Primates最新文献

Gibbons, a type of lesser ape, are brachiators but also walk bipedally and without forelimb assistance, not only on the ground but also on tree branches. The arboreal bipedal walking strategy of the gibbons has been studied in previous studies in relation to two-dimensional (2D) kinematic analysis. However, because tree branches and the ground differ greatly in width, leading to a constrained foot contact point on the tree branches, gibbons must adjust their 3D joint motions of trunk and hindlimb on the tree branches. Furthermore, these motor adjustments could help minimize the center of mass (CoM) mediolateral displacement. This study investigated the kinematic adjustment mechanism necessary to enable a gibbon to walk bipedally on an arboreal-like substrate using 3D measurements. Trials were recorded with eight video cameras that were placed around the substrate. The CoM position on the body, the Cardan angles of the hindlimb joints and trunk, and spatiotemporal parameters were calculated. Asymmetry of thorax, pelvis, trunk, and left and right hindlimb joint motion was observed in the pole and flat conditions. In the pole condition, the narrower step width and the smaller range of motion of the mediolateral CoM displacement were observed with increased hip adduction and knee eversion angles. These kinematic adjustments might place the knee and foot directly under the body during the single support phase, producing a reduced step width and the amount of the mediolateral CoM displacement of a gibbon.

Industrial expansion has brought humans and wildlife into closer contact, and added novel, complex dimensions to human-wildlife relationships. The seven great apes (chimpanzee, Bornean orangutan, Sumatran orangutan, Tapanuli orangutan, Eastern gorilla, Western gorilla, bonobo), the closest extant relatives to humans, have experienced substantial population declines resulting from anthropogenic activities. The effect of human activity on great ape behavioural ecology is therefore an emerging field of inquiry in primatology which has historically been minimally considered. This review explores how wild great apes respond behaviourally to human activities and environmental changes, synthesizing current knowledge and addressing potential outcomes and risks. Using precise search criteria, we found 96 studies documenting changes in great ape behaviour in response to human activity, and despite their broad geographic distribution, we found common patterns and responses across species to increasing human influence. Literature documented shifts in existing behaviour (57), the generation of novel behaviours (53) or reported both (15). Forty-three studies (45%) included direct (23) or indirect (20) assessment of the consequences of these behaviours. Only one study modelled a widespread loss of existing behaviours. The majority of studies included chimpanzees (67), followed by orangutans (19) and gorillas (19), and only 2 included bonobos. We found that the most frequently documented drivers of behavioural responses to anthropogenic activity were wide-scale land-use conversions in ape habitats. In response, apes have adopted crop foraging, and altered nesting behaviour, range use, and social strategies. While these responses appear to allow survival in the immediate sense, they may expose individuals to more risks in the long term. Analysis revealed that under many contexts changing great ape behaviour is putting strain on the human-ape relationship, resulting in injury, harassment, and even the killing of apes. We found examples of tolerant relationships between humans and apes shifting towards conflict, potentially worsening the conservation crisis and inviting inquiry into tolerance thresholds among human communities. We emphasize the importance of community-engaged strategies for reducing competition over resources and conclude that great ape behavioural responses to human activity must be interpreted through a locally specific lens.

The use of complex technologies by humans (Homo sapiens) and their ancestors is a key feature of our evolution, marked by the appearance of stone tools 3.3-million years ago. These technologies reflect cognitive complexity and an advanced understanding of materials and mechanics. Studying current primates, especially those that use stones, offers insights into the evolution of human behaviours. In particular, stone manipulation by macaques suggests that some complex behaviours in humans, such as creation of cutting and biface tools, could have emerged unintentionally. The Japanese macaques (Macaca fuscata) of Shodoshima were observed to leave marks on the ground with stones and chalk. By analysing this manipulation of stones, I suggest that drawing in humans could have appeared unintentionally; these unintentional origins of mark-making behaviours may represent early precursors to human drawing.

Huddling behaviour is present in many animal species. This behaviour involves maintaining close physical contact with conspecifics to minimise heat loss and, in general, reduce energy expenditure. Additionally, this behaviour also facilitates complex social interactions within a population. In Japanese macaques, this behaviour is observed in many populations across Japan, including Shodoshima, where huddling clusters can reach up to 100 individuals in winter. Based on several studies on this species, it appears that huddling, or sarudango in Japanese, is influenced by both meteorological factors and social relationships between individuals. The objective of this study is to understand the determinants that drive the expression (presence or absence) and the organisation (number of individuals and identities) of huddling clusters. Two hypotheses were formulated. The first hypothesis posits that the formation and variations in the size and number of clusters are influenced by meteorological factors, while the second hypothesis suggests that the number and position of individuals within a cluster are related to existing relationships between individuals. To test these, data on the number, size, and individuals composing a cluster were collected, allowing building huddling social networks. Simultaneously, meteorological measurements were taken, along with observations on dominance and grooming interactions between individuals. This allowed us to create several statistical models and social networks for comparison. Our results suggest that the probability for observing huddling is mainly related to solar radiation energy, while variations in number and size could be explained by temperature. Moreover, the organisation within a cluster is not random but reflects relationships between individuals. The ones sharing more grooming and having similar dominance ranks have more probabilities to be in the same huddling cluster.

Food supplementation by humans in peri-urban and urban landscapes can lead to excessive intake of energy and certain macronutrients, and affect animal health. In this study, we evaluated the influence of food supplementation on urinary health indicators in brown howler monkeys (Alouatta guariba) by comparing supplemented and non-supplemented free-ranging peri-urban groups. We also evaluated the effect of sex, day shift, and season of sampling. Between August 2021 and August 2022, we non-invasively collected 61 samples (43 from females and 18 from males) from adult individuals (N = 10) in three supplemented groups and 56 samples (25 from females and 31 from males) from adults (N = 7) in three non-supplemented groups. The supplements, mostly raw foods (e.g., fruits, vegetables, and tubers) and bread, represented 18% of the total fresh mass ingested by the supplemented groups. We assessed pH, density, and the presence of eight urine components (glucose, bilirubin, ketones, protein, urobilinogen, nitrite, blood, and leukocytes) using reagent urine strips. Season of sampling predicted urine density (mean = 1.022), while both season and day shift predicted pH (mean = 6.5). The occurrence of supplementation was a weak predictor of these parameters. Finally, we detected leukocytes in 21% of the 117 samples. We did not identify any visible signs of disease in any individual throughout the study and found no clinical changes in urine under the conditions studied. We urge validation of the results with urine strips to facilitate monitoring of the health of howler monkeys living in anthropogenic landscapes in the presence or absence of dietary supplementation.

Knowledge about changes in wildlife populations over time is essential for making informed decisions regarding their conservation. We evaluated the influence of distinct habitat factors on the occupancy of Olalla's titi monkey (Plecturocebus olallae), a Critically Endangered primate endemic to Bolivia. We assessed the presence of titi monkey groups using the playback technique, employing point counts in 582 quadrants of approximately 6.25 hectares. Utilizing single-species and single-season occupancy models, we estimated an occupancy (ψ) of 0.21 and found that the presence of P. olallae groups was positively related to heterogenous plant composition forests which indicates they may be more likely to occur in areas of high floristic diversity. We also found that groups of this already range restricted species do not occur in all the forest coverage within their distributional range. This complements previous considerations regarding the habitat in which P. olallae occurs based on its natural history knowledge and highlights the limited suitable habitat for this species. From our sampling effort, we calculated a power of 81% to detect a population change of 30%, showing the potential of occupancy modeling for population monitoring of P. olallae. Thus, we provide an information baseline that will be useful in further population monitoring actions for the conservation of these endemic Bolivian titi monkeys.

Because of the universal decline in biodiversity, it is important to map and assess the populations of the endangered species, especially those endemic to small regions, in their remaining wild habitats. With the main focus on the distribution and habitat suitability of the endangered lion-tailed macaque, Macaca silenus, we carried out a survey on primates in the Kodagu region of the Western Ghats, an area not properly explored earlier. The survey trails covered a length of 523 km. We encountered 185 groups of primates including 112, 12, 43 and 18 groups of bonnet macaques, M. radiata, lion-tailed macaques, black-footed gray langurs, Semnopithecus hypoleucos and Nilgiri langurs, S. johnii, respectively. The Brahmagiri Hills harbored the northernmost group of Nilgiri langurs and the southernmost group of black-footed gray langurs. Habitat suitability analysis revealed that the distribution of bonnet macaques and black-footed gray langurs was associated with a large number of environmental factors whereas only a few factors each influenced the distribution of other primate species. When considering the whole landscape spanning over 1295 km², black-footed gray langurs (961 km²), bonnet macaques (910 km²) and lion-tailed macaques (779 km²) had more suitable habitats than Nilgiri langurs (258 km²). The reserved forests between two Wildlife Sanctuaries covered an area of 311 km² where 282 km², 228 km², 272 km², and 140 km² areas were found to be suitable for lion-tailed macaques, bonnet macaques, black-footed gray langurs and Nilgiri langurs, respectively. We recommend these reserved forests to be included in the protected area network. The study brings out the Kodagu region to be a potential conservation area not only for the lion-tailed macaques but also for other primate species.

Social support, via investment in relationships of importance with others, is often emphasized as a pathway towards mediating stress. The effectiveness of social support, however, can be altered by personality differences, but the physiological consequences of such covariation are still poorly explored. How do individual differences in the functioning of the stress response system mediate access to, and use of, social support? To examine this dynamic, we investigated glucocorticoids as a biomarker of energetic activation that may also be activated by chronic psychosocial stress. For this purpose, we studied a wild anthropoid primate, i.e. the olive baboon (Papio anubis), for 17 months, in Laikipia District, Kenya. We measured biomarkers of energetic activation, i.e., fecal glucocorticoid metabolites (fGCms), to address whether individual differences in stress coping and social support were associated with variation in hormone levels across a period from 2018 to 2019. We found evidence for an association between social support and fGCm concentrations. This association had a discernable interaction between sex and social support: we found a negative association in male baboons, relative to females-who did not have a pronounced effect. Our findings emphasize the importance of social support in male baboons. The cost of not having diverse bonds, has been downplayed in male baboons.

Infant adoption is an association that occurs between an adult individual and a dependent infant and occurs most often when lactating females care for a nutritionally dependent infant that is not her offspring. Adult females are often involved in adoption; while, direct infant care by males occurs in less than 5% of all mammalian species. We report the first record of adoption by wild male adults of Alouatta caraya, a platyrrhine primate species that does not typically participate in parental care. We observed two independent cases of adoption, in two different groups (G1, G2) at the Corrientes Biological Station, Argentina. After the death of two adult females with dependent infants, one adult male adopted an orphan in each group. We recorded the activity of the adoptive males and the two infants. During this period, adoptive males expressed parental care behaviors toward infants. However, after 38 days in G1 and 53 days in G2, both infants died. Based on our continuous monitoring of study groups, we suggest that adoptive males are the biological parents of the orphaned infants. As such, kin selection may explain the care of the infants. However, another explanation could be group familiarity, which refers to the social bonds and cohesion that develop among individuals within a group, even if they are not genetically related. An adult male, although not genetically related to the infants, may take care of them due to the cohesion and relationships established within the group during his period of residence. The study of these rare parental behaviors taken by A. caraya adult males provide insights into the knowledge of group social cohesion and structure.