Chimpanzees (Pan troglodytes) in savanna landscapes.

Chimpanzees (Pan troglodytes) are the only great apes that inhabit hot, dry, and open savannas. We review the environmental pressures of savannas on chimpanzees, such as food and water scarcity, and the evidence for chimpanzees' behavioral responses to these landscapes. In our analysis, savannas were generally associated with low chimpanzee population densities and large home ranges. In addition, thermoregulatory behaviors that likely reduce hyperthermia risk, such as cave use, were frequently observed in the hottest and driest savanna landscapes. We hypothesize that such responses are evidence of a "savanna landscape effect" in chimpanzees and offer pathways for future research to understand its evolutionary processes and mechanisms. We conclude by discussing the significance of research on savanna chimpanzees to modeling the evolution of early hominin traits and informing conservation programs for these endangered apes.

The influence of phylogeny, social style, and sociodemographic factors on macaque social network structure.

Among nonhuman primates, the evolutionary underpinnings of variation in social structure remain debated, with both ancestral relationships and adaptation to current conditions hypothesized to play determining roles. Here we assess whether interspecific variation in higher-order aspects of female macaque (genus: Macaca) dominance and grooming social structure show phylogenetic signals, that is, greater similarity among more closely-related species. We use a social network approach to describe higher-order characteristics of social structure, based on both direct interactions and secondary pathways that connect group members. We also ask whether network traits covary with each other, with species-typical social style grades, and/or with sociodemographic characteristics, specifically group size, sex-ratio, and current living condition (captive vs. free-living). We assembled 34-38 datasets of female-female dyadic aggression and allogrooming among captive and free-living macaques representing 10 species. We calculated dominance (transitivity, certainty), and grooming (centrality coefficient, Newman's modularity, clustering coefficient) network traits as aspects of social structure. Computations of K statistics and randomization tests on multiple phylogenies revealed moderate-strong phylogenetic signals in dominance traits, but moderate-weak signals in grooming traits. GLMMs showed that grooming traits did not covary with dominance traits and/or social style grade. Rather, modularity and clustering coefficient, but not centrality coefficient, were strongly predicted by group size and current living condition. Specifically, larger groups showed more modular networks with sparsely-connected clusters than smaller groups. Further, this effect was independent of variation in living condition, and/or sampling effort. In summary, our results reveal that female dominance networks were more phylogenetically conserved across macaque species than grooming networks, which were more labile to sociodemographic factors. Such findings narrow down the processes that influence interspecific variation in two core aspects of macaque social structure. Future directions should include using phylogeographic approaches, and addressing challenges in examining the effects of socioecological factors on primate social structure.

Diet and Activity of Macaca assamensis in Wild and Semi-Provisioned Groups in Shivapuri Nagarjun National Park, Nepal.

Studying the behavioural flexibility and adaptability of macaques to different habitats is one approach to designing a conservation plan. To determine the activity budget and feeding behaviour and evaluate the effects of seasonality in wild and human- altered habitats of Assamese macaques (Macaca assamensis), we conducted this study in the Nagarjun forest of Shivapuri-Nagarjun National Park (SNNP) in central Nepal. We also updated the list of plant food items of Assamese macaques in the SNNP. Using scan and all-occurrence sampling, we recorded the diets and activities of Assamese macaques in 2 social groups, a wild-feeding group (WG) and a semi-provisioned group (SPG), throughout the year from August 2013 to July 2014. Both groups spent most of their time in feeding activities and were quite arboreal, but there were significant differences in the activity budgets and diets between the groups. Human food was the main component of the diet for the SPG, whereas it was fruit for the WG, indicating a normally frugivorous diet. Furthermore, the activity budget and diet composition varied in response to the season. These results indicate that provisioning alters the activity and feeding behaviour of macaques, and can also increase human-macaque conflict and disease transmission.

Hierarchical steepness, counter-aggression, and macaque social style scale.

Nonhuman primates show remarkable variation in several aspects of social structure. One way to characterize this variation in the genus Macaca is through the concept of social style, which is based on the observation that several social traits appear to covary with one another in a linear or at least continuous manner. In practice, macaques are more simply characterized as fitting a four-grade scale in which species range from extremely despotic (grade 1) to extremely tolerant (grade 4). Here, we examine the fit of three core measures of social style-two measures of dominance gradients (hierarchical steepness) and another closely related measure (counter-aggression)-to this scale, controlling for phylogenetic relationships. Although raw scores for both steepness and counter-aggression correlated with social scale in predicted directions, the distributions appeared to vary by measure. Counter-aggression appeared to vary dichotomously with scale, with grade 4 species being distinct from all other grades. Steepness measures appeared more continuous. Species in grades 1 and 4 were distinct from one another on all measures, but those in the intermediate grades varied inconsistently. This confirms previous indications that covariation is more readily observable when comparing species at the extreme ends of the scale than those in intermediate positions. When behavioral measures were mapped onto phylogenetic trees, independent contrasts showed no significant consistent directional changes at nodes below which there were evolutionary changes in scale. Further, contrasts were no greater at these nodes than at neutral nodes. This suggests that correlations with the scale can be attributed largely to species' phylogenetic relationships. This could be due in turn to a structural linkage of social traits based on adaptation to similar ecological conditions in the distant past, or simply to unlinked phylogenetic closeness.

Seasonal food changes and feeding behaviour adaptations of savanna chimpanzees at Nguye in Ugalla, Tanzania.

We studied the feeding strategies of savanna chimpanzees (Pan troglodytes) at Nguye in Ugalla, Western Tanzania (05°13'S, 30°28'E). Among the driest most open chimpanzee habitats, Ugalla is covered mainly by woodlands. We analysed undigested contents in chimpanzee faeces, and conducted a vegetation survey and a 1-year phenology survey every 2 weeks. The fruits of some trees with the highest biomass had high appearance rates in faeces (e.g. Parinari curatellifolia and Diplorhynchus condylocarpon). Herbaceous Aframomum mala fruits grew in large patches in savanna woodland near forest edges along rivers and had the highest appearance frequency over the longest seasonal period in faeces. Other species with higher appearance rates in faeces for long seasonal periods included Grewia mollis at the forest edge and Thespesia garckeana growing on termite mounds at the forest edge. These two tree species had low biomass. Thus, savanna chimpanzees fed on some tree foods with higher biomass, herbaceous fruits instead of scarcer tree fruits, and fruits at forest edges and in forests which occupy a small portion of the study area, in addition to woodlands which occupy a large proportion. The forest edge and interior run continuously for long distances along rivers. Forest occupies 2% of this area, but chimpanzees can continuously obtain food by moving along riverine forest. To compensate for fruit scarcity in the non-fruiting (early rainy) season, chimpanzees ate fibrous, low-quality plant parts. Chimpanzees formed smaller parties when ripe fruits and unripe legumes were scarcer. Using these feeding strategies, chimpanzees adapted to savanna woodlands.

Comparative ecological and behavioral study of Macaca assamensis and M. mulatta in Shivapuri Nagarjun National Park, Nepal.

Resource partitioning reduces the competition between different species within the same habitat, promoting their coexistence. To understand how such species co-adapt to reduce conflicts, we examined the behavior of two primates, Assamese macaque (Macaca assamensis) and rhesus macaque (Macaca mulatta), from April 2017 to March 2018 in Sivapuri Nagarjun National Park (SNNP), Kathmandu Valley, Nepal. We performed 1580 and 1261 scan sessions on wild multi-male/multi-female groups of Assamese and rhesus macaques, respectively, at 15-min sampling intervals. Assamese macaques consumed fewer plant species (38 species) than rhesus macaques (88 species). Overlapping food sources between the macaque species resulted in a Pianka index of 0.5. Assamese macaques consumed more items of tree, climber, and vine species, whereas rhesus macaques fed on more shrub, herb, and grass species. The proportions of plant parts consumed by the two species differed-more leaves, fruits and cones were used by Assamese macaques than rhesus macaques, whereas more flowers, seeds, and pods were consumed by rhesus macaques than Assamese macaques. Assamese macaques had a smaller home range (0.55 km2) than rhesus macaques (4.23 km2), and Assamese macaques had a shorter daily moving distance (1.6 km) than rhesus macaques (4.0 km). Although feeding time did not differ between the two macaque species, less time was devoted to social activities by Assamese macaques (16.0%) than by rhesus macaques (33.7%). Assamese macaques were generally arboreal, with 94.0% of their activities in trees, whereas rhesus macaques were largely terrestrial, with 58.5% of their activities on the ground. These differences in food selection, home-range size, ranging and activity patterns, and habitat use suggest that Assamese and rhesus macaques reduce resource competition through resource partitioning to coexist in a landscape matrix.

The influence of snowfall, temperature and social relationships on sleeping clusters of Japanese monkeys during winter in Shiga Heights.

We studied Japanese monkeys (Macaca fuscata) of the Shiga A(1) troop at their sleeping sites in Shiga Heights, Japan, for 41 nights during 3 winters. Monkeys chose their sleeping sites in Japanese cedars and in deciduous broad-leaved forests on non-snowing nights and in Japanese cedar forests on snowing nights. We counted 399 sleeping clusters in which 2 or more monkeys remained in physical contact through the night and 43 solitary sleeping monkeys, though monkeys did not maintain physical contact with others in the daytime. We found 397 clusters on tree branches and 2 clusters on rocks. The mean size of huddling clusters was 3.06+/-1.22 SD. The cluster size (3.17+/-1.26 SD) at lower ambient temperatures between -7 and -4 degrees C was larger than that at higher temperatures between -2 and 4 degrees C (cluster size 2.88+/-1.13 SD). Most clusters were composed of kin. Females kept close to related females in the daytime and huddled with them at night. The highest-ranking male mainly huddled with his kin and his familiar females. Other males kept farther apart from each other in the daytime, probably to avoid social conflicts. Through cold winter nights, however, such males reduced inter-individual distances and huddled with other males. Japanese monkeys appear to recognize three types of inter-individual distances: an intimate distance less than 1 m, a personal distance of 1-3 m and a social distance of 3-20 m; they change their inter-individual distances according to social and ecological circumstances.

Recognition of social relationships in bridging behavior among Tibetan macaques (Macaca thibetana).

Bridging behavior among male Tibetan macaques (Macaca thibetana) was studied in a free-ranging group at Mt. Huangshan, China. This behavior was defined as a type of affiliative behavior in which two individuals simultaneously lifted up one infant. Bridging behavior occurred after an adult male carried an infant to another male or approached another male who was holding an infant. Each male frequently held and groomed a particular infant in the group, which was named an "affiliated" infant of the male. Males were more frequently provided with their affiliated infant by other males than with other non-affiliated infants. This finding suggests that male Tibetan macaques recognized the affiliative relationship between a male and his affiliated infant, and chose that infant for bridging behavior on the basis of this knowledge. Such choice might be important for effective bridging behavior or other affiliative interactions between males. © 1995 Wiley-Liss, Inc.

Sleeping site selection by savanna chimpanzees in Ugalla, Tanzania.

We examined sleeping site selection by chimpanzees (Pan troglodytes) in the Ugalla savanna woodland area, western Tanzania, from 1994 to 2012. We established 488 km of line transects and recorded 379 chimpanzee beds within 30 m perpendicular to the transects. Comparisons between 60 × 60 m(2) quadrats containing new and recent beds and the remaining quadrats without beds along the transects indicated that evergreen forests accounted for disproportionately more area in quadrats with beds than in those without beds during both the dry and rainy seasons. In Ugalla, chimpanzees coexist with lions (Panthera leo) and leopards (Panthera pardus). They may sleep in forests to reduce predation risk by these carnivores, as trees are dense and the canopy is high and closed. The angle of slope was steeper in quadrats containing beds than in those without beds during the dry season, whereas the angle was less steep in quadrats with beds than in those without beds during the rainy season. Additionally, fewer beds were found further from forests. The distance between beds and forests during the dry season was shorter than that during the rainy season. Chimpanzees may sleep in or near forests and on slopes because of water pools in the valley forests along the slopes during the dry season. Quadrats with beds were at slightly higher altitude than those without beds during the rainy season; however, the difference was not significant during the dry season. The number of beds found in or close to feeding trees was not related to the fruiting period. Sleeping site selection by chimpanzees may be affected by predation pressure and water availability in the savanna woodland area.

Shape of, and body direction in, huddles of Japanese macaques (Macaca fuscata) in Arashiyama, Japan.

We studied huddles of Japanese macaques (Macaca fuscata) in the Arashiyama E troop at the "Arashiyama Monkey Park, Iwatayama" of Kyoto, central Japan. The macaques made physical contact with other individuals and formed huddles when the air was cold. The 99-101 adult females and 26-36 adult males in the study troop formed 345 huddles during 42 scan samples in the winter of 2001 and 376 huddles during 52 scan samples in the winter of 2002. The average size of huddles was 2.3 (range 2-7) individuals. Males huddled less frequently than females. Maternal kin-related dyads formed 2-female huddles more frequently than unrelated dyads. Choice of huddling partners might restrict the size of huddles. The most frequently observed 3 and 4-member huddles were triangular and diamond-shaped. Macaques usually huddled ventro-ventrally, ventro-laterally, and ventro-dorsally. A third individual frequently placed the ventral part of its body against the first individual and simultaneously put the lateral part of its body against the second individual, so that the 3 individuals formed a triangular huddle. This behaviour indicates that Japanese macaques choose their position and body direction in the huddle to reduce the area of body surface exposed to the air, thereby conserving body heat.