Social System of a Hybrid Baboon Group (Papio anubis × P. hamadryas)

We describe the social organization, mating system, and social structure of a group of hybrid baboons (Papio anubis×P. hamadryas) in Ethiopia's Awash National Park. The group contained elements of both hamadryas and anubis societies. Overall, the group was a multimale, multifemale group that lacked cohesion and frequently formed subgroups. Subgroup formation was more strongly associated with predation risk than food availability. Although there were several hamadryas-like one-male units OMUs within the group, there was no evidence of a hamadryas multilevel society. Male and female members of OMUs were phenotypically more hamadryas-like than non-OMU individuals. The group contained substantial variation in the strength of inter- and intrasexual bonds: some females primarily groomed males while other females primarily groomed females, and the patterns were consistent with the OMU substructure. Despite some promiscuous mating, mating was biased towards the hamadryas condition for all group members. Additionally, rates of immigration and emigration were very low, and mean pairwise relatedness within the group is rising. For measures of intersexual bonding, all members of the group were intermediate between anubis and hamadryas individuals in less hybridized groups. The group was phenotypically and behaviorally more intermediate than it was in the 1970s (Sugawara, K. (1988). Primates 29: 429–448.) and the changes may indicate a relatively young and dynamic hybrid zone.     

History and Present Scope of Field Studies on <Emphasis Type="Italic">Macaca fuscata yakui</Emphasis> at Yakushima Island,Japan

Field studies on Japanese macaques on Yakushima Island started in the mid-1970s, >25 yr after the emergence of Japanese primatology, in response to criticism of methods using provisioning and the desire to find the socioecological factors influencing the social life of macaques in natural habitats. We habituated macaques without provisioning mainly in the coastal warm-temperate forest and found that they lived in small troops with a high socionomic sex ratio. Observations of several troop fissions and troop takeovers by nontroop males suggest that Yakushima macaques have a different social organization from that of Japanese macaques in other habitats. For example, youngest ascendancy as the dominance relationhip among sisters, which usually occurs in provisioned troops, was absent in Yakushima macaques. We compared their ecological and social features with those of Japanese macaques at Kinkazan (cool-temperate forests) and found that abundance of high-quality foods may cause stronger intra- and intertroop competition at Yakushima. Female Yakushima macaques may more positively solicit nontroop males to associate with them during the mating season. Such a tendency may promote frequent male movement between troops and frequent troop fissions. Though ecological factors form social features of Japanese macaques, some features such as male association and movements between troops are not accounted for via socioecology. Recent field studies have focused on macaques living at higher altitudes in Yakushima and on individual survival strategies by taking diverse viewpoints and using new technologies. DNA analysis of fecal samples shows low genetic diversity and suggests the macaques’ recent expansion from lowland to highland forests in Yakushima. The population censuses conducted annually indicate that the higher-altitude macaques have a larger home range but a similar group size versus their counterparts at low elevations. The unsolved issues in socioecology will pose a challenge to the younger generation of primatologists. Conservation of macaques and their habitat is one of our major activities at Yakushima. The level of protection has gradually increased in the National Park at Yakushima and, via our various conservation efforts, its most important area was designated a World Heritage Site by UNESCO in 1993. However, large-scale logging in the 1960s and 1970s caused the loss of macaque habitats and led to increased crop damage by them in the 1980s. We have proposed effective methods to protect cultivated fields from macaques as well as several plans for sustainable use of forests, such as ecotourism and a fieldwork course for university students. Local residents and researchers have created several nongovernment organizations (NGOs) to promote conservation and nature study at Yakushima. The role of local NGOs is particularly important to mitigate conflicts between people and wildlife. Though hundreds of macaques are still captured as pests annually in Yakushima, we continue the conservation measures and spread awareness of conservation in cooperation with the local NGOs.     

Time Allocation Patterns of Lowland Woolly Monkeys (Lagothrix lagotricha poeppigii) in a Neotropical Terra Firma Forest

We investigated the time allocation decisions of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a terra firma forest in eastern Ecuador where they occur sympatrically with 9 other primate species. Woolly monkeys spent considerable amounts of time searching for and attempting to procure animal prey—roughly as much time as they spent consuming plant material: ripe fruits, leaves, and flowers. The amount of time spent foraging for animal prey is positively related to the habitat-wide availability of ripe fruits (the predominant component of the woolly monkey diet), and negatively related to both ambient temperature and the abundance of potential prey items in the habitat. Time spent resting showed exactly the opposite pattern with respect to these ecological variables. These results suggest that woolly monkeys follow an energy-maximizing strategy of food acquisition during times of fruit abundance—focusing on animal foods and perhaps laying down fat reserves to utilize when ecological conditions worsen—and follow an energy-minimizing strategy when fruit resources are scarce. Such a strong and seasonal commitment to animal prey foraging is unique among the ateline primates and is not ubiquitous even among lowland woolly monkeys. We suggest that this foraging strategy, and the greater intragroup cohesion that characterizes some populations of Lagothrix, are both opportunistic responses to regional differences in habitat quality. Identifying and accounting for such intraspecific variation should be a goal of any analysis of comparative socioecology.     

Gorilla society: What we know and don't know

Science is fairly certain that the gorilla lineage separated from the remainder of the hominoid clade about eight million years ago, 2 , 4 and that the chimpanzee lineage and hominin clade did so about a million years after that. 1 , 2 However, just this year, 2007, it was discovered that although the human head louse separated from the congeneric chimpanzee body louse (Pediculus) around the same time as the chimpanzee and hominin lineages split, 3 the human pubic louse apparently split from its sister species, the congeneric gorilla louse, Pthirus, 4.5 million years after their host lineages split. 3 No tested explanations exist for the discrepancy. Much is known about hominin evolution, but much remains to be discovered. The same is true of primate socioecology in general and gorilla socioecology in particular.     

Primate group size and interpreting socioecological models: Do folivores really play by different rules?

Because primates display such remarkable diversity, they are an ideal taxon within which to examine the evolutionary significance of group living and the ecological factors responsible for variation in social organization. However, as with any social vertebrate, the ecological determinants of primate social variability are not easily identified. Interspecific variation in group size and social organization results from the compromises required to accommodate the associative and dissociative forces of many factors, including predation, 1 - 3 conspecific harassment and infanticide, 4 - 6 foraging competition 1 , 7 and cooperation, 8 dominance interactions, 9 reproductive strategies, and socialization. 10 - 12 Causative explanations have emerged primarily through the construction of theoretical models that organize the observed variation in primate social organization and group size relative to measurable ecological variation.     

Introduction: Current studies on primate socioecology and evolution

Primate socioecology is being dramatically transformed as new studies are undertaken in Madagascar and the New World. Simultaneously, the incorporation of primate studies in a broader framework of theory in behavioral ecology promises to more intelligently inform anthropology's traditional concerns with primate and hominid evolution.     

The endemic seven: Four decades of research on the Sulawesi macaques

The oceanic island of Sulawesi, Indonesia, has long been of interest to scholars, including one of the leading evolutionary thinkers of the nineteenth century: Alfred Russell Wallace. During his explorations of the Malay archipelago, Wallace 1 was particularly struck with the ecology of Sulawesi (formally Celebes), noting the depauperate, yet distinctive nature of its fauna. It was home to members of both Asian and Australian faunas. Today, the asymmetrical four‐armed island of Sulawesi is regarded as the center of Wallacea, a unique biogeographical zone where endemism levels are incredibly high. 2 Of the 127 mammals indigenous to Indonesia, 79 (62%) are endemic to Sulawesi. Among these are seven species of the genus Macaca, 3 the most geographically widespread and ecologically diverse of nonhuman primate genera. In this paper, I trace the history and development of the major research trends on these endemic primates over the last four decades since Fooden's 3 landmark 1969 publication. These research trends include origin, speciation, and taxonomy; socioecology and behavior; ecology and conservation; and, most recently, the human‐macaque interface.     

Time Constraints Limit Group Sizes and Distribution in Red and Black-and-White Colobus

Researchers have shown that, in frugivorous primates, a major constraint on group size is intra group feeding competition. The relationship is less obvious in folivorous primates. We investigated whether colobine group sizes are constrained by time limitations as a result of their low energy diet and ruminant-like digestive system. We used climate as an easy to obtain proxy for the productivity of a habitat. Using the relationships between climate, group size, and time budget components for populations of Colobus and Piliocolobus at different research sites, we created 2 taxon-specific models. In both genera, feeding time increased with group size or biomass. The models for Colobus and Piliocolobus correctly predicted the presence or absence of the genera at, respectively, 86% of 148 and 84% of 156 African primate sites. Median predicted group sizes where the respective genera were present are 19 for Colobus and 53 for Piliocolobus. We show that the differences between the 2 genera are due mainly to intrinsic differences in the way each taxon’s digestive physiology interacts with climatic variables to influence resting time requirements. The models may help us explore their responses to climatic change in both the past and the future.