Glenn Hausfater

Life History of Yellow Baboons: Physical Development, Reproductive Parameters, and Infant Mortality

Longitudinal data from a population of yellow baboons,Papio cynocephalus, in the Amboseli National Park, Kenya, provide life history parameter estimates. Females reached menarche at approximately four-and-a-half years of age and then cycled for approximately a year before first conception. Postpartum anestrum averaged 12 months but ranged from six to 16 months. In cases of still births or infant death during postpartum amenorrhea, females commenced cycling after approximately one month. In mature females the time spent cycling before conception was five months on the average with a range from one to over 18 months. Only half of all full-term pregnancies resulted in infants who survived the first year of life; only a third, in infants who survived until the birth of their mother’s next infant. In comparison with data from laboratory colonies, our data indicate that female baboons in Amboseli are older at birth of first infant. They have, on the average, a somewhat shorter interbirth interval than was estimated from earlier crossectional field data, and therefore spend a larger portion of their adult life pregnant, but have a much longer interval—at least three years on the average—between the birth of an infant and the birth of that infant’s next older surviving sibling. A number of morphological changes in immature baboons are described.

Long-Term Consistency of Dominance Relations Among Female Baboons (Papio cynocephalus).

At maturity, female baboons in the Amboseli National Park of Kenya generally attain a rank position among adults near to that of their mothers. However, the age of a females mother and the difference in ages between sisters also influence the rank acquisition process. These latter demographic variables, which are sensitive to changes in resource availability, may account for the close association both within and among primate species of specific patterns of rank organization and specific environmental conditions.

PREDATORY BEHAVIOR OF YELLOW BABOONS

1. A group of 32 yellow baboons (Papio cynocephalus) in the Masai-Amboseli National Park, Kenya, caught and ate 45 vertebrate prey items during 2519.19 hours of observation. 2. Eighty percent of the prey items were mammals and the most frequently eaten species were African hares (Lepus capensis), vervet monkeys (Cercopithecus aethiops) and neonate gazelle (Cazella granti and G. thomsoni) in that order. The details of predatory behavior for each prey species are described. 3. Rates of predation were significantly higher during the long dry season than during other months of the year, although no correlation was found between total monthly rainfall and monthly rates of predation. A lognormal model however provided a good fit to the monthly rate of predation data suggesting that the rate of predation by Amboseli baboons was affected by several factors that acted multiplicatively with respect to each other and were themselves related to rainfall or dryness. 4. A mean of 2.3 individuals fed directly from the carcass of each prey item. A mean of 3.5 individuals per prey item fed directly or indirectly, i.e., on scraps, from each carcass. In general, both the number of individuals who fed from each carcass and the duration of their feeding bouts was dependent upon the gross body size of the prey item. Adult males fed directly from the carcass of prey items for about three times more minutes than expected from their number in the group; other classes of individuals fed directly from prey carcasses for only one-fourth as many minutes as expected. In general, an adult male would be expected to feed on each category of vertebrate prey at least once per year, while individuals of all other age-sex classes would be expected to feed on most prey categories only once every two years. 5. The most frequent social behavior around prey items was agonistic bouts; no cooperation, simultaneous feeding or specific begging gestures were observed. 6. Estimates of the total number of prey killed annually by Amboseli baboons indicate that baboon predation probably has a negligible effect on prey populations other than vervet monkeys. 7. It is speculated that the need for vitamin B12 underlies baboon predatory behavior, and perhaps that of other primate species as well.

The Reproductive Consequences of Infanticide in Langurs: A Mathematical Model

Summary1.An analysis of the factors influencing the reproductive success of infanticidal and noninfanticidal adult males in populations of langur monkeys (Genus Presbytis) is presented. Male tenure, defined as an adult males length of residency in a one-male bisexual group, is demonstrated to be an important factor in any reproductive advantage accruing to infanticidal males. Other factors include the lengths of the female interconception intervals, the time at which adult male replacement occurs relative to the start of any such interval, and whether or not the subsequent replacement male is also infanticidal.2.Infanticide is found always to confer a reproductive advantage on the resident male in a bisexual group under conditions of subsequent replacement by a noninfanticidal male. Infanticide would thus be expected to spread when introduced into an otherwise noninfanticidal population. Under conditions of subsequent replacement by an infanticidal male, infanticide is found to be advantageous for the resident male only a particular lengths of tenure. Infanticide would thus become fixed only in populations where the distribution of tenure lengths is advantageous for infanticidal males. Accordingly, it is predicted that average or modal tenure length in populations fixed for infanticide should coincide with those tenure lengths theoretically yielding a reproductive advantage for infanticidal males. Three direct estimates of average male tenure obtained from field studies of langur populations are consistent with the predictions of the model.

Posture, Microclimate, and Thermoregulation in Yellow Baboons

This report describes thermoregulatory behavior of free-ranging yellow baboons (Papio cynocephalus) in Amboseli, Kenya. While resting in trees during early morning hours, baboons are directly exposed to thermal effects of wind and sun. We hypothesized that these animals would respond to microclimatic changes by altering their posture and body orientatio so as to minimize thermal stress. The results of this study indicate that air temperature, solar radiation, and wind velocity interact in their effect on behavior as predicted by this hypothesis. Specifically, the most salient cue for trunk orientation choice is wind direction, while posture is primarily influenced by air temperature. In sum, our results clearly demonstrate that when baboons are unable to minimize thermal stress by selecting a more favorable microenvironment, they do so by altering their posture.

Infanticide as an alternative male reproductive strategy in langurs: A mathematical model

Abstract This paper makes explicit some of the assumptions underlying the view that infanticide is one of two (or more) alternative reproductive strategies utilized by adult male langur monkeys (genus Presbytis ). A mathematical model has been developed from these assumptions, and formulae derived which give the equilibrium proportion of infanticidal males expected in langur populations under any given set of reproductive and demographic conditions. Together with estimates of adult male reproductive success obtained from a previous analysis of langur infanticide, these formulae were then used to calculate the precise proportion of infanticidal males expected in natural populations of langurs characterized by specific average male tenures. Further, the number of generations required for such populations to reach their predicted equilibrium was estimated using a simple computer model of langur population dynamics. The present work has thus produced several quantitative predictions which are directly falsifiable with observational data obtainable from wild populations of langur monkeys. With only slight modification, the present model may also be applied to the numerous other primate and non-primate species whose mating systems include many of the same general features as that of langurs.

A note on the activities of a solitary male baboon

This paper describes the behavior and activity patterns of a solitary adult male yellow baboon (Papio cynocephalus) living in the Amboseli National Park, Kenya. Social events surrounding the males departure from his group, his contacts with other baboons while solitary, and events surrounding his return to the group are described in detail. The distribution of the males time among several activity states, called histime budget, the average duration of these activities and the autocorrelation of activity states are analyzed and compared to the same measures of activity taken on group living males. The information presented indicates that a solitary male, even when injured, is not necessarily destined to die or to have a low reproductive potential.

The Functional Significance of Baboon Grooming Behaviora

Grooming is a widespread behavior among primates that is often considered an altruistic or cooperative activity. Since grooming has several functions, ranging from skin care and ectoparasite removal to social communication, there have been many selective pressures on this behavior. Previous studies of primate grooming relations have quantified only a few of the parameters necessary for testing sociobiological hypotheses concerning the distribution of grooming. During 1980-81, an 11-month study of grooming behavior in a group of 45 yellow baboons (Papio cynocephalus) was carried out in Amboseli National Park, Kenya. The baboons were individually identifiable, matrilineal relationships were known, and paternal sibships could be reasonably estimated. The amount of grooming between individuals was measured by group scan samples every 30 minutes, and 20 15-minute focal animal samples per day. The focal animals were 12 adult females of different dominance ranks, ages, and kin network complexities. To determine the major ecological costs and benefits of grooming for this study population, seasonal grooming patterns and ectoparasite-host relations were examined. The time the baboons spent allogrooming decreased slightly as the time spent feeding increased, but the correlation was not significant (Pearsons r = 0.538, p > 0.1) suggesting that the cost of grooming with respect to lost feeding time is small. The rate that baboons encounter certain ectoparasites was estimated by weekly samples of ixodid ticks from the habitat using drag methods and carbon dioxide tick traps. Tick populations varied seasonally with respect to rainfall, but changes in tick densities had little effect on the amount of grooming or on the rate of grooming hand or mouth movements. nVo evolutionary theories, kin selection and reciprocal altruism, were considered with respect to grooming partner preferences by using this data base. As predicted by kin selection, grooming bouts occurred frequently between closely related individuals and less often between nonkin. In contrast, there was little support for the reciprocal altruism prediction that preferred grooming partners should be ones likely to reciprocate. As shown in TABLE 1, there was substantial asymmetry in the number of bouts

Tail Carriage in Baboons (Papio cynocephalus): Relationship to Dominance Rank and Age

Several metric and categorical variables were used to assess tail carriage in 717 photographs of 54 yellow baboons (Papio cynocephalus) of known identity, sex, dominance rank, and estimated or known age. Analyses of these data demonstrated that age was the primary factor, influencing tail carriage of baboons not engaged in social interaction. Specifically, the proximal segment of the tail was carried increasingly close to the vertical with increasing age; other changes in tail angles and segment curvature were also correlated with age. There was no relationship between dominance rank and neutral tail carriage in adult male or female baboons, nor was the neutral tail carriage of the first-ranking male or female either distinctive or characteristic. The morphological basis of ontogenetic changes in neutral tail carriage in baboons is also discussed.