Genetic evidence for dispersal by both sexes in the Central American Squirrel Monkey, Saimiri oerstedii citrinellus

Sex-biased dispersal (SBD) is common in many vertebrates, including primates. However, dispersal patterns in New World primates may vary among closely related taxa or populations in different local environments. Here, we test for SBD in an endangered New World primate, the Central American Squirrel Monkey (Saimiri oerstedii citrinellus). Previous studies of behavioral ecology suggest predominantly female dispersal in S.o. oerstedii in the Southern Pacific region of Costa Rica. However, our genetic data do not support strongly female-biased dispersal in S.o. citrinellus in the Central Pacific region. Our tests for SBD using microsatellite data including comparisons of isolation-by-distance, AI(c) , and F(ST) values between males and females were not significant. Also, we found greater population genetic structure in mitochondrial markers than in microsatellite markers, indicative of predominantly male dispersal. We conclude that both sexes disperse in S.o. citrinellus, and that males probably disperse over longer distances. We discuss how spatial and temporal variation among local populations should be taken into account when studying dispersal patterns and especially sex bias.

Flexible and conservative features of social systems in tufted capuchin monkeys: comparing the socioecology of Sapajus libidinosus and Sapajus nigritus

Socioecological models assume that primates adapt their social behavior to ecological conditions, and predict that food availability and distribution, predation risk and risk of infanticide by males affect patterns of social organization, social structure and mating system of primates. However, adaptability and variation of social behavior may be constrained by conservative adaptations and by phylogenetic inertia. The comparative study of closely related species can help to identify the relative contribution of ecological and of genetic determinants to primate social systems. We compared ecological features and social behavior of two species of the genus Sapajus, S. nigritus in Carlos Botelho State Park, an area of Atlantic Forest in São Paulo state, and S. libidinosus in Fazenda Boa Vista, a semi-arid habitat in Piauí state, Brazil. S. libidinosus perceived higher predation risk and fed on clumped, high quality, and usurpable resources (fruits) all year round, whereas S. nigritus perceived lower predation risk and relied on evenly distributed, low-quality food sources (leaves) during periods of fruit shortage. As predicted by socioecology models, S. libidinosus females were philopatric and established linear and stable dominance hierarchies, coalitions, and grooming relationships. S. nigritus females competed less often, and could transfer between groups, which might explain the lack of coalitions and grooming bonds among them. Both populations presented similar group size and composition and the same polygynous mating system. The species differed from each other in accordance with differences in the characteristics of their main food sources, as predicted by socioecological models, suggesting that phylogenetic inertia does not constrain social relationships established among female Sapajus. The similarity in mating systems indicates that this element of the social system is not affected by ecological variables and thus, is a more conservative behavioral feature of the genus Sapajus.

Even adult sex ratios in lemurs: Potential costs and benefits of subordinate males in Verreaux's sifaka (Propithecus verreauxi) in the Kirindy Forest CFPF, Madagascar

Optimal group size and composition are determined by both the costs and benefits of group living for the group's members. Verreaux's sifakas (Propithecus verreauxi), a diurnal lemur, form multimale multifemale groups with the tendency toward even adult sex ratios despite a small average number of females per group. The unexpected presence of multiple adult males may be explained by tolerance of other group members if subordinate males provide benefits to the group that outweigh the costs associated with their presence. Results based on both demographic data collected over a 13-year period and behavioral observations suggest that subordinate males provide no benefits in terms of infant survival and defense against group takeover by outside males. Although groups with more males are more likely to win intergroup encounters, subordinate males do not participate in these encounters more often than expected. Subordinate males are not costly to other group members in terms of direct intragroup feeding competition, but aggression rates between dominant and immigrated subordinate males increase in the mating season. Even though subordinate males provide very few benefits to the group, they are not very costly either and thus may be tolerated by resident females and dominant males. This tolerance may help to partially explain the tendency towards their unusual adult sex ratio.

The Effects of Kin on Primate Life Histories

Advances in our understanding of primate life histories and dispersal patterns provide insights into the ways in which facultative responses to local ecological and demographic conditions are mediated by phylogenetic constraints. The long life spans characteristic of primates provide the necessary conditions for overlapping generations of related individuals to maintain extended kin bonds. Dispersal regimes dictate the opportunities for biological kin to interact with one another and define the range of potential reproductive and social partners within and beyond their natal groups. Dispersal patterns also affect variation in components of life histories such as female age at first reproduction, reproductive rates, and trade-offs between investment in current vs. future offspring and extended kin. Understanding these dynamics has important implications for assessing the viability of small populations and the ability of different primates to adapt.

Controversy over the application of current socioecological models to folivorous primates:Colobus vellerosus fits the predictions

We explore the applicability of the current socio-ecological model to characterize the social structure of Colobus vellerosus, a folivorous primate. The current socio-ecological model predicts that female social relationships should respond in predictable ways to food abundance and distribution and associated competitive regimes. It appears to successfully explain variation in social structure in some primate species; however, recent research indicates that several folivorous or folivore-frugivorous species seem to be exceptions. We present data on social relationships and social structure in two groups of C. vellerosus over 15 months at Boabeng-Fiema, Ghana. As predicted by the model, our results indicate the co-occurrence of 1) low levels of grooming between female C. vellerosus when compared with other species, 2) an absence of female coalitions over food, and 3) female dispersal. Taken together, these traits suggest a "Dispersal-Egalitarian" species. However, our results also indicate female-female affiliation was higher than male-female affiliation, which was more indicative of a "female resident" species. Our data also suggests inter-sexual affiliation varied among groups. This variation in inter-sexual affiliation could be due to variation in the intensity of infanticidal threats between groups. The combination of these social characteristics lead us to conclude that C. vellerosus' social structure is largely congruent with the ecological indicators of food distribution and female competitive regime that we have previously documented, which indicated high quality foods were not monopolizable or usurpable and behavioral evidence of within-group contest competition (i.e. supplantations over food) was rare. But the combination of higher female-female affiliation (compared to male-female) and female dispersal is difficult to explain in light of predictions, unless future work reveals female residency is more predominant than female dispersal in our population. We also discuss reasons why some folivores do not appear to fit the predictions of the current socio-ecological model.

Exchange, affiliation, and protective interventions in semifree-ranging brown capuchin monkeys (Cebus apella)

The "social intelligence" hypothesis proposes that intelligence evolved as a consequence of the need for behavioral maneuvering to deal with the complexities of social life. As a result, coalitions have received considerable attention. Here we present the patterns of coalitionary behavior observed in a semifree-ranging group of Cebus apella and explore the effects of kinship, spatial proximity, and rank. In contrast to descriptions of Old World monkeys and to some descriptions of capuchins, kinship did not influence the pattern of coalitionary behavior, although individuals tended to help those that remained in close proximity. Rank had the greatest influence on coalitions: those that interfered in conflicts (often the alpha) were higher ranking than both contestants and supported the most subordinate (younger) interactant. However, rank did not influence the coalitionary support when conflicts involved only adults. We found no evidence that individuals were making use of triadic knowledge, and most of the coalitions can best be described as protective interventions involving immatures. The overall low rate of coalitions may be due to a period of social stability.

Fifty years of chimpanzee demography at Taronga Park Zoo

There has been a captive Pan troglodytes colony at Taronga Park Zoo in Sydney, Australia, since the mid-1930s. Demographic data on these animals were first analyzed in 1986; however, further information collected for 15 years since then is now available. The reproductive histories of 33 females in the colony have been recorded, and these data form the largest collection of captive chimpanzee data from a setting that has involved natural breeding conditions since the mid-1960s. These data were analyzed in conjunction with data from wild populations to establish the degree of variability present within chimpanzee reproductive parameters, and to identify which distinctive life history characteristics persist in well-provisioned, natural-fertility populations. The age at first birth for the chimpanzee females is 9.8 yr on average (n=16), which is 1-4.8 yr earlier than the average for wild populations. In line with this accelerated reproduction, birth intervals are also significantly shorter than those in noncaptive chimpanzee populations. The median birth interval for all surviving infants (based on a Kaplan-Meier survival analysis) is 49 months (n=43) compared to 62+ months for wild groups. At the same time, infant mortality remains high. The data confirm distinctive features of the life history of common chimpanzees, including later maturation, long birth intervals, a relatively invariant fertility schedule, and high juvenile mortality. However, aspects of both fertility and mortality are significantly related to social circumstances, indicating that in common chimpanzees, as in humans, life history characters may represent ecological and social adaptations rather than species-fixed characteristics.

Molecular genetic approaches to the study of primate behavior, social organization, and reproduction

In the past several decades, the development of novel molecular techniques and the advent of noninvasive DNA sampling, coupled with the ease and speed with which molecular analyses can now be performed, have made it possible for primatologists to directly examine the fitness effects of individual behavior and to explore how variation in behavior and social systems influences primate population genetic structure. This review describes the theoretical connections between individual behavior and primate social systems on the one hand and population genetic structure on the other, discusses the kinds of molecular markers typically employed in genetic studies of primates, and summarizes what primatologists have learned from molecular studies over the past few decades about dispersal patterns, mating systems, reproductive strategies, and the influence of kinship on social behavior. Several important conclusions can be drawn from this overview. First, genetic data confirm that, in many species, male dominance rank and fitness are positively related, at least over the short term, though this relationship need not simply be a reflection of male-male contest competition over mates. More importantly, genetic research reveals the significance of female choice in determining male reproductive success, and documents the efficacy of alternative mating tactics among males. Second, genetic data suggest that the presumed importance of kinship in structuring primate social relationships needs to be evaluated further, at least for some taxa such as chimpanzees in which demographic factors may be more important than relatedness. I conclude this paper by offering several suggestions of additional ways in which molecular techniques might be employed in behavioral and ecological studies of primates (e.g., for conducting "molecular censuses" of unhabituated populations, for studying disease and host-parasite interactions, or for tracking seed fate in studies of seed dispersal) and by providing a brief introduction to the burgeoning field of nonhuman primate behavioral genetics.

Primatology comes of age: 2002 AAPA Luncheon address

The growth of primate field studies has occurred along multiple dimensions representing expansion in the number of species studied, comparative studies of different populations of the same species, and populations and groups studied over time. The accumulation of data on a broader taxonomic diversity of primates has contributed to advances in the use of comparative methods for gaining insights into interspecific variation in behavior patterns, but the incorporation of intraspecific variation into comparative models of behavior has lagged behind. This delay can be attributed, in part, to the slow rate at which the interacting effects of life history and demography on behavior emerge in slow-growing, long-lived primates. It may also reflect the anthropocentric foundation of field primatology, which historically focused on interspecific comparisons with humans instead of interpopulation variation among primates. Conservation concerns have stimulated new thinking about the importance of populations and the range of behavioral variation that populations maintain. The integration of intra- and interspecific behavioral variation will distinguish the next generation of comparative models in primatology, and set a new agenda as field primatology comes of age.

Are subordinates always stressed? A comparative analysis of rank differences in cortisol levels among primates

Among primate species there is pronounced variation in the relationship between social status and measures of stress physiology. An informal meta-analysis was designed to investigate the basis of this diversity across different primate societies. Species were included only if a substantial amount of published information was available regarding both social behavior and rank-related differences in stress physiology. Four Old World and three New World species met these criteria, including societies varying from small-group, singular cooperative breeders (common marmoset and cotton top tamarin) to large-troop, multi-male, multi-female polygynous mating systems (rhesus, cynomolgus, talapoin, squirrel monkeys, and olive baboon). A questionnaire was formulated to obtain information necessary to characterize the stress milieu for individuals in particular primate societies. We standardized cortisol values within each species by calculating the ratio of basal cortisol concentrations of subordinates to those of dominants in stable dominance hierarchies and expressing the ratio as a percentage (relative cortisol levels). The meta-analysis identified two variables that significantly predicted relative cortisol levels: subordinates exhibited higher relative cortisol levels when they (1). were subjected to higher rates of stressors, and (2). experienced decreased opportunities for social (including close kin) support. These findings have important implications for understanding the different physiological consequences of dominant and subordinate social status across primate societies and how social rank may differ in its behavioral and physiological manifestations among primate societies.

A cross-cultural analysis of the behavior of women and men: implications for the origins of sex differences

This article evaluates theories of the origins of sex differences in human behavior. It reviews the cross-cultural evidence on the behavior of women and men in nonindustrial societies, especially the activities that contribute to the sex-typed division of labor and patriarchy. To explain the cross-cultural findings, the authors consider social constructionism, evolutionary psychology, and their own biosocial theory. Supporting the biosocial analysis, sex differences derive from the interaction between the physical specialization of the sexes, especially female reproductive capacity, and the economic and social structural aspects of societies. This biosocial approach treats the psychological attributes of women and men as emergent given the evolved characteristics of the sexes, their developmental experiences, and their situated activity in society.

Scale issues in the study of primate foraging: red colobus of Kibale National Park

Diet data have been used to address a number of theoretical issues. We often calculate the proportion of time spent eating different foods (e.g., fruits, leaves) to place species into dietary categories and contrast morphological or behavioral traits among categories. Yet we have little understanding of how flexible species can be in terms of the plant parts and species consumed. To address this issue, we analyzed data on the diets of red colobus monkeys (Procolobus badius) from Kibale National Park, Uganda, to evaluate temporal and spatial variability in the plant parts and species eaten. After considering observer differences and sampling issues, we evaluated how different a group's diet could be if samples were taken in different years. We found that the diet of the same groups showed significant, consistent changes over a 4-year period. For example, the time spent feeding on leaves increased from 56% in 1994 to 76% in 1998. The plant parts and species eaten by eight groups inhabiting different types of forest (e.g., pristine, logged, riverine) varied among groups. The largest interdemic difference was seen in the use of young leaves (38%). Dietary differences were also found between groups with overlapping home ranges (41-49% overlap). Different subspecies of Procolobus badius also varied in diet; however, this variation was often not of the magnitude documented within Kibale for the same population. The fact that diet can vary considerably over small spatial and short temporal scales within the same species raises the intriguing question as to what level of interspecific difference is biologically significant for addressing particular questions. We conclude that behavioral flexibility blurs our traditional stereotypic assessment of primates; a study of one group that occupies a specific habitat at one point in time may not adequately represent the species.

Determinants of female dispersal in Thomas langurs

Female dispersal occurs in a number of primate species. It may be related to: avoidance of inbreeding, reduction in food competition, reduction of predation risk, or avoidance of infanticide in combination with mate choice. Female dispersal was studied for a 5-year period in a wild population of Thomas langurs (Presbytis thomasi) that lived in one-male multi-female groups. Juvenile and adult individuals of both sexes were seen to disperse. Females appeared to transfer unhindered between groups, mostly from a larger group to a recently formed smaller one. They transferred without their infants and when not pregnant, and seemed to transfer preferentially during periods when extra-group males were harassing their group. During these inter-group encounters extra-group males seemed to try to commit infanticide. Thus, the timing of female transfer was probably closely linked to infanticide avoidance. Moreover, females seemed to transfer when the resident male of their group was no longer a good protector. The observations in the present study suggest that females transferred to reduce the risk of infanticide. Female dispersal may have another ultimate advantage as well, namely inbreeding avoidance. Due to the dispersal of both females and males the social organization of Thomas langurs was rather fluid. New groups were formed when females joined a male; male takeovers were not observed. Bisexual groups had only a limited life span, because all adult females of a bisexual group could emigrate. This pattern of unhindered female dispersal affects male reproductive strategies, and in particular it might lead to infanticidal behavior during inter-group encounters.

Female dispersal, social organization, and infanticide in langurs: are they linked to human disturbance?

Female dispersal in gregarious animals can involve the desertion of a site, desertion of a social group, or both. Group desertion may be related to inbreeding avoidance. Group fidelity may result from cooperation among females in a group. Site fidelity will be more likely when food can be monopolized and when the population density is close to habitat saturation. The degree of habitat saturation was approximated with a measure of human disturbance. The influence of these various factors on the incidence of female dispersal was investigated for langur populations using data from the literature. The results suggest that female dispersal in langurs involved site desertion, not group desertion. The incidence of female dispersal may affect the social organization of langurs. I propose that when females do not disperse, male takeovers prevail, whereas in populations where female dispersal regularly occurs bisexual groups are disbanded or new groups are formed, a process I call female split-merger. Male takeover is thought to occur when site fidelity is high, female split-merger when site fidelity is low. These processes were indeed found to occur in these circumstances. The dispersal of females might prevent infanticide, whereas male takeover might promote it. Indeed, in studies with male takeover, more infants fell victim to infanticide than in studies with female split-merger. Therefore, female dispersal in langurs is an effective female counterstrategy to infanticide. The factor that had the most profound effect on female dispersal, social organization, and infanticide was habitat saturation. Habitat saturation was measured as the degree of human disturbance, and its influence on the behavior of langurs is probably of relatively recent date. This may lead to an evolutionary transient situation and may explain the discrepancy between current socioecological theories and the behavior of langurs in populations lacking female dispersal.

Display of proceptive behaviors in relation to urinary and fecal progestin levels over the ovarian cycle in female tufted capuchin monkeys

In many primates species, female sexual attractivity is influenced by behavioral cues as well as by nonbehavioral cues (i.e., visual-morphological or chemical signals). Both kinds of cues are usually related to the ovarian cycle and female hormonal state. Female tufted capuchins (Cebus apella) lack any external morphological change in relation to the ovarian cycle and evidence of scent-marking behavior has never been reported. In addition, tufted capuchin males do not routinely investigate the female's body or urine. Instead, capuchin females are extremely active in sexually soliciting the male(s) and their courtship toward them involves a rich behavioral repertoire. In the present study we defined female tufted capuchin proceptivity and investigated its relationship with female reproductive state. Ovarian hormones were measured in urine and fecal samples from four captive females in order to (a) assess their reliability for monitoring female ovarian function and (b) provide information on the timing of the component cycle phases and in particular the periovulatory phase. Measurements of urinary and fecal progestin metabolites provided the best indicator of ovarian cyclicity and for timing of the periovulatory phase. Through a multivariate analysis of the behavioral data set we distinguished four behaviors (eyebrow raising with vocalization, touching-and-running, nuzzling and head cocking) which showed a marked cyclicity (21.3 days) that matched that of urinary progesterone (21.9 days). Data showed that each period of proceptive behaviors was 2.7 +/- 0.8 days long and the day of a defined luteal phase rise in urinary progesterone levels was markedly shifted toward the end of this period. Furthermore, the ejaculations observed always occurred within proceptive periods. The results clearly indicate that female behavior is a good indicator of the periovulatory phase and can enhance female attractivity.

Whither Primatology? The Place of Primates in Contemporary Anthropology

▪ Abstract  Primatology in anthropology began with morphological comparisons of primates to reconstruct the evolution of humans. Naturalistic studies started in the mid-twentieth century and contributed to understanding the functions of morphological variations. Today, research in primatology employs the new paradigm of behavioral ecology and sociobiology for analysis and interpretation of variation in behavior and ecology. Grouping and group sizes of primates are explained with reference to effects of predation, defense of resources, and female defense against male infanticide. Primates avoid close consanguineous mating, usually by dispersal of males from the birthplace, though in bonobos and chimpanzees males are philopatric. In many primates, nepotistic relations among females are explained by kin selection operating on the philopatric sex. In chimpanzees, nepotism is clearest among the philopatric males. Sexual dimorphism, dominance hierarchies, intrasexual competition, and particularly infanticide by males are best explained by the action of sexual selection. Comparative studies of primates indicate that the large brains of the genus Homo (enlarged cerebral cortex) evolved after bipedalism and human dental characters and probably depended on high-quality diets. Broad comparative studies have supported the hypothesis that large brains may have evolved in response to complex social environments, but comparisons within the apes only may not support the hypothesis. Although dominant themes of current anthropology are not compatible with the epistemology, theory, or methodology of primate research and interpretation, primate studies fit easily within the future of anthropology as a four-field evolutionary study of the origins of humans and human nature.

Body fat and time of year interact to mediate dispersal behaviour in ground squirrels

Behaviour is often influenced by energy availability. Hibernation presents an energetic challenge to Belding's ground squirrels, Spermophilus beldingi, which depend entirely on stored energy for survival during their 8-9 month dormant period each year. Dispersal from the natal area may also place energetic demands on S. beldingi. In this study, we assessed the relationship between dispersal behaviour, body mass and body fat of juvenile male S. beldingi over 3 consecutive years, one of which had a substantially delayed juvenile active season due to heavy spring snowfall. We evaluated body fat using the non-destructive method of measuring electrical conductivity of the body. When the active season began late, acquisition of body mass and body fat were accelerated, and dispersal behaviour was inhibited. These results suggest that the ontogeny of mass and fat gain in juvenile male S. beldingi is influenced by a seasonal time-keeping mechanism. Energy allocation was hierarchical in S. beldingi, with pre-hibernation fattening taking precedence over dispersal. Physiological signals reflecting body fat content appear to interact with an endogenous timing mechanism in this species to regulate the dispersal behaviour of juvenile males.\C 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

Grooming down the hierarchy: allogrooming in captive brown capuchin monkeys, Cebus apella

Observations of captive female brown capuchin monkeys in five groups revealed that grooming is primarily the occupation of dominant females at both the individual and dyadic levels. When categorized according to rank class, alpha females were the only class to perform significantly more grooming than they received. These results are inconsistent with reports on vervets, baboons and macaques, and suggest that grooming in capuchin monkeys may have different functions from those reported for cercopithecine primates. A dyadic analysis revealed, however, that grooming occurred more often between closely ranked females, similar to what is seen in several Old World monkey species. Therefore, some aspects of grooming in capuchins are similar to that seen in Old World monkeys, but the way they distribute grooming is different, which may prompt a re-evaluation of current theories regarding the social function of allogrooming in non-human primates.