Shirley C. Strum

Habitat use and resource availability in baboons

The behavioural responses of free-living baboons (Papio) to temporal and spatial variation in resources is examined. Group foraging effort was related to per caput food availability, both within the study group (P. anubis) and across a sample of populations. Group size was positively correlated with both home range size and day range length, indicating ecological costs not predicted by a food defence hypothesis of group living. Furthermore, the tendency for day range length of the study group to increase as resources became scarcer was mirrored by inter-population variation; day range length was correlated negatively with mean annual rainfall, once the positive influence of group size had been partialled out. These relationships, which imply a time minimizing rather than an energy maximizing strategy, may be best explained by increased patchiness of food at lower resource densites, rather than lower average biomass within patches. The study group responded to the inferred decrease in the marginal value of patches in the dry season by increasing patch residency times. Multiple regression analysis of total time spent in each quadrat revealed that apparent preferences for particular vegetation zones were a result of the spatial coincidence of these zones with sleeping sites and waterholes, emphasizing the importance of controlling for confounding factors in studying the determinants of habitat selection. In addition, the mean duration of bouts in each quadrat was related to distance to the nearest waterhole, reflecting the constraints imposed by thermoregulatory water loss in a hot, dry environment. Seasonal shifts in habitat selection tracked spatio-temporal variation in the availability of food and water.

Dominance rank, resource availability, and reproductive maturation in female savanna baboons

SummaryTen years of data collected from a population of savanna baboons, Papio cynocephalus anubis, residing near Gilgil, Kenya were analyzed to ascertain the extent to which social and ecological factors influence reproductive maturation in females. First sexual swelling occurred at an average age of 4.79 years and first birth occurred at an average age of 6.92 years. Age at first menses was significantly correlated with age at first sexual swelling, but age at first sexual swelling was not a good predictor of age at first birth. The amount of rainfall in the 6 months preceding first sexual swelling and resource availability were significantly correlated with age at first sexual swelling. When ecological factors were taken into account, dominant females had an earlier age at onset of puberty, but not an earlier age at first birth, than did subordinate females. We suggest that nutritional and social stress operate at the same physiological level to disrupt GnRH pulsatility and retard reproductive maturation in some females. Given that socioecological variables modify the timing of life history events related to fitness in female baboons, the task for the future is to unravel how socioecological factors influence different life history components and generate variation in lifetime reproductive success.

The Development of Primate Raiding: Implications for Management and Conservation

Ecosystems and habitats are fast becoming human dominated, which means that more species, including primates, are compelled to exploit new human resources to survive and compete. Primate “pests” pose major management and conservation challenges. I here present the results from a unique opportunity to document how well-known individuals and groups respond to the new opportunity to feed on human foods. Data are from a long-term study of a single population in Kenya at Kekopey, near Gilgil, Kenya. Some of the naïve research baboons became raiders while others did not. I compare diet, activity budgets, and home range use of raiders and nonraiders both simultaneously, after the incursion of agriculture, and historically compared to the period before agriculture appeared. I present measures of the relative benefits (female reproduction) and costs (injuries, mortality, and survivorship) of incorporating human food into the diet and discuss why the baboons raid and their variations in raiding tendencies. Guarding and chasing are evaluated as control techniques. I also suggest conflict mitigation strategies by identifying the most likely options in different contexts. I end with a proposal for a rapid field assessment of human wildlife conflict involving primates.

Priority of access and grooming patterns of females in a large and a small group of olive baboons

The theoretical basis of Seyfarths priority of access model of female cercopithecine grooming was critically examined and alternative models suggested. These models, named ‘engagement’, ‘interference’ and ‘rank difference’, generated different predicted grooming distributions by assuming the operation of different constraints. These constrains were, respectively, the time available for grooming, active interference on the part of higher ranked animals and a depression of grooming relations as rank difference between animals grew. These priority of access models were compared with observed grooming patterns in two groups of free-ranging olive baboons, Papio cynocephalus anubis: one large, one small. The fit of these models was poor. An alternative method of examining the effects of rank on grooming behaviour using multiple regression was successful. In the small troop the rank of the groomee explained a significant amount of the variance in grooming whilst the rank distance between groomer and groomee did not. In the large troop the opposite effect was found. In the light of these results the merits of bottom-up modelling versus top-down description are discussed. The question of group size in primates and its relationship to social complexity are addressed.

Sex, kinship, and the evolution of social manipulation

Abstract In recent years kin selection has been widely used to explain social systems and the evolution of complex social traits. However, because a knowledge of kin is a prerequisite of kin selection theory, and because a male has less certainty of kin and, in many cases, few or none available to him within a social group, he will be unable to favor kin or benefit from them as reliably as will a female. It is predicted, therefore, that social strategies involving unrelated individuals will be more common among males than females and suggested that the greater encephalization among higher mammals, particularly primates, allowed complex nonkin strategies of social manipulation to evolve, realizing its greatest sophistication in human political systems. Finally, the question whether selection for certain types of social strategies in males may not have led to differences from females in assessment and manipulation skills is considered.

Translocation of Primates

Active primate conservation and management is becoming increasingly important to the long-term survival of populations and species as habitats are destroyed and animals exploited. The future of many species may depend on modifying current directions and exploring new survival possibilities. Translocation is an established but little used conservation and management technique for primates that may have great future potential.

Baboon cues for eating meat

Two types of manipulations were performed with a troop of predatory baboons to elucidate the cues which individuals use in eating meat. Gazelle carcasses which had been killed, consumed and abandoned by the baboons were presented to various members of the troop. Live domestic rabbits were also placed among the troop. Gazelle carcasses were eaten by individuals who had eaten from the carcass earlier in the day or who had seen other baboons eating the carcass, and were avoided by individuals who had no prior experience with the carcass. Rabbits were investigated, groomed or rejected although one predation did occur. These data suggest a complex process of evaluation in baboon meat-eating in which social cues can be an overriding factor. The data also argue for a conservatism in baboon consumption of meat which may have an evolutionary basis. Such a conservatism could provide an inhibition to scavenging among non-human primates and has implications for models of human evolution which posit a scavenging stage. These implications are discussed.

Reconciling aggression and social manipulation as means of competition. 1. Life-History perspective

I reexamined male competitive options via long-term data on adolescent and adult male consort success and data on male weights, age, size, residency status, and friendships with females collected from one troop of wild baboons. The options available to a male result from a complex interaction of variables and change with maturation, migration, and age. The acquisition of aggressive and social competence, the development of alternative nonaggressive strategies, the loss of physical prowess, and perhaps the effect of inbreeding avoidance all play a role. Aggressive and nonaggressive strategies may be mutually exclusive options for brief periods in a male’s life because of ontogenetic, historical, or physical constraints. But for most of the time, the two are likely to coexist. I assess the evolutionary significance of optional strategies of competition and discuss the conditions that might select for optional strategies.

Book Review: Primate Males. Peter M. Kappeler, Cambridge University Press, Cambridge, U.K., 2000, xii + 316pp.,

Thirty years ago I started my career by studying the role of females and males in baboon society. Very soon I was captivated (and hijacked) by the sheer complexity of the males. Meanwhile the field shifted emphasis from male to female strategies. Yet we all ended up in the same place, with the realization that you can’t understand one without the other. Despite its title, Primate Males takes this modern perspective. The book results from a conference held in late 1997 to provide a basic inventory of the causes and consequences of variation in primate group composition and social systems. The focus is ostensibly on how many males are in a group and what behaviors they exhibit, yet there is no chapter that is this narrow. The broader perspective is also evident in the organization of book sections. The introduction by Kappeler provides a brief historical look at explanations of social systems. Next comes a broadly comparative section that places primates in the context of male–female association in nonprimate species like birds (Davies) and macropods (Jarman). Also included here is a discussion by van Schaik on counterstrategies to infanticide that generalizes beyond primates to other mammals. The third section tackles the question of variation in number of males in primate groups. This is the majority of the book and includes lemurs (Kappeler), callitrichids (Heymann), cebids (Strier), guenons (Cords), papionines (Barton), red colobus (Struhsaker), gibbons (Sommer and Reichard), gorillas (Watts), and several chapters devoted to langurs both in comparative perspective (Sterck and van Hooff) and specific species (Steenbeek, Sterck, deVries, and van Hooff). Information on other species and taxa (Barbary macaques, savannah baboons, chimpanzees) are also in later sections, however. “Behavioral aspects of male coexistence” organizes the next chapters, which are an eclectic assortment of viewpoints on male behavior. Van Hooff emphasizes the complexity of interactions including many that are rarely considered. Nunn imports an economic model of collective action derived from research on humans to understand nonhuman