Ecology and social system of northern gibbons living in cold seasonal forests.

Zhen-Hua Guan,Chang-Yong Ma,Peng-Fei Fan,Bei Huang,Wen-He Ning,Qing-Yong Ni,Han-Lan Fei,Xue-Long Jiang

doi:10.24272/j.issn.2095-8137.2018.045

Abstract

Gibbons in China represent the northernmost margin of present day gibbon species distribution (around N25). Compared to tropical habitats, northern gibbon habitats are characterized by low temperatures and remarkable seasonal variation in fruit abundance. How gibbons adapt to their cold and seasonal habitats and what ecological factors affect their sociality are key questions for understanding their ecology and social system evolution, the elucidation of which will contribute to the conservation of these special populations/species. According to preliminary short-term studies, northern gibbons consume more leaves and use larger home ranges than tropical gibbons. Interestingly, some Nomascus groups consist of more than one adult female. However, these preliminary results are not well understood or incorporated into current socio-ecological theories regarding gibbon species. To better understand northern gibbons, our team has systematically studied three habituated groups of Nomascus concolor, three groups of N. nasutus, and two habituated groups of Hoolock tianxing since 2002. In this paper, we stress the challenges facing gibbons living in northern habitats and summarize their behavioral adaptations to their harsh environments. We also describe the northern gibbon social system and discuss the potential relationships between their ecology and sociality. Finally, we highlight future research questions related to northern gibbons in China.

Highlights

Gibbons (Hylobatidae) are small apes that live in tropical and subtropical forests in southeastern Asia (Bartlett, 2011)
By the late 1980s, the remaining populations of three species had decreased to less than 40 individuals (N. hainanus: Liu et al, 1989; H. lar : Yang et al, 1987; N. leucogenys: Hu et al, 1990), and until recently N. nasutus was considered extinct in China (Tan, 1985)
When fruit is less accessible or absent, northern gibbons switch their diet to leaves and buds (Fan et al, 2009a, 2012, 2013), accounting for 83% of the N. concolor diet in March (Fan et al, 2009a), and increase their feeding time (Fan et al, 2008)

Summary

INTRODUCTION

Gibbons (Hylobatidae) are small apes that live in tropical and subtropical forests in southeastern Asia (Bartlett, 2011). The mated pair use a small home range of on average 42 hm, and actively defend 82% of the area (Bartlett, 2011) through direct intergroup conflicts (Bartlett, 2003) and regularly occurring loud morning songs (Geissmann, 2002; Mitani, 1985) Both sexes benefit from knowledge of this intensively-used territory and goal-directed foraging strategies (Brockelman, 2009). By the late 1980s, the remaining populations of three species had decreased to less than 40 individuals (N. hainanus: Liu et al, 1989; H. lar : Yang et al, 1987; N. leucogenys: Hu et al, 1990), and until recently N. nasutus was considered extinct in China (Tan, 1985). Our gibbonsrpeseecaricehss)it;esHarye laolsobmaatrekesd(o9n thsepmeacpi. es); Symphalangus (1 species)

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Findings

Standardized methods