Influence of food availability and climate on behavior patterns of western black crested gibbons (Nomascus concolor) at Mt. Wuliang, Yunnan, China

Sympatric primate seed dispersers and predators jointly contribute to plant diversity in a subtropical forest

Mutualistic and antagonistic plant-animal interactions differentially contribute to the maintenance of species diversity in ecological communities. Although both seed dispersal and predation by fruit-eating animals are recognized as important drivers of plant population dynamics, the mechanisms underlying how seed dispersers and predators jointly affect plant diversity remain largely unexplored. Based on mediating roles of seed size and species abundance, we investigated the effects of seed dispersal and predation by two sympatric primates (Nomascus concolor and Trachypithecus crepusculus) on local plant recruitment in a subtropical forest of China. Over a 26 month period, we confirmed that these primates were functionally distinct: gibbons were legitimate seed dispersers who dispersed seeds of 44 plant species, while langurs were primarily seed predators who destroyed seeds of 48 plant species. Gibbons dispersed medium-seeded species more effectively than small- and large-seeded species, and dispersed more seeds of rare species than common and dominant species. Langurs showed a similar predation rate across different sizes of seeds, but destroyed a large number of seeds from common species. Due to gut passage effects, gibbons significantly shortened the duration of seed germination for 58% of the dispersed species; however, for 54% of species, seed germination rates were reduced significantly. Our study underlined the contrasting contributions of two primate species to local plant recruitment processes. By dispersing rare species and destroying the seeds of common species, both primates might jointly maintain plant species diversity. To maintain healthy ecosystems, the conservation of mammals that play critical functional roles needs to receive further attention.

Effects of food availability and climate on the activity budget of Shortridge's langur (Trachypithecus shortridgei) in the Drung Valley, Gaoligong Mountains, China

Food availability and climate represent environmental factors that affect species' social behavior, ranging patterns, diet, and activity budget. From August 2012 to September 2013, we examined the effects of seasonal changes in food availability, temperature, and rainfall on the diet and behavioral ecology of Shortridge's langur (Trachypithecus shortridgei) an Endangered primate species inhabiting moist evergreen broadleaf forests in the Eastern Himalayas. Our field site represents the northernmost latitudinal distribution of this species. Data were collected using scan sampling at 10 min intervals, and analyzed based on generalized linear models. The results indicate that the langurs experienced two feeding peaks (9:00 and 17:00) and two traveling peaks (10:00 and 19:00) during each day. Periods of rest, mainly occurred between 10:00 and 13:00, and overnight. Feeding accounted for 38.5% of the daily activity budget, followed by resting (35%), traveling (24.5%), and socializing (2%). During periods when young leaves were most available, the langurs increased feeding time on young leaves (35% vs. 4%). During periods of maximum fruit availability, the langurs decreased total time spent feeding (36.6% vs. 40.4%), devoted more time to traveling (28.1% vs. 21%), and increased time spent consuming fruit (49.1% vs. 11.8%). During the winter, the langurs increased their consumption of mature leaves (44.5%) and reduced time spent traveling (20.2% vs. 25.4%). Overall, time spent resting was greatest in the spring (47.5%), time spent feeding was greatest during the summer (51.1%), and time spent in traveling was greatest in the autumn (33.2%). The frequency of social interactions remained relatively constant throughout the year. Foraging effort was greatest in the summer, when fruits dominated the diet. Like other species of temperate langurs, T. shortridgei devoted less time to resting, more time to feeding, and was characterized by a greater year-round foraging effort than tropical/subtropical langurs.

Diet, food availability, and climatic factors drive ranging behavior in white-headed langurs in the limestone forests of Guangxi, southwest China

Changes in abiotic and biotic factors can affect the efficiency of biological systems in animals, forcing them to adjust their behaviors in response to daily and seasonal variations. From September 2016 to August 2017, we collected ranging behavior data on four groups of white-headed langurs ( Trachypithecus leucocephalus) in the Guangxi Chongzuo White-Headed Langur National Nature Reserve, Guangxi, southwest China. We simultaneously analyzed how multiple ecological factors affect langur ranging behavior, which should facilitate our understanding of the potential mechanisms underlying their adaptation to limestone habitats. Results showed that langur ranging behavior was significantly affected by diet composition, food availability, and climatic factors. Specifically, moving time and daily path length increased with the increase in dietary diversity. Furthermore, moving time and daily path length were positively associated with the availability of fruit and relative humidity of the forest, and moderately associated with temperature and relative humidity of bare rock. Our study demonstrated that langurs maintain stable moving and feeding times and exhibit a short daily travel distance, likely adopting an energy-conserving behavioral strategy in response to food shortages and high temperatures in the fragmented karst forest. These results highlight the importance of food availability and temperature in shaping the ranging behavior of these karst-dwelling primates.

The human-primate interface in the New Normal: Challenges and opportunities for primatologists in the COVID-19 era and beyond

The emergence of SARS-CoV-2 in late 2019 and human responses to the resulting COVID-19 pandemic in early 2020 have rapidly changed many aspects of human behavior, including our interactions with wildlife. In this commentary, we identify challenges and opportunities at human-primate interfaces in light of COVID-19, focusing on examples from Asia, and make recommendations for researchers working with wild primates to reduce zoonosis risk and leverage research opportunities. First, we briefly review the evidence for zoonotic origins of SARS-CoV-2 and discuss risks of zoonosis at the human-primate interface. We then identify challenges that the pandemic has caused for primates, including reduced nutrition, increased intraspecific competition, and increased poaching risk, as well as challenges facing primatologists, including lost research opportunities. Subsequently, we highlight opportunities arising from pandemic-related lockdowns and public health messaging, including opportunities to reduce the intensity of problematic human-primate interfaces, opportunities to reduce the risk of zoonosis between humans and primates, opportunities to reduce legal and illegal trade in primates, new opportunities for research on human-primate interfaces, and opportunities for community education. Finally, we recommend specific actions that primatologists should take to reduce contact and aggression between humans and primates, to reduce demand for primates as pets, to reduce risks of zoonosis in the context of field research, and to improve understanding of human-primate interfaces. Reducing the risk of zoonosis and promoting the well-being of humans and primates at our interfaces will require substantial changes from "business as usual." We encourage primatologists to help lead the way.