharp discontinuity at age two may be unusual. Dittus' study of Macaca sinica (1975, 1977) provides the only comparable mortality data for a non-expending natural primate population. His data exhibit the same U-shaped distribution. Dittus' life-table data come from one cross-sectional census of many troops. Age was estimated by physical appearance, for immatures by making use of the short, discrete birth season in this species, and by comparisons with longitudinal changes in a smaller set of known individuals studied for several years. The life table data that Dittus presents (1975:132-138) agree in general with those reported here, with high rates of mortality for infants and for older adults, low rates for older juveniles and young adults. The one striking difference that merits comment here is the much higher mortality rate Dittus reports for young female versus male infants at his site in Polonnaruwa. However, this finding is based on the assumption that the 1970-71 sex ratio at birth was 1 :1. Although known births for four years averaged a 1 :1 ratio, the ratio reported for the Polonnaruwa region for 1970-71 is 21 :14, or 3:2, essentially the same ratio found in the infant-2 (older infant) class during the census. Thus it is not clear from the available data that differential female mortality occurs among the infants of that population. Subsequent data from the longitudinal project there should clarify this issue.
Additionally, in Amboseli there is a cost of reproduction. That is, females, especially older females, with dependent infants tend to suffer higher mortality rates than do younger ones or those in other stages of the reproductive cycle. I know of no published data on the cost of reproduction in other wild primate populations. Infants may impose an additional cost on their mothers' future reproduction due to an extended period of postpartum sterility, but this will depend on the risks mothers and infants would incur as a result of early weaning. Thus mortality risks are high for both mothers and infants. In the following chapters I shall attempt to identify those ecological and social factors that shape the first two years of life and in particular those that may enhance or hinder the survival of mothers, infants, and young juveniles and affect their interactions.*
* Deaths of adult females (four) and births (six to multipara and 5 to primipara) from 1 August 1978 through 31 December 1979 provide increased evidence for (1) the susceptibility of adult females to death when they have infants and (2) the relationship between maternal dominance rank and infant gender.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 15
IN RECENT YEARS time and energy have figured prominently in minimization or maximization models in behavioral ecology. However, the importance of time may be much more general than is suggested by minimization models. All of an animal's basic activities require time to perform; some of them require considerable amounts of time. Moreover, time is quite limited and all activities must be carried out within a fixed number of hours: baboons spend all 10 of the dark nighttime hours resting and sleeping in the trees, plus 3 to 4 additional late-evening and early-morning hours. Ten to 11 hours remain. I suggested previously that these daytime hours are filled to a considerable extent by maintenance activities. As a key to understanding the demographic results of the preceding chapter and the constraints within which mothers live, l shall now consider these daytime time budgets in detail and the ways in which the presence of a dependent infant influences a mother's productive activities.
Seasonality of Time Budgets
The Amboseli habitat is subject to considerable seasonal variability. As expected from its latitude (2 40'S), there is little variability in day length and temperature range, but seasonal variability in rainfall is considerable. The period from May or June through October is usually characterized as the long dry season, November and December as the short rains, January and perhaps February as the in terrains, and March through April or May as the long rains. Despite some variability from year to year, this basic pattern persists in Amboseli. During the dry season the baboons depend on the few permanent water holes in the central area of the park. When the rainy season arrives, however, temporary rain pools are available throughout their home range. At that time most large mammals in the area migrate out of the park, while others, such as the baboons, alter their habitat usage and movements within the same basic area. During 1975-76 the distance : traveled by the baboons was greatest (almost 6 kilometers daily) in December, January, and September. The values were lowest during the rainy season (4 to 4.5 kilometers). Time spent walking showed a some-what similar pattern, with highs of over of 17 to 19 percent in August, February, and March. Variability in feeding time was even greater, with 52 to 55 percent of the time spent feeding during June through November (the rains arrived in late November in 1975) and averages of only 40 to 42 percent during December, January, and May, with a gradual rise after January but a very sharp rise from May to June and for the rest of the dry season.
The effect of rainfall patterns on the group movements and on the percentage of time the baboons spend feeding and walking is a complicated one. Baboons are, and their various foods are distributed differently throughout their habitat and have different seasonal growth patterns. Particular food plants in particular parts of the animals' habitat leaf or fruit at various times after the onset of the rains. Then, too, some of these plants fruit annually, a month or two after the onset of one of the rains, whereas other plants, such as the grasses, develop lush new growth soon after the onset of each rainy season. Thus, in a linear regression, monthly rainfall accounted for less than 20 percent of the daily variance in distance traveled, and distance traveled or the time spent walking were no better as predictors of the time spent feeding. However, the average distance traveled by the group in a month accounted for 75 percent of the variance in the average time mothers spent walking that month. Also the sum of the rainfall in a month plus that for the previous month accounted for 50 percent of the variance in average monthly time spent feeding. That is, cumulative rainfall was a good predictor of the time an individual spent feeding, and the length of the group's day journey was a good predictor of the time an individual spent walking.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 16
The patterns of seasonal variability in day journey length and in the percentage of time spent feeding and walking are essentially the same as those found for 1963-64 for day journey length. Thus it seems reasonable to assume that these environmental conditions represent a pattern that is repeatedly encountered by the baboons from one year to the next, with relatively small annual variations, and that these conditions may be of considerable importance to the energetic requirements of lactating females, to the development of infant independence, and to the survival of both mothers and infants.
Synchrony of Activities within the Group
To what extent is the length of the group's day journey o; the amount of time an animal spends feeding determined by any individual and to what extent are an individual's activities determined by those of other group members or the group as a whole? We can assume that neither any individual nor the group as a whole affects short term rainfall patterns. Yet there remains some amount of flexibility in the amount of time spent feeding, and an individual may influence day journey lengths as well as vice versa. Survival differences may well depend on the extent to which environmental and social constraints combine with reproductive ones to place more or less burden on a female. Likewise, the degree of an individual's ability to affect these variables herself may well make a crucial difference to her survival.
Probably of particular importance to new mothers is the length of the day journey on the infant's first days of life. The infant often has trouble clinging during these first few days, sometimes requiring its mother to walk three-legged while pressing the infant against her ventrum with one hand, or to perform frequent repositioning during long marches. Especially on the infant's day of birth, the mother seems quite tired. This is reflected in her time budget for that day, during which she spends much more time resting than usual, and in the lack of concordance between her activities and those of other group members, discussed below.
Day journeys on days of birth were not likely to be shorter than average for the month, despite the mother's fatigue (6/10 lower than the mean, 5/9 lower than the median). Somewhat more of an effect is seen by comparing mean day journey length for the week before the day of birth with that of the week beginning with a birth day. The magnitude of the differences was small, but the direction of the effect was such that in six of eight cases for which had these data the distance traveled was shorter in the week following infant birth than in the previous week. It remains for further study to determine whether this slight effect is in some sense real (would reach statistical significance with somewhat larger samples) and if so, whether the magnitude is sufficient to be of any benefit to mothers. New mothers are sometimes seen dragging along at the rear of the group and thereby may be exerting a slight effect on the route, but there is no evidence that the group makes appreciable alterations in its activities to accommodate new mothers. If anything, during the early months of infant independence mothers probably spend more time walking than do other group members, because they spend time retrieving their infants.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 17
I expected that the percentage of time spent feeding, or feeding plus walking, would be a function of maternal dominance rank, with low-ranking females spending more time in these activities than do high-ranking ones. This was predicted on the assumption that low-ranking females would more frequently be displaced from high-quality foods and would therefore need more time to obtain an adequate amount of food. There was no such significant effect on feeding time, nor was there in Post's limited data on this topic. If a small but consistent effect does exist, the data are not yet adequate to detect it. Dominance effects may occur only during the dry season. The data from this study could not be analyzed by season owing to the confounding effects of infant age. This remains a problem for future research..
In approximately 90 percent of the samples the focal animal's predominant activity was the same as that of the group. Almost all deviation from that 90 percent figure occurred during the first month of infant life, when there was only 80 percent concordance. Most of this deviation, in turn, occurred on day one of infant life, when there was less than 60 percent agreement. This lack of concordance was due to the fact that mothers fed much less on day one and rested much more. I do not know whether the lower amount of time spent feeding on that day is the result of fatigue and of the difficulty in feeding due to the need to use one arm much of the time for infant support, or whether the afterbirth, which is eaten, supplies sufficient nutrients to allow less feeding that day. On the fifth day of infant life, residual discordance was still produced, partially by new mothers' doing more resting but also by their socializing more, as was true for the rest of month one. The rare instances of lack of concordance in later months were not consistently due to any particular activities.
Effects of Infants on Mothers' Feeding Patterns
In Amboseli the baboons feed while in either a seated or a quadrupedal standing position. Whereas catching insects and feeding on berries are probably more easily done from a standing position, two handed feeding is done primarily while sitting and may be advantageous for obtaining some foods, such as grass corms. Although it also appears that feeding while seated is more relaxing and energetically economical, the animals frequently have to move from one food patch to another. Some of these movements are caused by other group members, others by depletion of the present food patch. In either case, the seated animal must stand again with each move. However, during the first few months of an infant's life, if its mother is seated the infant can maintain contact and even doze without clinging and having to support its weight. After many hours of riding on the mother's ventrum, very young infants often tire and have trouble clinging. During the second month the infant can explore with considerable safety within its seated mother's ventral flexure. By the third month an active infant in her ventrum clearly hinders a mother's feeding attempts, and I often observed a mother embrace her infant to passive clinging, push it gently outside her ventrum (and just out of contact but nearby), or stand and feed with the infant exploring under her torso. Mothers of infants that were over five months old stood while feeding slightly more often than they sat; mothers of three- to five-month-olds were about as likely to sit as to stand, with considerable variety of direction from month to month and individual to individual. However, during the first month of infant life all nine mothers sat while feeding more than they stood and eight of nine mothers did so during month two. There were no differences on the basis of maternal dominance rank. Thus a mother's feeding positions seem to be an accommodation to her infant's needs during the first months, but gradually she prevents her infant from hindering her feeding by modifying her infant's behavior and sometimes modifying her own. By month four infants are disproportionately out of contact when their mothers feed.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 18
Maternal Time Budgets and Infant Gender
I can discern no significant effect of infant gender on the time mothers spend feeding or feeding plus walking. However, during all but one month mothers of female infants averaged slightly but insignificantly more feeding time than mothers of male infants. A gender effect resulting in more time spent feeding by mothers of male infants would be expected primarily if male infants grow faster than females. (Adult male baboons are about twice the weight of females.) A differential in the opposite direction would be predicted if males became nutritionally independent on their mothers earlier. The literature is contradictory on the former point for the first year of life for baboon and macaque infants kept in laboratories. Snow's data (1967) indicate no sex difference in growth rates until the end of the second year. Yet for rhesus macaques, Macaca mulatta, and another baboon colony there are indications that differences in growth rates may exist earlier, with male infants gaining weight more rapidly. During the first year of life, the infants in this study exhibited no consistent visible size differences: female Alice and male Ozzie were approximately the same size; same aged male Fred was smaller; two-month-older female Pooh was smaller; female Eno, who was four months younger than Alice, Ozzie, and Fred, was about Fred's size; and so on. With respect to earlier nutritional independence of one sex, there were no obvious qualitative differences, but the results of S. Altmann's nutritional study of baboon infants (in preparation) may clarify this issue. I shall turn now to a consideration of the factors that enable an infant to develop nutritional independence.
Maternal Time Budgets and Infant Maturation
We have seen that rainfall and group movements affect individuals' time budgets. How does the presence of an infant create additional demands that may restrict a mother's behavioral options and perhaps precipitate the higher mortality found at this period? In this section I shall consider the effects on a mother's time budget of just one variable, but an important one the energetic needs of her infant at various ages. The energetic requirements of pregnancy in humans and other mammals are well documented. With the birth of her infant a mother begins to provide nutrition through milk production, an energetically less efficient system than the plagcental one. As the infant grows, its nutritional requirements increase as energy is required to build new tissue, maintain existing tissue, and support higher activity levels as the infant begins to play, explore, and provide its own transportation. In the discussion of seasonal effects on time budgets I assumed that the differences between seasons in the percentage of time spent feeding result not from weight gain or loss or from changes in energetic requirements but rather from differences in feeding efficiency due to changes in food availability. In the present discussion I shall assume that within a season differences in feeding time result from differences in energetic demands. Although differences in feeding efficiency probably exist as a result of differences in dominance rank, it seems reasonable to assume that these are slight compared with differences caused by pregnancy and lactation.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 19
According to the model, at parturition a female would have to spend another 7 percent of her time (over her own 43 percent maintenance level) feeding just to provide energy for her newborn infant. A female would have to increase her feeding time from the 43 percent of her time spent feeding to maintain only her own body weight to 58-66 percent during month nine of infant life, if she were providing all of her infant's energetic needs and were doing so only through lactation (these percentage incremental values are consistent with those found for humans). She would still need to spend approximately 23 percent of her time walking for a total of 81 to 89 percent of her day occupied just by feeding and walking. However, at these levels she would no longer be able to rest for 17 percent of the day, even if she could totally eliminate time spent socializing. The result is that her overall activity level would in fact be greater, creating even greater energetic requirements for her own maintenance, and she would therefore need to spend even more time foraging.
The conclusion we must reach is that even with fairly conservative estimates of energetic demands, a mother could not provide all caloric requirements for herself and her infant beyond six to eight months of infant age and probably could do so up to that age only with difficulty and major restructuring of other aspects of her life. If the model were modified to incorporate the refinements I have indicated, would the apparent required feeding time be reduce. Most assumptions were conservative and refinements would lead to more intense time budget constraints, especially after the infant's first few months. Perhaps, then, mothers and infants have had to accommodate to these constraints as a reality. Perhaps mothers cannot always maintain their own weight and infants must provide some of their nutrition. If so, infants' maturation and learning and other factors that facilitate the transition to nutritional independence have probably been under considerable selective pressure .If we examine the observed values obtained during this study, it is clear that a female's time budget is affected by the fact that she has a dependent infant and by the age of that infant, but that the effect of infant age is less than that which was predicted above. Mothers are probably not maintaining their body weight. It is known that women who lactate successfully and whose caloric intake during lactation is 23 percent over their normal intake do not maintain their body weight, whereas at 32 percent, women maintain steady body weight. If such weight losses occur in baboons, in sufficient nutrition and weight loss may be a major source of maternal susceptibility to death and may place severe limits on the length and intensity of the lactational period unless females are able to store an appreciable supply of excess fat during pregnancy. Because reduced maternal health would directly affect the chances of survival of the mother's current infant, there will be immediate and evolutionary pressure for factors that enable infants to provide some of their own energetic requirements.
The time course of energetic demands seems to be as follows. During the first two months of infant life the additional amount of food that a mother requires to support a dependent infant over the amount required during pregnancy is primarily due to the lower efficiency of lactation but is also due to the energetic requirements of retrieving and attending to the infant when it is out of contact and to a small amount of infant growth. In the next three months the infant's continued growth and increased activity level place considerable strain on the mother's ability to maintain her own weight because the infant cannot contribute appreciably to its own nutrition at this stage; but also I suspect that mothers lose weight during this period. If milk supplies are reduced owing to maternal nutritional strain and weight loss, infants may have additional "motivation" to eat the many plant foods that they explore.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 20
By the time their infants are five or six months old, mothers are feeding all the time they can (60 percent) without sacrificing a considerable portion of social time and/or rest time. If they sacrifice rest time or time spent being groomed in favor of other activities, they will need to feed even more because any other activity would require more energy than these do. Thus it appears that mothers may have reached a maximum of feeding time by the time their infants are five to six months old, perhaps even with weight loss. It is surely necessary for their infants to provide considerably for some of their own nutritional needs. The infants can more readily do this at five or six 11 months of age if the right foods are available.
Weaning Foods
Recently, anthropologists have emphasized the importance of availability of so-called weaning foods as a major determinant of age of weaning, and consequently of the amount of lactational energetic demand on the mother and of the length of postpartum amenorrhea and interbirth intervals. What is a weaning food? For a human infant, it is a food that is both easily eaten (one that is soft and smooth, like porridge) and readily digested. For a baboon, whose mother neither collects nor prepares its food, the ease of obtaining the food must also rank among the major criteria of a weaning food.
A detailed analysis of feeding behavior and nutrition of weanling baboons in Amboseli is under way, as is a related study of vervet monkeys (Cercopithecus aethiops) in the same habitat. However, the extremes of food accessibilities are quite obvious even to the casual observer. Flowers, particularly those of umbrella trees (Acacia tortilis) and fever trees (A. xanthophloca), are abundant seasonally in Amboseli and easy to pluck. Any infant who can negotiate within the trees (i.e., any infant older than a few months) can readily eat large quantities of these sweet tidbits. In at least some years, umbrella trees flower more heavily than do fever trees. Their branches are more horizontal and have rougher bark, and therefore can be negotiated more readily by infants and at a younger age than can fever trees. Many mature blossoms come loose and fall to the ground as the baboons feed. Thus even Pedro, who could not climb at all and had no fine motor coordination in his hands, was able to eat umbrella tree blossoms, picked from the ground, as virtually his only food other than milk. It may not be coincidental that he lived two months (late December to early March) after his impairment became severe, when we thought that he would die any day. He died at the beginning of March, soon after the period of abundant acacia blossoms was over.
4 Fruits and berries (e.g., Tribulus terrestris, Azima tetracantha, Salvadora persica) and the freshest green grass blades and leaves are , probably the next best weaning foods; however, skill is particularly required to pluck A. tetracantha berries without being stuck by the abundant sharp thorns of this shrub and small infants can only reach the lowest branches. Gum of very small, shrub like fever trees is probably also a good weaning food--it is high in carbohydrates--but to obtain gum from the larger fever trees, such as are used by the baboons as nighttime roosts, requires an ability to negotiate the long, smooth, upright trunks and branches of these trees. The youngest green acacia pods are probably fairly accessible and manageable, but the youngsters apparently need to extract the seeds and discard the pods themselves, although adults (at least the males) eat virtually the whole pod. Consumption of the acacia seeds probably is limited by the presence of toxins, to which the young animals may have a lower tolerance than do adults.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 21
At the other extreme are grass corms, one of the few foods available by the end of the dry season (October), the harvesting and consumption of which account for the largest proportion of the adult baboons' time budget except in January, February, and August (feeding ; on berries and gum occupies almost as much time in December). Even older infants cannot dig anything other than the smallest corms. This is probably the major food that infants scavenge, sorting through the discarded scraps at a place where their mother or a male associate has been digging.
Is there a season when these weaning foods are most available, and is this time fairly circumscribed? For 1974-75, some relevant data are available from Post (1978). (For 1975-76 much comparable data will be available in S. Altmann in preparation and in D. Klein in preparation, but the timing of changes in the tree phenology in particular seems to be fairly invariant from year to year despite annual variations in rainfall patterns.) During 1974-75 over 50 percent of the umbrella trees had blossoms in December and January; about 15 percent in November, February, and March; none in other months. In December, January, and February over 10 percent of the trees had heavy blossom production, more than in any other months. During no month were as many as 10 percent of the fever trees in heavy flowering, but in October and November about 20 percent of the trees had some flowers, and in December about 5 percent. Ripe Azima berries were most abundant in January, and were very accessible in February and March.
Thus available data on plant phenologies indicate that December, January, and perhaps February are the months in which an infant could most readily start taking solid foods. From observations on development of both gross motor coordination for climbing in the trees and fine coordination for manipulating foods, I would estimate that a baboon infant in Amboseli would have to be at least three to four months of age even to begin to utilize much weaning food, and perhaps another two months older before attaining sufficient competence to contribute appreciably to its own nutrition. In the previous section it was also seen that mothers probably find it increasingly difficult to provide infants of this age with all their energetic needs. Infants that are conceived in December and January are born in June and July and would be at the right age to utilize weaning foods when these are most available. Therefore, one would predict the highest survival rates for infants born in June and July. Moreover, because food is apparently also most available to adults in December and January (these being the months during which the least time was spent feeding, during both 1974-75 and 1975-76), it is also reasonable to expect highest conception rates during these months.
Thus both factors suggest selection favoring a birth peak in June and July. I examined the seasonality of conception and the differential survival of infants born at different times of the year. The suggestion that food availability affects baboon reproduction in Amboseli is substantiated by the available data. Of 54 pregnancies for which we know the month of conception, 13, or 24 percent, of the conceptions occurred in the two months December and January, a result in the predicted direction but not statistically significant. However, conception by females with a surviving semi-independent offspring would be expected to be even more subject than other females to the effects of the seasonal availability of food. Of 34 such conceptions, 11, or 32 percent, occurred during December and January, about twice the number one would expect without seasonality.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 22
What of the survival chances of infants born at different times? The infants conceived in December and January also have higher chances of live birth and first-year survival (11/14 = .79) than do infants born at other times of the year (20/36 = .56). (The sample size is slightly smaller for this comparison than for the previous one owing to incomplete survival data for recent births.) Despite the large difference in these two values, sample sizes are not adequate to reach statistical significance.
Given the apparent advantages of seasonality, one might ask why infants are born any time other than June and July, and why mothers conceive any time other than December and January. Such extreme seasonality would entail interbirth intervals of either one year or two. That baboons are capable of one-year intervals is clear from the fact that these are the norm in some zoos (e.g., Lincoln Park, in Chicago); Thelma Rowell (1966b) gave the period of postpartum amenorrhea as five to six months and a subsequent cycling time as one to three cycles in her caged colony in Kampala, Uganda, and perhaps also in the rich riverine habitat of Ishasha, Uganda. Elsewhere, however, in the widely varied habitats of Gombe, Gilgil, and Amboseli, postpartum amenorrhea is of the order of ten to twelve months if an infant survives. A subsequent cycling time of about four to five months, then, does result in almost a two-year interval.
There are two situations in which one would expect "off-season" conceptions and infant survival to be higher than usual. The first is an occasional extended rainy season or other factor that leads to an extension of the season of good weaning foods and of generally higher food availability. When this occurs, females will be more likely to conceive during these off-months and infants who were born at nonoptimal times and are semi-independent when this extended good time occurs will be more likely to survive. Occasional good years may reduce the ecological pressures for birth seasonality. The second situation occurs when a female's previous infant dies. Then the female is faced with a "decision" conceive now or wait perhaps several months or more for the best conception time. If she has no dependent infant she will probably be in better physical condition and therefore more able to conceive and to produce a healthy infant with good survival chances. Also, by doing so she will not be endangering the survival of a present young offspring because she has none. Thus the variability in advantages of conception during different seasons is not as great for these females and they are more likely to have off-season conceptions. Since high infant mortality is characteristic of most nonexpanding populations, it will often tend to reduce seasonality of births in a habitat and species for which factors favoring birth seasonality are not already very strong.
These two situations probably account for the absence in the literature of a clear demonstration of birth seasonality for any baboon population. Kummer (1968) described two birth peaks in the hamadryas baboons but also noted that birth peaks occurred at different times in harems in the same area. More recently, Abegglen (1976) found a late spring birth peak in several bands of hamadryas over a period of several years. In Amboseli, the 1963-64 data and our less complete records on other groups since 1971 all indicate a seasonality similar to that documented here for Alto's Group.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 23
Seasonal variability in rainfall and food availability is reflected in the baboons' daily time budgets, the average distance they travel each day, and in the seasonality of births and infant survival. A model of a mother's feeding time, based on a mother's providing all her infant's nutrition, resulted in a prediction of severe time budget problems for mothers of older infants even at quite slow rates of infant growth. Observed feeding time was below predicted amounts for these mothers. I suggest that the compensating factors are (1) maternal weight loss to compensate for energetic requirements that cannot be met within a tolerable time budget and (2) eventually infants' providing some of their own food.
It is important to note that no category labeled "infant care" was included in mothers' time budgets. For baboon mothers as for human mothers, most infant care is done concurrently with other activities. This is true even when the infant is not in contact; mothers are probably "tuned" to their infants, alert to possible trouble. We do not yet know how infants affect mothers' abilities to attend to other stimuli or how efficiency of other activities is affected by concurrent infant care for any primate. It seems likely that the efficiency of activities such as feeding is lower than it would otherwise be for females when they have infants and that this might result in further strain on mothers.
Reproductive success and survival of Amboseli mothers and infants were seen to be subject to considerable environmental influences. It is not unreasonable to expect that their behavior and physiology have been molded through natural selection to respond to these conditions and that they also respond facultatively (flexibly) to make the best use of alternatives in the particular situations in which they find themselves at any given time.
In the next chapters I shall consider social and other behavioral interactions, between mothers and infants and between each of them and other group members; the developmental course of these interactions; the meshing of these behaviors with the less social aspects of their world that have been considered thus far; and the extent to which they relieve or intensify pressures on mothers and infants.
Social Milieu
JUST AS THE MONTH of birth and other aspects of seasonality may result in individual differences in the ecological pressures on mothers, so may individual differences in social experiences affect the mother and her infant, both directly and indirectly through effects on the mother. What are these social experiences? How do they affect mothers' time budgets and create attentional demands, and in what other ways do they appear to improve or to reduce maternal and infant survival? An understanding of the sources of these differences is the first step toward determining potential lifetime and intergenerational continuity in such experiences. At parturition the social life of a baboon female changes dramatically. She must not only nurse, carry, and protect the neonate while still providing her own food, transport, and protection, as before; but in addition, she and her infant become a major focus of interest within the group, a common characteristic of primates.
Several field studies have resulted in qualitative or normative descriptions of the social world of savannah baboon mothers and their infants: those of DeVore (1963) and Rowell and Ransom (Ransom and Ransom 1971, Ransom and Rowell 1972), all for olive baboons, Papio anubis. In addition, some quantitative data are provided by Nash (1978) primarily for 6-to 18-month-old anubis baboons and their mothers. Cheney (1978) and Seyfarth (1976) present some relevant quantitative data from a general field study on a small group of chacma baboons, P. ursinus. Rowell et al. (1968) studied mothers and infants in a small captive colony of anubis baboons.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 24
Most general descriptions of the social relations of baboon mothers are consistent across studies. In particular, all authors report that mothers of young infants receive little overt aggression, more grooming, and more approaches than do females in other reproductive stages. This general pattern of interactions within a group has also been described from field and laboratory studies of most other primates and probably comes closer than any other to being a primate "universal." One might be tempted to assume that the social group provides support for and reduction of the stress of motherhood. However, as I discuss below, a baboon mother's social world may not be as benign as these descriptions imply, and occasional extreme violence toward primate mothers or infants provides rare but chilling exceptions in some species.
The social group has an impact in both active and passive ways. The active ways are fairly obvious: individuals groom each other, play, fight, and so on. Most of the time, however, individuals, even close neighbors, are not interacting. But the mere presence of conspecifics can have a social effect even when these animals are not engaging in a social interaction. The presence of individuals who are alert to danger or who locate possible food sources may be beneficial to nearby group members. Spatial arrangements within groups also provide the broad outlines for social opportunities that may be used or not--a large adult male, just by his presence, may discourage others from approaching a mother; the mere presence of an individual who has harmed a mother previously may disrupt her activities or result in her restricting her young infant's movements. Thus consistent spatial patterning can be a clue to rarely observed interactions. In the sections that follow, before analyzing the more obviously beneficial or harmful interactions, I shall first examine the spatial patterning, that is, neighbor relationships. Then I shall turn to approaches: the interface between the statics of spatial relationships and the dynamics of interaction. Finally, I shall examine two major forms of social interactions, apparently beneficial social grooming and stressful agonistic interactions, including spatial displacements, or supplantations.
Sleeping Grove Subgroups
Most of our observations of baboons are made during the daytime. At night the animals are high in the sleeping trees. Their location and the lack of available light make observations most difficult. Fortunately for us, it appears that little activity usually goes on at night; this is suggested by two all-night watches that we have made and by the fact that individual animals can usually be relocated in the morning in the same place that they were seen to settle into the night before. Yet spatial relationships at night may be quite important. Early-morning grooming sessions often occur in the trees between individuals who sleep near each other. Also, predation seems to occur primarily at night, a fact that perhaps renders nighttime spatial relationships particularly important; for example, smaller animals may be less subject to predation if they sleep next to an adult male. Then, too, close neighbors may provide each other with warmth during the cool, dry savannah nights. Finally, the nighttime relationships, by their static nature, may elucidate patterns that exist during the day but are overlaid with foraging and with general activity levels that produce a more fluid social world. Therefore, it seems appropriate to consider first the sleeping grove subgroupings that constitute the spatial milieu during 13 to 14 hours each day.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 25
During 1975-76, although Alto's Group used 15 to 20 groves of trees that were scattered throughout the group's home range, one was used most often, over 40 percent of the time. This "Favorite Grove," as we dubbed it, consisted of two trees with continuous crown, and a third tree that was sufficiently separate that animals moving from one subgrove to the other went down one trunk and up the other rather than attempt the long jump across the branches.
It appeared that the same individuals consistently used each of these two parts of the grove: in fact, individuals were very consistent in where and near whom they slept even within their respective trees. Although I could not keep consistent records of the latter, I did record which tree subgroup each group member was in whenever the group slept in Favorite Grove and members were still settled in their sleeping postures when I arrived in the morning. All members were so located and identified on each such sample day unless, as occasionally happened, descent occurred too rapidly or too soon after my arrival. This sampling was begun in February 1976, when I could identify with confidence all individuals in virtually any position while they were huddled high in the tree, something that I could not do in the early months. I have data for 44 days that the group used Favorite Grove, from February through July and in October. For those baboons who neither died nor migrated during this period I have data from about 35 to 40 days in which subgrouping occurred (none occurred on 2 nights).
Ad libitum observations of spatial patterning in other sleeping groves were consistent with those in Favorite Grove, especially at the level of the three or four closest animals in small subgroups. However, comparable quantitative data could not be gathered for these groves owing to a lack of clear physical division within the groves, infrequency of grove use, or poorer visibility within some of the groves.
The subgroup data yield information about the affiliative patterns within age classes and the maturational trends in relationships of mothers, infants, maternal siblings, and cohorts.
Almost all individuals were at least 90 percent consistent (no more than 4 switches out of 40 samples) in their subgrove choice, most of them making no switches at all despite births of infants and other changes in reproductive state. Of the fully adult baboons, only male High Tail with 5 switches in 13 samples taken before his death and female Plum with 12 switches in 33 were less consistent. Adults consistently in the left subgroup were males Slim and Peter and females Alto, Spot, Vee, Preg, Scar, Oval, and Judy. Consistently in the right subgroup were females Mom, Lulu, Fem, Gin, Slinky, Handle, Este, and Brush and males Even, Ben, and Max.
Of the young adult males, Russ and Stu gradually made the transition from one subgrove in February to the other by October, moving in opposite directions. Among the older juveniles and subadults, Toto made 7 switches in 37 samples. The two- to three-year-olds tended to sleep in the same subgrove as their mothers but not uniformly.
All animals less than two years old slept in the same subgrove as their mothers except Pooh, who had severe locomotor impairment. She slept with or near adult Max in the rightmost tree, which she could climb more easily than the others. Fred slept with his mother; Alice did so until Alto's death, at which time Alice began to sleep with adult male Peter or her sister Dotty (Alice was 17 months old at the time). Ozzie slept with his mother, Oval, until the latter part of Oval's next pregnancy, when she overtly rejected him; he was then about 18 to 19 months of age. After that he sometimes slept with his older sister, Fanny.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 26
Several factors probably led to the average relatedness within sleeping subgroups being higher than the relatedness in the group as a whole. As noted above, both infants and their next older siblings tended to sleep in the same subgroup as their mothers. Moreover, the adult males and females of a subgroup tended to be each other's preferred mating partners. Therefore, the fathers of a subgroup's infants were likely to be the males of that subgroup. Finally, all adult females (with the partial exception of Plum) who had been members of High Tail's Group before the merger, were in the same (right) sleeping sub group. As we shall see below, a mother's sleeping subgroup tended to include the individuals who were her daytime neighbors and interactants.
Daytime Neighbors
During the daylight hours, the baboons spend most of their time foraging on the ground, where they move more easily than in the trees, sometimes gather in clusters, and are not restricted by particular comfortable locations, as they seem to be in the trees. Infants can more readily move about and do so at a younger age. In the daytime I studied neighbor relationships in finer detail. Note that when I examine the identities of mothers' neighbors and interactants, I usually focus only on the infant's first three months of life rather than older ages. This is done for two reasons: because the mother's and infant's worlds most completely overlap during these months and because, as can be seen below, these are the months of greatest social involvement. These are also the only months during which baboon infants possess their distinctive black natal coat. Coat change begins during month three and is mostly complete by the end of month six.
Two aspects of neighbor relations may be of considerable importance to mothers and infants: the density of neighbors and the identity of these neighbors. From W. D. Hamilton's work on adaptive group geometry (1971 ) and W. C. Allee's early studies of the advantages of sociality (1931), one would predict that being surrounded by more conspecifics for more of the time would be advantageous to an individual in that it would provide additional protection against predators. This would be even more true if, as is sometimes the case in baboons, this circle includes at least one adult male: the large canine teeth of adult male baboons are formidable weapons. Alternatively, other arguments emphasize the potential disadvantages of being close to conspecifics, in particular the increased likelihood of disease transmission and of feeding competition. I shall consider the relevance of each of these suggestions in the context of the neighbor patterns found in this study.
The point-sample data allow estimation of the percentage of time that animals spend in proximity to each other. I recorded the identities of all individuals who were within 2 meters of the focal female, a distance chosen because it seemed to represent an individual's "personal space": there were few animals that an individual would tolerate that close to it for long. Neighbor data for greater distances were also gathered but will not be discussed further here.
Only rarely did baboons spend 10 percent or more of their time within 2 meters of new mother. In almost every such case the individuals near a mother were either family members, one or two adult males, or another mother with a same-aged infant. Five percent of the time spent in proximity, defined as within 2 meters, was about the lowest level that I could reasonably expect to measure when partitioning each female's point-sample data by months. For each female and each month of infant life, all individuals who spent at least 5 per cent of the time nearby were considered.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 27
The sharp increase in neighbor density during month one of infant life (i.e., between birth and one month of age) over that seen during pregnancy, some increase again in month two, and a consistent decrease after month two, dropping to late pregnancy levels by about month seven to nine. Note that the average number of neighbors per sample increases by approximately the amount that we would expect from the increase in the amount of time that there is at least one neighbor within 2 meters. That is, new mothers are "alone" about half as often as when they were pregnant; however, when there is at least one animal nearby, the number of neighbors is approximately two during pregnancy and at each infant age. We do not yet know the extent of protection against predation that is afforded by this pattern of neighbor spacing, but some degree of protection seems reasonable. This type of increase--neighbors increased time with at least one neighbor but not high densities of neighbors--probably does not result in appreciable increases in feeding competition.
The opportunities for disease transmission may well be greater than during pregnancy because they probably depend not only on the time spent with others nearby, but on the number of different animals to whom a mother and infant are exposed. During the last month of pregnancy, females averaged three or four different individuals who were their frequent neighbors. Although after parturition the set of frequent neighbors still represented a small fraction of the total group membership of about 45 animals, for all of the females the number of different neighbors was greater during the first month of infant life than during the previous month, for an average of eight different individuals who spent more than 5 percent of the time nearby. Nine individuals spent at least 5 percent of the time nearby during month two, six or seven in month three, five in month four. Thus, many more different individuals were spending at least 5 percent of the time near new mothers than had done so near pregnant females, probably increasing the likelihood of disease transmission.
Both feeding competition and likelihood of disease transmission may also depend on variability in the tendency of particular individuals to engage in harmful or helpful activities when they are nearby. Some individuals may provide more assistance or threat than others, both immediately and as potential long-term associates. Who were the individuals who were frequent neighbors?
The tendency of particular adult males to associate with particular mothers is clear. For example, both Brush and Mom with Moshi had two adult males who spent time nearby, but it was Ben and Max for Brush, Peter and Slim for Mom. After an infant was about two months of age, some associated adult males also spent time with the infant when it was separated from its. Male associates were members of the mother's sleeping subgroup and usually had previous associations with the mother, sometimes including mating when the infant was conceived. Their interactions will be examined in more detail in later sections.
Although four- to six-year-olds interacted with active, especially semi-independent, infants, they rarely spent much time near the mothers. During the year of this study, all members of this age class were males (Dogo, Nog, Toto, and Swat). Females of this age class are approaching menarche and their first year of cycling. Their interactions with mothers and infants might be quite different and are now under study in Amboseli.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 28
The two- to three-year-old juveniles varied considerably in the time they spent with new mothers, even with their own mothers when they had infants. Females Cete and Nazu were only a year and-a-half old when their mothers gave birth to Summer and Pedro; it was during those pregnancies that these young juveniles were probably weaned. They did not stay near their mothers during the first months after Summer and Pedro were born and only later interacted with their siblings. The same was true for male Ozzie and female Pooh when their mothers' next infants were born. Females Janet, Striper, and Fanny, by contrast, were two- to three-year-olds when their current siblings were born, and each of their mothers had experienced at least one other pregnancy since their births. They all showed considerable interest in their siblings, as did two-and-a-half-year-old female Dotty when her sister Spot gave birth.
With family data excluded, there are still clear overall differences among these juveniles. Janet, Nazu, Fanny, and Striper were common neighbors of mothers: each of these juveniles was included in one fourth to one-third of the data for mothers with infants in the first three months. In contrast, Dotty, Cete, and male Jake appeared in less than one-tenth of the data. Thus most juveniles who tended to be interested in infants to whom they were related were interested in most unrelated infants as well. Neither age nor dominance rank explains the differences among the juveniles. Follow-up studies of these juveniles and of the later cohorts are under way. The yearlings spent much less time near new mothers than did the two- to three-year-olds, and the time they did spend was usually spent in conjunction with their own mothers. Often a weanling would get on its mother's nipple while its mother groomed a new mother. Female Alice, offspring of the highest-ranking female, was an exception: she was highly interactive in general and spent time with new mothers, often sitting in their ventrums and pushing aside these mothers' infants. She spent much time near Judy, Vee, and her sister Spot. Male Ozzie also spent considerable time with Spot and Vee but not with his mother, Oval, when she had a young infant. Female Eno and male Fred often were near Gin. Female Pooh was virtually noninteractive and spent little or no time with any of the new mothers, including her own when Peach was born.
No general patterns emerged from an analysis of adult female neighbors of mothers except that Gin and Mom were particularly likely to be neighbors of other mothers during the first month of life of the other mothers' infants. Some pairs of females who gave birth within a week spent much time near each other (Spot and Judy, Gin and Slinky); others did not (Mom and Brush, Vee and Plum). But even for those pairs that spent time near each other, the maintenance of the spatial relationship was often quite one-sided, as is shown in a later section. Moreover, some individuals who spent time together interacted seldom, and some frequent interactants did not spend much time together.
It is also clear that mothers varied considerably in the number of frequent neighbors they had, particularly during the first two months. Gin, Vee, Spot, and Scar had the most neighbors; Brush, Handle, Plum, Judy, and Mom with Moshi (but not with Misty) the fewest. In general, the former group is composed of females who are younger, rank higher, and have female infants, but it is not clear what variables determine variability in neighbor densities for neonates and their mothers. Females whose infants were born at about the same time varied--Vee with many neighbors and Plum with few, Spot with many and Judy with few, Gin with more than Slinky, Scar with more than Preg, Mom (with Misty) with more than Brush. Looking at these matched pairs does not clarify the picture. The direction is consistent with rank for four of five of these pairs, with age for four of five, and with infant gender for three of four (Plum and Vee both had female infants). Mom would be considered old and high-ranking when she had each of her infants. She had more close neighbors with her female infant, Misty, than with her male infant, Moshi.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 29
Whatever the cause, some infants more than others grow up in frequent, close proximity to many individuals. This may speed their social maturation. It may also increase their exposure to disease and increase the amount of feeding competition that their mothers encounter, but there was no clear relationship between number of frequent neighbors and disease or mortality in this study.
In summary, mothers spent more time than others in close company with at least one other animal, and more individuals spent time near new mothers than near females without infants or mothers with older infants. Particular members of each age-sex class tended to spend time near mothers and infants. Some individuals, particularly adult males, spent considerable time with some mothers, and no time with others. Some mother-infant dyads had many individuals frequently in close proximity; others had few. Kin relatedness was not a major predictor of observed individual differences.
I have suggested some implications of the results for feeding competition, disease transmission, and predator protection. To further evaluate neighbors' potential effects, it is necessary to examine the nature of the interactions that occur among individuals. I shall turn now to some of the dynamics of relationships, first the tendency of individuals to seek each other out, that is, to approach each other, and then agonistic and grooming relationships.
Approaches
Social bonds are often measured by considering only active behaviors, such as grooming or sexual mounting for evaluating positive bonds, or aggressive encounters for evaluating repulsive relationships. Yet it seems reasonable that calm acceptance and shared proximity are also important. Such relationships, if they exist, contribute to the spatial patterns seen and described above, and provide the physical availability of animals for more active behaviors such as grooming, play, infant carrying, and perhaps even fighting; but it seems likely that they more often represent positive or helpful relationships than antagonistic ones. Therefore, I shall first consider close approaches, accompanied by no other social behavior and response, that is, those that result in the two animals just sitting or standing in proximity. Then in the next section I examine approaches that are part of a sequence of social interaction. Spatial displacements, or supplantations, where it is the place rather than the individual that is approached, are considered separately in the section on agonistic interactions.
SIMPLE, OR NONINTERACTIVE, APPROACHES
For practical reasons, approaches by one individual to another usually can only be identified, in the absence of a response by the second individual, when the approacher comes within a few meters of its object. I recorded as simple, or noninteractive, approaches all those approaches that carried the actor at least 1 meter (approximately a body length) and that brought the actor to within 2 meters of the animal being approached. These could be reliably scored without response by the object animal. As noted above, 2 meters seemed to represent an animal's personal space. Thus I wanted to determine which animals would be approached that closely with no further interaction, and which animals' approaches to such proximity would be tolerated by an animal who was approached. With which animals do such calm approaches occur? Are they more common or less after parturition?
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Baboon Mothers and Infants by Jeanne Altman excerpts part 30
For all 13 females the average rate of approaches to them was greater than the approaches by them. Each mother had a small set of individuals whom she approached, and this was to a considerable extent a subset of those from whom she tolerated approaches. In particular, most mothers had one adult male with whom they shared these approaches, for example, Mom-Moshi with Slim, and Brush with Ben.
There were usually more individuals who approached mothers than the mothers themselves approached. From the last month of pregnancy to the first month of infant life, both of these total rates (to and by the mother) rose slightly. The amount of the rise was small, but the change in direction was consistent: it increased for seven of nine females in the approaches by them and nine of nine for the approaches to them. In some sense, then, one might say that the time of birth was a time of drawing together of individuals who were relaxed with each other, and that this is one of several dynamics that caused the increase in neighbors described previously. For later months of infant life the rate of noninteractive approaches varied little from month to month, and it was inconsistent in direction of change from individual to individual and month to month. Unlike the rate of interactive approaches I shall consider next, the rate of noninteractive approaches does not reflect developmental changes in mother-infant contact or other aspects of infant maturation.
In examining differences among mothers it is necessary to consider that rates of noninteractive approaches both to and by mothers were probably underestimated, and equally so, in the first few months of this study. Thus to compare the rates for various females I did not include data before late September. Considering the remaining data, I found no pattern in the rate at which various mothers made noninteractive approaches to others. In the simple approaches made to mothers, the three highest-ranking (Vee, Spot, Mom with Moshi) had the highest rates (but Mom with Misty had the lowest). Among the juveniles only Dotty consistently made noninteractive approaches to several different mothers. The lack of a very clear-cut pattern may be due to the overall low rates of these behaviors.
Except perhaps during the first month of infant life, the rate of these calm approaches probably contributes to, but is not sufficient to account for, the appreciable increases that we found in the number of neighbors; but it is unlikely that the rate itself has an appreciable influence on mothers and infants. What is probably more important is the actor-recipient selectivity of these acts: mothers are brought closer to particular adult males and in some cases to other females with like aged infants. Those cases for which we have both likely paternity and behavioral data during the infant's first months indicate that the adult males involved are likely to be the infant's father. The adult female associates are not likely to be closely related through maternal lineages, but rather share common needs and experiences, and their infants provide each other with play mates. Actually, mothers of like-aged infants, or the infants themselves, may be more closely related than we suppose from a consideration of only maternal genealogies. Females who are closely associated tend to associate with the same one or two males. Thus their infants are likely to be paternal siblings. If, in addition, these mothers are of the same age cohort and formed their association in infancy, they, too, may be paternal siblings. At this stage of our knowledge, however, these suggestions are purely speculative.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 31
INTERACTIVE APPROACHES
A much more common class of approaches consists of approaches that were accompanied by other social behaviors or that were followed by some detectable reaction on the part of the animal being approached. These interactive approaches were followed by sequences of behavior ranging from relatively long energetic ones, such as fights or other dominance interactions, handling and pulling of associated infants, and grooming, to brief lipsmacking, body aversion, or a slight touch. Most social interactions, both beneficial and harmful ones, begin with an approach. Spatial displacements, which involve approach to another animal's location rather than to the animal itself, are considered separately in the agonistic section below.
In general, mothers initiated interactive approaches slightly more often than they did the simple, or noninteractive, approaches, and did so at a rate that increased very slightly with the birth of their infants and then changed little with the maturation of the infants. This is in striking contrast to the rate of interactive approaches directed toward mothers, which soared with the birth of their infants and then steadily decreased in the subsequent months. In their infants' first few months of life, mothers were all the recipients of interactive approaches much more often than they were the actors; later the differences were small and reversed in direction for some females and for some months. The six- to eightfold increase in approaches after the birth of an infant is much greater than would be expected from the fact that two individuals (mother plus infant) are now being approached rather than just one, as before.
As an infant matures, its mother may be approached less often because the infant spends less time in contact with her, enabling others to approach the infant at times other than those when it is with its mother. The relationship between infant contact and approach rate can be examined at the level of the immediate behavior by determining whether at any given infant age a mother receives more interactive approaches when her infant is actually in contact with her than the expected number of interactive approaches, calculated from the proportion of time the infant spends in contact that month multiplied by the total number of interactive approaches to the mother that month. Using CRESCAT to perform sequential pattern searches, I determined whether the infant was in contact or not when an interactive approach occurred by identifying each change in mother-infant spatial relationships and then labeling each occurrence of a social behavior, including interactive approaches, according to whether the mother and infant were in contact at the time the act was performed.
When their infants were in contact, mothers received more interactive approaches than expected in 59 of 72 mother-months (plus 13 ties). Results of (binomial) significance tests are a function of probability (contact time) and N (total number of approaches) for any month, which vary considerably in this case. Although the magnitude of the difference between observed and expected values was sufficient to reach the .05 level of significance for only about half (34) of these positive-deviation months (and two of those with negative deviation), the probability of 59 of 72 results being in the same direction by chance is extremely low (P <.001). Moreover, if data from all females for each month are pooled, mothers were approached significantly more often when their infants were in contact during all but months one and twelve.
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Baboon Mothers and Infants by Jeanne Altman excerpts part 32
Interest in the mother-infant pair may also wane if older infants are less attractive to others than are younger ones. To examine this possibility I looked at the rate of approaches to a mother when her infant was in contact. For four females data were available for the last month of pregnancy as well as for all of the first six months of infant life (but not necessarily for later months). For each mother I calculated the rate at which she received interactive approaches during the last month of pregnancy, which I considered her "base rate," the rate at which she would receive such approaches if she did not have an infant. Then, if a female's "attractiveness" was independent of her status as a mother and the presence of her infant, we would expect that she would receive that same base rate of interactions while her infant was in contact (or, at most, twice the base rate if one considers that two individuals are being approached) and that this rate would be independent of the age of her infant. After the base rate for each mother was subtracted from her rate for each month thereafter. They demonstrate that a female received approximately six times as many interactive approaches after parturition when her infant was in contact, and that the rate of approaches was independent of infant age until the infant was four or five months old. However, the rate dropped dramatically in the sixth month. It is interesting to note that at about month six infants have lost most of their distinctive black natal coat. The present results are consistent with the suggestion that infants who have lost their neonatal coat may be less attractive to other group members. However, the decrease in approaches to mothers of older infants may be produced by other factors. For example, infants may remain attractive but others may selectively approach them when the infants are not in contact with their mothers. I shall also examine the contingencies between infant contact and maternal activities at certain infant ages, and consider the relationship of those contingencies to alternative explanations for the remaining age effects found in approach rates.
Who were the individuals who approached and interacted with mothers, or whom the mothers themselves approached? For interactions with adult females the pattern was somewhat different from that for interactions with males. A few females seemed to exhibit interest in many infants, others