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Studying sleeping behavior can provide key information for understanding the ecology of a species. Antipredation is an important factor that affects primate sleeping behavior. We studied antipredation sleeping behavior in skywalker hoolock gibbons ( Hoolock tianxing). We studied one group (NA) and a solitary female (NB) at Nankang from July 2010 to September 2011, and another group (BB) at Banchang from May 2013 to December 2014 in Mt. Gaoligong, Yunnan, China. Over the study period, we recorded 67 sleeping trees for members of group NA over 92 days, 17 trees for the solitary female NB over 22 days, and 159 trees for members of group BB over 186 days. Skywalker hoolock gibbons at both sites rarely used the same tree on consecutive days ( N = 3 at both sites). They traveled fast to enter sleeping tree a mean of 160 ± SD 43 min before sunset at Nankang, and a mean of 192 ± SD 40 min before sunset at Banchang. They seldom (Nankang: 14%, N = 183 observations; Banchang: 25%, N = 548 observations) defecated in sleeping trees. They slept at sites with more tall and large trees and preferred to sleep on tall trees in the site. They slept on branches of small diameter and closer to tree tops. Our study suggests that antipredation plays an important role in skywalker hoolock gibbons' sleeping tree selection and sleeping behavior. In addition, our data suggest potential effects of habitat degradation on gibbons' sleeping behavior. Tall trees are especially important for gibbons in degraded forest and should be protected. [ABSTRACT FROM AUTHOR]

Gibbons (Hylobatidae) were widely distributed across much of China during recent centuries, but are now restricted to a few small areas of Hainan, Guangxi, and Yunnan provinces due to massive habitat loss and hunting. Six gibbon species have occurred recently in China. Two of them ( Hylobates lar and Nomascus leucogenys ) are now extinct; two others ( Nomascus nasutus and Nomascus hainanus ) each have only one small population with less than 30 individuals; Hoolock leuconedys has a small population of less than 200 individuals distributed in 17 locations; and even the most common species, Nomascus concolor , has populations containing only about 270 social groups (ca. 1200 individuals). Illegal hunting, forest fragmentation, small population size, limited habitat, and various other types of human disturbance still threaten remnant gibbon populations. Currently, all gibbon species are listed as Class One Protected Animals by Chinese law and about 85% of gibbon groups are protected within nature reserves. Several long-term monitoring and research programs have been established in order to better understand gibbon population dynamics, ecology, and behavioral adaptations to human disturbance, and habitat restoration and conservation education programs are underway. In order to ensure long-term survival of gibbons in China, expanding and establishing nature reserves, strengthening law enforcement, increasing conservation education, establishing captive breeding programs for reintroduction, recruiting new researchers and students, and international cooperation are suggested. If most of these activities can be achieved, Chinese gibbons may still have a future in the wild. [ABSTRACT FROM AUTHOR]

We describe a species of Hoolock gibbon (Primates: Hylobatidae) that is new to science from eastern Myanmar and southwestern China. The genus of hoolock gibbons comprises two previously described living species, the western ( Hoolock hoolock) and eastern hoolock ( H. leuconedys) gibbons, geographically isolated by the Chindwin River. We assessed the morphological and genetic characteristics of wild animals and museum specimens, and conducted multi-disciplinary analyses using mitochondrial genomic sequences, external morphology, and craniodental characters to evaluate the taxonomic status of the hoolock population in China. The results suggest that hoolocks distributed to the east of the Irrawaddy-Nmai Hka Rivers, which were previously assigned to H. leuconedys, are morphologically and genetically distinct from those to the west of the river, and should be recognized as a new species, the Gaoligong hoolock gibbon or skywalker hoolock gibbon ( H. tianxing sp. nov.). We consider that the new species should be categorized as Endangered under IUCN criteria. The discovery of the new species focuses attention on the need for improved conservation of small apes, many of which are in danger of extinction in southern China and Southeast Asia. [ABSTRACT FROM AUTHOR]

We conducted surveys to estimate the current population and distribution of the recently described Gaoligong hoolock gibbon (Hoolock tianxing) in Yunnan Gaoligongshan National Nature Reserve Tengchong Bureau (TC-GLGS). The reserve supports the northernmost known population of the species in China. A total of 17-20 gibbons in 6-7 family groups were recorded in TC-GLGS in a population census conducted in 2016. The mean group size was 2.8-2.9 individuals (range 2-4) with a population density of 0.18-0.21 groups/km2. All groups contained a single adult pair, and juveniles and/or infants were observed in all but two. Mean dawn time was 07:26 h during the survey, and vocalizations were concentrated in the first hour after dawn (57.9% of total song bouts), with an average song bout duration of 25.7 min (n = 19). Four other primate species occurred in sympatry with the gibbons in the study area, with Macaca arctoides and M. assamensis being the most abundant. TC-GLGS appears to support the single largest subpopulation of H. tianxing in China, but the population density was very low, despite the presence of large areas of healthy, closed-canopy forest, suggesting that the population may have been well below carrying capacity. The suppressed population size is a combined result of rampant hunting in the past, loss of lower elevation forest, and ongoing disturbance by cattle grazing in the remaining gibbon habitat. Long-term conservation challenges facing the Gaoligong hoolock gibbon in China include the prevention of poaching and disturbance, restoration of deforested areas <2,000 m asl, and the establishment of biological corridors between forest fragments. Translocation to areas contiguous with larger subpopulations should be considered for single groups in isolated forest fragments. [ABSTRACT FROM AUTHOR]

Many non-human primates produce species-specific loud calls to communicate within and between groups over long distances. Understanding these calling patterns can provide insights into how individuals modify their behavior in response to environmental variables as well as help to design efficient bioacoustic survey techniques. Eastern hoolock gibbons in Gaoligongshan inhabit the coldest habitat of all gibbon populations, but both conservation and research efforts on this population have been minimal. We studied singing patterns of two habituated and two unhabituated groups at two sites in Gaoligongshan between July 2010 and June 2015. We systematically collected data of their calls, and its relationship to temperature, group density, and hunting pressure over at least 1 year for each group. Our goal was to elucidate how these factors affect singing patterns of eastern hoolock gibbons. We found that adult pairs coordinated their singing to produce duet bouts that lasted for an average of 25.5 min. The singing rate (number of bouts/number on monitoring days*100%: 7.5-31.4%) was notably lower than other gibbon populations, presumably due to low group density (about 0.5 groups/km2) and prevalence of hunting at the study site. Cold temperature also affected gibbons' singing behavior. Our study groups called, on average, 2.5 hr after sunrise, probably foraging first in the early morning after long nights in this cold habitat delayed singing. Furthermore, mean temperatures in the morning (8:00-12:00 am) were higher on singing days than on non-singing days, and one group called less frequently when monthly mean temperature was below 10°C. Our findings indicate that both hunting pressure from humans and low temperatures suppress calling behavior in hoolock gibbons. Such information is critical in evaluating the use of duetting as a monitoring technique for this endangered gibbon species. Am. J. Primatol. 78:861-871, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Fossil hylobatids are rare, but are known from late Miocene and Pleistocene sites throughout East Asia. The best-known fossil hylobatid from the Pleistocene of China is a left mandibular fragment with M2-3 (AMNH 18534), recovered from a pit deposit near the village of Yanjinggou in Wanzhou District, Chongqing Province. Matthew and Granger described this specimen in 1923 as a new genus and species, Bunopithecus sericus. Establishing the age of Bunopithecus has proved difficult because the Yanjinggou collection represents a mixed fauna of different ages, but it likely comes from early or middle Pleistocene deposits. Although the Bunopithecus specimen has featured prominently in discussions of hylobatid evolution and nomenclature, its systematic status has never been satisfactorily resolved. The present study reexamines the taxonomic and phylogenetic relationships of Bunopithecus by carrying out a detailed comparative morphometric study of its lower molars in relation to a large sample of modern hylobatids. Our results show that differences in M2 and M3 discriminate extant hylobatids fairly well, at least at the generic level, and that AMNH 18534 is not attributable to Hylobates, Nomascus or Symphalangus. Support for a close relationship between Bunopithecus and Hoolock is more equivocal. In most multivariate analyses, Bunopithecus presents a unique morphological pattern that falls outside the range of variation of any hylobatid taxon, although its distance from the cluster represented by extant hoolocks is relatively small. Our results support the generic distinction of Bunopithecus, which most likely represents an extinct crown hylobatid, and one that may possibly represent the sister taxon to Hoolock. [ABSTRACT FROM AUTHOR]