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Gibbons' loud morning songs are hypothesized to function in territorial defense. To efficiently defend their territory, gibbons could sing more frequently along the territory boundary. Alternatively, singing may advertise occupancy of a territory, regardless of the singer's location. Further, gibbons should choose singing sites that facilitate sound transmission. We investigated singing site choice of two groups of cao vit gibbon (Nomascus nasutus) from 2008-2009 and 2012-2013, in Bangliang Gibbon Nature Reserve, Guangxi, China. We did not find that groups sang more frequently than expected at the periphery of their home ranges, which does not support the boundary defense hypothesis. Instead, groups sang from the core area or irrespective of locations within an established territory, supporting the hypothesis that they advertise continuous occupancy of territories through regular singing. Singing locations were at significantly higher elevation than non-singing locations for both groups in the two study periods, supporting the hypothesis that cao vit gibbons choose singing locations to maximize sound transmission and minimize signal attenuation in karst forest. Thus, although the sample size is small, our study suggests that gibbons display flexibility in their choice of singing sites in different environments to ensure they can defend their territory. [ABSTRACT FROM AUTHOR]

Primates living in high-latitude habitats are expected to employ feeding strategies appropriate to harsh environments characterized by strong seasonality in temperature and food resources. We studied diet, feeding behavior, and seasonal changes in food availability in wild Taihangshan macaques (Macaca mulatta tcheliensis) living in a northern montane habitat (800–1700 m) in Mt. Tiantanshan area, Jiyuan, north China. From June 2016 to May 2017, we collected data on the diet and feeding behavior of one group of macaques and measured food availability in twenty 20-m × 20-m plots in their home range. We identified 105 plant species eaten by the macaques, belonging to 44 genera and 30 families. The macaques' diet comprised nine major categories: seeds (45.9% ± 31.2%), tree leaves (23.3% ± 27.2%), herbaceous leaves (15.3% ± 11.0%), young bark (5.6% ± 10.1%), fruits (2.5% ± 3.4%), buds (2.4% ± 5.5%), flowers (1.9% ± 3.4%), herb roots (1.8% ± 2.2%), and young twigs (1.5% ± 1.9%). We found significant seasonal variation in the dietary proportion of leaves, seeds, herbaceous roots, and young twigs. The proportion of each food type consumed was positively correlated with its availability in the habitat, but preferred food types varied monthly and seasonally. Seeds were the most preferred food, while tree leaves and herbaceous leaves served as fallback foods when seed availability was low. Faced with the scarcity of food resources and strongly seasonal changes in their high-latitude habitat, Taihangshan macaques employed a seed- and leaf-based feeding strategy, reflecting their ecological and evolutionary adaptation to temperate forests. [ABSTRACT FROM AUTHOR]

Clarifying the scientific identity of ancient biological names in historical archives is essential to understand traditional knowledge and literary metaphors of animals in human culture. Adopting a cross-disciplinary (Primatology, Linguistics, Historiography, Historical Sociology) analysis, we developed a theoretical framework for studies of the scientific identity of Chinese primate traditional names (e.g., Yuan 猿) throughout history, and interpret the historical evolution of the understanding of the Chinese word Yuan. Presently, the Chinese generally understand Yuan to be a gibbon (or "ape" in a broader sense), but this statement has many contradictions with the understanding of the word in relevant historical discourse. We review and comment on key evidence to support the traditional understanding of Yuan as a gibbon (Hylobatidae) and clarify the historical and current thought concerning Yuan. We find that the referent of the word Yuan has changed from "François' langur (Trachypithecus francoisi) with long limbs" to the "long-armed ape or gibbon" known today through two major changes in the idea of Yuan. One transformation in the conceptualization of Yuan took place during the Tang-Song period, with the other beginning at the end of the nineteenth century and ending in the 1950s. An interaction between the conceptualization of animals and power (e.g., political opportunity; cultural movement toward learning western sciences in the semi-colonial era) played an important role in these two diachronic changes to the idea of Yuan. In contrast to the clear linear relation between a species and its Latin name, our study indicates that one traditional name can represent varying animal species in China. Our findings exemplify the implications of the sociocultural and linguistic basis for the species identification of primate names found in historical discourse for historical zoogeography, our understanding of the intricate cultural and religious connections between humans and primates, and efforts to decolonize primatology. [ABSTRACT FROM AUTHOR]

Although selecting advantageous sleeping sites is crucial for nonhuman primates, the extent to which different factors contribute to their selection remains largely unknown for many species. We investigated hypotheses relating to predator avoidance, food access, and thermoregulation to explain the sleeping behavior of Bale monkeys (Chlorocebus djamdjamensis) occupying a degraded fragmented forest, Kokosa, in the southern Ethiopian Highlands. We found that the study group reused 11 out of 20 sleeping sites used during the 42 study days over a 6-month period. Sleeping sites were usually close to the last feeding trees of the day (mean distance =15.2 m) and/or the first feeding trees of the next morning (mean distance = 13.5 m). This may reflect an attempt to maximize feeding efficiency and reduce travel costs. Compared to the mean trees in the study area, sleeping trees were significantly shorter. Bale monkeys selected sleeping places in trees with high foliage density above and below them, lending support to the hypothesis that they select sleeping places that can conceal them from predators and at the same time offer shelter from cold weather. The monkeys also frequently huddled at night. Our results suggest that predator avoidance, access to food resources, and thermoregulation all likely influence the selection of sleeping sites by Bale monkeys. [ABSTRACT FROM AUTHOR]

To understand how animals select resources we need to analyze selection at different spatial levels or scales in the habitat. We investigated which physical characteristics of trees (dimensions and structure, e.g., height, trunk diameter, number of branches) determined nesting selection by chimpanzees (Pan troglodytes) on two different spatial scales: individual nesting trees and nesting sites. We also examined whether individual tree selection explained the landscape pattern of nesting site selection. We compared the physical characteristics of actual (N = 132) and potential (N = 242) nesting trees in nesting sites (in 15 plots of 25 m × 25 m) and of all trees in actual and potential nesting sites (N = 763 in 30 plots of 25 m × 25 m). We collected data in May and June 2003 in Issa, a dry and open savanna habitat in Tanzania. Chimpanzees selected both the site they used for nesting in the landscape and the trees they used to build nests within a nesting site, demonstrating two levels of spatial selection in nesting. Site selection was stronger than individual tree selection. Tree height was the most important variable for both nesting site and tree selection in our study, suggesting that chimpanzees selected both safe sites and secure trees for sleeping. [ABSTRACT FROM AUTHOR]

Primates must select sleeping sites carefully to maximize fitness. In habitats with diminished quality and availability of resources, sleeping site selection becomes an even more crucial aspect of primate survival. We investigated sleeping site selection patterns in northern pigtailed macaques (Macaca leonina) living in a degraded habitat by testing the hypotheses of random selection, predation avoidance, and food proximity. We followed a group of northern pigtailed macaques in Sakaerat Biosphere Reserve, northeastern Thailand, over 14 months between February 2017 and October 2018. We identified 107 total sleeping sites and analyzed the forest structure at 50 sleeping sites and 50 randomly selected available sites. While the rate of reuse was low and random (N = 15), with sleeping sites characterized by a low availability of large and tall trees, the selection pattern was not random, with sleeping sites occurring more often in familiar areas (i.e., high site fidelity), and those with a greater number of stems and a higher canopy. These sleeping site characteristics were likely selected to decrease detection by predators and facilitate macaque escape in case of attack, supporting the predator avoidance hypothesis. However, food proximity also played a key role in sleeping site selection in this degraded habitat. Macaques often slept within, or close to, their first/last feeding site and selected their sleeping sites following food distribution, presumably to maximize energy intake. Our results present a new impact of habitat degradation on sleeping site selection in large primate groups: the use of a high number sleeping sites in order to cope with low availability and scattered distribution of fruit resources. [ABSTRACT FROM AUTHOR]

When preferred foods are scarce, one strategy employed by primates is to switch to an alternative food item of lower quality or preferability, i.e., a fallback food. In the montane rainforest of Nyungwe National Park in southwestern Rwanda, Rwenzori black-and-white colobus (Colobus angolensis ruwenzorii) (hereafter Rwenzori colobus) form a supergroup comprising hundreds of individuals. Over 13 mo we investigated how this supergroup uses resources in periods of resource abundance vs. periods of resource scarcity. Based on 5603 feeding records we first identified preferred foods and then identified fallback foods as those food categories or species whose consumption increases when preferred foods, or preferred food categories, are less available. When the availability of 19 preferred food items was low, fruticose lichens (Usnea sp.) contributed >50% of the monthly diet for the Rwenzori colobus. Moreover, consumption of lichens was significantly negatively related to the availability of preferred foods. Fruticose lichens can therefore be considered a fallback food for Rwenzori colobus that sustains the supergroup during periods of reduced food availability. This result, in combination with previous findings that mature foliage in Nyungwe is of high quality and does not elicit feeding competition, points to the importance of resources in facilitating supergroup formation. However, several other montane forests in Eastern Africa also harbor fruticose lichens and yet support only small groups of Angolan colobus, suggesting that additional factors such as sufficient forest size and limited fragmentation and hunting pressure by humans are required for supergroups to form. [ABSTRACT FROM AUTHOR]

Examining the diets of primate populations inhabiting different habitat types could be useful in understanding local adaptation and divergence between these populations. In Cameroon, the Nigeria–Cameroon chimpanzee (Pan troglodytes ellioti) is subdivided into two genetically distinct populations that occupy different habitat types; one occurs in forests to the west and the other in a forest–woodland–savanna mosaic (ecotone) in the center of the country. We used macroscopic fecal sample assessment to investigate dietary differences in relation to monthly fruit availability among P. t. ellioti communities in both habitat types: at Ebo Forest (rainforest) and Mbam and Djerem National Park (ecotone). We collected data simultaneously across three sites: Bekob and Njuma (rainforest) and Ganga (ecotone) from January 2016 to December 2017. In the dry season, fruits were the most important dietary component at Bekob and Njuma, while nonfruit plant material (leaves, pith, and bark) were most important at Ganga. In the wet season, the proportion of fruits in the diet was greatest at Ganga, while nonfruit plant material dominated chimpanzee diets at Bekob and Njuma. Chimpanzees at Bekob ate more fruits from introduced and secondary forest plant species than those at Njuma and Ganga, especially during periods of fruit scarcity. Animal consumption was higher at Ganga and was inversely associated with fruit consumption. These observations link habitat diversity to differences in feeding ecology among genetically distinct populations of P. t. ellioti. We speculate that dietary differences reflect broader socioecological variation between these populations, and collectively, that these factors promote intraspecific divergence. [ABSTRACT FROM AUTHOR]

The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body stability, risk of parasite infection, access to food, and range defense in the sleeping behavior of black-and-gold howler monkeys (Alouatta caraya) in northern Argentina. We collected data for 4 groups over 12 mo (198 study days). Black-and-gold howlers used 12 of 36 available tree species as sleeping trees. In comparison to the available trees, sleeping trees had a larger diameter at breast height, greater total height, and greater height of the lowest branch. Monkeys used large branches to sleep more frequently than small branches. Our results suggest that howlers avoided using the same sleeping tree on consecutive nights. At sleeping trees, individuals descended to lower branches to defecate. Sleeping sites were close to morning feeding sites. More sleeping sites were located in areas of range overlap between groups (75%) than in exclusive-use areas (25%), and sleeping sites located in overlapping areas were used more frequently when neighboring groups were nearby than when they were far away. Our results suggest that body stability, parasite avoidance, access to food, and range defense all affect the selection of sleeping sites. [ABSTRACT FROM AUTHOR]

Space use patterns are the result of complex interactions between individuals and their environment. Although competition with conspecifics, the distribution and availability of food resources and climatic conditions may all influence space use by primates, these factors are usually addressed separately. Studies that integrate social, ecological, and physical factors have the potential to improve our understanding of variation in the spatial behavior of primates. We studied two groups of mantled howler monkeys (Alouatta palliata) in Los Tuxtlas, Mexico, to explore how intergroup competition, food availability, and ambient temperature influenced their use of space over 15 months. Loud calls produced by neighboring groups were a determining factor in the variation in the area used per month, daily ranging distance, and travel rate. Food availability did not influence any aspect of spatial behavior, but the distribution of feeding trees affected travel rate. Ambient temperature influenced the frequency and speed of travel. These results suggest that the spatial behavior of howler monkeys is influenced by social (intergroup competition), ecological (food distribution), and physical (ambient temperature) factors, and that the specific effects of these factors vary among measures of space use. [ABSTRACT FROM AUTHOR]

Sleep is an important and time-consuming activity, during which animals may be particularly vulnerable. Selecting a suitable sleeping site is therefore essential for an individual's fitness. Here we test the importance of antipredator and thermoregulatory hypotheses for the sleeping site preference of a nocturnal primate, the Northern lesser galago (Galago senegalensis), in Northern Tanzania. During June to August of 2015 and 2016 we conducted daily surveys of sleeping sites to record the number of galagos and their location within the sleeping tree, and used focal follows to record when galagos reached and left sleeping sites. We collected vegetation data for sleeping sites (N = 47) and matched controls, and placed data loggers in sleeping (N = 14) and control locations to compare temperature and humidity. Sleeping group sizes were similar to that of G. senegalensis in The Gambia, and the mean proportion of visits in which galagos were present at each site was 27 ± SD 25%. Galagos slept on branches (N = 29), nests (N = 6), palm leaves (N = 6), and in tree cavities (N = 1). Palm leaves have not been previously recorded as regular sleeping sites for galagos and were overrepresented relative to their occurrence in the habitat. Random forest classification analysis revealed that galagos sleep in areas with greater canopy cover and connectivity, greater mid-level vegetation cover, higher tree density, and a greater number of Acacia trees. Sleeping locations had significantly lower mean temperatures but greater mean humidity than control locations. Our findings support predator avoidance and thermoregulation as drivers of nesting behavior. In particular, the characteristics of galago sleeping sites correspond well to those expected for protection from aerial predators, while those related to protection from terrestrial predators seem to play a minor role. [ABSTRACT FROM AUTHOR]

Most pair-living primate species engage in duets, wherein males and females produce coordinated vocalizations. Previous analyses of male gibbon contributions to the duet have shown that calls are individually distinct. Here we investigate variation in the temporal and spectral parameters in the male contribution to the duet, also known as the coda, of wild, nonhabituated male Müller’s Bornean gibbons (Hylobates muelleri), recorded both opportunistically and as a response to playbacks at the Stability of Altered Forest Ecosystems site in Sabah, Malaysia. We used linear discriminant function analysis to estimate the intra- and interindividual variation in 13 spectral and temporal parameters of the vocalizations (N = 337) of 31 male gibbons. To further understand how call features vary within and between individuals we used a multivariate, variance components model to investigate how variance in features was partitioned at these two levels. We could identify males with a 66% accuracy using leave-one-out cross-validation, a relatively low score compared to female Müller’s Bornean gibbons and males of other species. We found that for some features (such as maximum frequency of the notes) most of the variance occurred between males, but for others (specifically total duration of the call and duration of rest in between notes) most of the variance occurred within a single male. Overall, male Müller’s Bornean gibbon coda vocalizations showed greater variability relative to their female counterparts, raising questions about potential differences in the function of the male and female contributions to the duet in Müller’s Bornean gibbons and the gibbon taxon as a whole. [ABSTRACT FROM AUTHOR]

Primates are among the most important seed dispersers in the habitats they occupy. Understanding the extent of, and gaps in, our knowledge of seed dispersal by Asian primates is essential, because many of these primates are extremely vulnerable to anthropogenic disturbance. In this review, I show how initial studies focused on the role of individual species in seed dispersal have expanded more recently to consider their role in the wider frugivore community. There are five functional groups of primate seed dispersers in Asia; most of our information comes from the (usually) highly frugivorous macaques and gibbons, while our understanding of the roles played by orangutans and, especially, colobines and lorises remains rudimentary. Preliminary community-wide studies suggest a pivotal role for gibbons and macaques in frugivore communities, with higher dispersal overlap with other mammals than with birds. The gaps in our knowledge are plentiful, however, including understanding fruit selection in detail, determining how seed dispersal roles might change across different habitats, evaluating the balance between mutualisms and antagonisms in orangutans and macaques, describing postdispersal processes, and documenting how habitats are impacted by changes in primate abundance and behavior. [ABSTRACT FROM AUTHOR]