American Journal of Primatology最新文献

The lack of knowledge regarding the basic ecological traits of an endangered species may lead to traps in habitat restoration efforts. Understanding the ranging ecology of endangered species is essential in avoiding these traps. The Hainan gibbon (Nomascus hainanus), the world's rarest primate, reportedly takes refuge in suboptimal montane habitats and occupies an abnormally large home range, resulting in suggestions for enhancing montane habitat quality with high priority. However, these conservation suggestions and actions are not based on solid science. For the first time, we habituated two groups of Hainan gibbon, and studied their ranging ecology over a year from January to December 2022. We found that the average home range size of these groups was 164.5 ± 70.6 ha (95% KDE-href) and 155.2 ± 71.1 ha (95% MCP), which is comparable to other Nomascus gibbons and represents an adaptive trait in response to their heterogeneous habitat. Furthermore, gibbons have shown a preference for higher-altitude habitats between 800 and 1100 m, where food is more abundant than in low-altitude habitats. Our findings, combined with the evidence of favorable food conditions and short interbirth intervals of the Hainan gibbon, indicate that montane habitats meet gibbons' life-history requirements and are suitable for them. The idea that “montane habitat is suboptimal” is a cognitive trap. Given the Hainan gibbons' isolated habitat is approaching saturation, we suggest prioritizing ecological corridor construction to enable gibbons to rapidly gain access to other suitable montane forests.

Cao vit gibbon (Nomascus nasutus) is one of the world's 25 most endangered primate species, with only one population of 11 groups living in a small karst forest patch along the China–Vietnam international border. Assisted habitat regeneration is underway in both China and Vietnam to conserve the species. However, the lack of crucial information on habitat use and habitat preferences of these gibbons could severely compromise the conservation outcomes. To understand gibbon habitat use patterns and guide ongoing habitat restoration, we studied the ranging behavior of two cao vit gibbon groups in Bangliang Gibbon Nature Reserve, Guangxi, China. We established vegetation plots within gibbon's habitat along the altitudinal gradient. Then quantified food distribution in different altitudinal ranges. Both groups avoided using areas above 800 m, but preferred lower areas, and they spent more time feeding in low-altitude areas compared to high-altitude areas. Our analysis revealed that the altitudinal ranging pattern was affected by both food distribution and temperature. The gibbons preferred altitudes that provided more food for their diet, and their selectivity for lower altitudes increased as temperatures dropped while they adopted an energy-conserving strategy during cold seasons. Our results suggested that gibbons prefer habitats at lower altitudes, which serve as important feeding sites and provide refuges during cold exposure. Therefore, we strongly propose prioritizing reforestation in areas below 750 m by planting important food species.

Loud calls are critical for primate intergroup communication, influencing resource defense, territorial boundaries, and conflict management. This study examined the interplay of familiarity and numeric odds in shaping the behavioral and hormonal responses of male mantled howler monkeys (Alouatta palliata) to simulated intruder calls. Using playback experiments, we tested whether responses were consistent with “dear enemy” dynamics, which predict stronger responses to unfamiliar intruders, or “nasty neighbor” dynamics, which predict stronger responses to familiar intruders. Additionally, we assessed the influence of numeric odds, hypothesizing stronger responses under favorable conditions. Behavioral responses, including vocalization and approach latencies, were primarily influenced by numeric odds, with shorter latencies observed under favorable odds. Vocal duration, however, was longer when intruders were familiar, consistent with “nasty neighbor” dynamics. Hormonal responses, measured via fecal glucocorticoid and testosterone metabolites, increased in response to unfamiliar intruders, supporting “dear enemy” predictions. Interaction effects showed that familiarity modulated approach duration and latency when numeric odds were unfavorable. These findings reveal the distinct roles of numeric odds and familiarity in shaping immediate and prolonged responses to intruders. Numeric odds influenced engagement decisions, while familiarity was related to stress-related hormonal changes and vocal communication strategies. This study contributes to the understanding of intergroup dynamics by clarifying the role of competitive asymmetries and social relationships in conflict management. Future work incorporating multimodal cues and ecological variability will further elucidate the adaptive significance of these responses.

Ultrasound-guided intrauterine insemination (IUI) has been successfully employed in cynomolgus macaques, yet its effectiveness in large-scale, multi-age cohorts has not been fully explored. Here, we implemented IUI within large breeding colonies to boost pregnancy rates in cynomolgus macaques. Ovulation timing was estimated by monitoring menstrual bleeding, after which IUI was performed. We then compared single menstrual cycle (SMC) pregnancy rates between IUI groups and harem-style mating groups. Our findings revealed that the overall pregnancy rate in the IUI group was significantly higher than in the harem-style breeding group across all ages. Notably, this advantage was mainly attributable to monkeys over 10 years old; in contrast, no significant difference was observed among 4–5-year-old and 6–10-year-old monkeys. Although pregnant females in the IUI group exhibited a higher birth rate compared to those in harem-style breeding, this difference was not statistically significant. Collectively, these results establish a basis for refining reproductive technologies in older cynomolgus macaque breeding programs and highlight potential improvements in managing large-scale colonies.

Behavioral and dietary flexibility allow primates to effectively exploit resources that fluctuate in time and space. Here we examined monthly variation in the diet and activity budget of a wild nonprovisioned group of Tibetan macaques inhabiting Mt. Huangshan, China. From October 2022 to September 2023, we recorded the behavior of a group of wild macaques and collected data on food availability, temperature, rainfall, and day length. We found that over a 12-month period, the Tibetan macaques fed on 109 plant species. The main food types consumed were fruits (54.5%), leaves (24.3%), seeds (7.7%), stems (6.5%), flowers (4.0%), and buds (2.5%). Tibetan macaques were found to target fruits as a main resource during months in which fruits were most abundant. During months when fruits were scarce, they increased their consumption of leaves, seeds, and stems. The top three plant species each month accounted for 70.7% of total feeding time indicating that their foraging effort focused on a small number of highly productive plant species each month. The Tibetan macaque daily activity budget was dominated by feeding (3.98 h or 33.7%) and resting (3.81 h or 32.8%), followed by traveling (2.40 h or 20.9%) and socializing (1.45 h or 12.6%). When time spent feeding on leaves increased, the Tibetan macaques experienced a significant increase in time spent resting and a significant decrease in time spent feeding. In addition, during the months of December and January, pine seeds were found to be an important food for Tibetan macaques. It is possible that increasing lipid consumption during the cold winter months serves to offset the additional costs of thermoregulation. Our results indicate that Tibetan macaques flexibly adjusted their diet and activity patterns in response to monthly variation in temperature, rainfall, and food availability across a range of forest types in east-central China.

The threat of disease transmission at the intersection of human-wildlife interfaces underscores the urgent need for detailed studies on the transmission of human-borne pathogens across species, especially among nonhuman primates in urban areas. This research focuses on the social and demographic determinants of Mycobacterium tuberculosis complex (MTBC) infection in free-ranging long-tailed macaques (Macaca fascicularis) in Thailand. Behavioral observations and noninvasive biological specimens (freshly defecated feces and rope-baited oral samples) were collected from 98 long-tailed macaques living in Wat Khao Thamon, southern Thailand, between August 2021 and February 2022. We detected the MTBC antigen using IS6110 nested-PCR method in 11 out of 98 monkeys (11.22%). Logistic GLMs revealed that the risk of MTBC acquisition was higher among macaques with frequent human-macaque interactions, whereas increased social grooming of conspecifics showed a nonsignificant trend toward reducing the risk. Our findings suggest that anthropogenic exposure increases the risk of MTBC infection among macaques, but this risk may be mitigated (socially buffered) by increased within-group affiliative interactions. More generally, the potential for increased disease prevalence in wildlife with frequent human interactions or reduced social buffering highlights the need to consider animal socio-demography when developing strategies to understand and prevent the transmission of diseases between humans and wildlife.