Nomascus Concolor Jingdongensis Research Articles

The effective use of camera traps to document the northernmost distribution of the western black crested gibbon in China.

Gibbons represent a highly successful radiation of four genera and 20 species of Asian apes that, in response to recent habitat fragmentation and deforestation, are threatened with extinction. China has six species of gibbons, each of which is critically endangered. We present new biogeographical information on the distribution of the black crested gibbon (Nomascus concolor). Four subspecies of N. concolor have been described: three of them are present east of the Mekong River (Nomascus concolor jingdongensis, N. c. concolor and N. c. lu); and another is found west of the Mekong River (N. c. furvogaster). In addition, there has been speculation that gibbons exist in the Biluo Snow Mountains, between the Mekong and Salween basins. To clarify the biogeography of this species, from April 2011 to January 2012 and from January 2016 to September 2018, we conducted interviews with local villagers, completed line transect surveys, monitored gibbon calls, and placed 30 camera traps in the forest canopy. On October 30, 2016, we recorded gibbon's calls. On July 5, 2016, our camera traps obtained one image of a male gibbon, and on February 1 and 8, 2017, we captured two independent images of an adult female gibbon on Zhiben Mountains. Based on the black crest on the head, clearly visible in the photographs, the gibbons are N. c. furvogaster. Evidence from interviews and survey records indicate that N. c. furvogaster once was present in the Zhiben Mountains, at an altitude of between 2000 and 2700m. Between 1990 and 2000, some 6-7 groups still existed in Caojian, Laowo and adjacent areas. Unfortunately, in the absence of an effective conservation strategy, the population was extirpated by hunters. The remaining forest in the Zhiben Mountains is highly fragmented, and most of the suitable habitat for gibbons has been lost. Therefore, we expect that this newly found gibbon population is under extreme anthropogenic pressure. It is imperative that further investigations of this gibbon population be conducted immediately, and that the local and national governments implement effective conservation plans, including educating the local communities to protect this critically endangered primate population.

Observation of intra‐group and extra‐group copulation and reproductive characters in free ranging groups of western black crested gibbon (Nomascus concolor jingdongensis)

Black crested gibbons (Nomascus concolor) are 1 of only 3 gibbon species that have been observed in long-term polygynous groups, but their mating behavior and reproductive characters have never been reported. Based on population monitoring over 7 years and direct observation for 26 months of the study groups in Wuliang Mountain, central Yunnan, we describe for the first time the copulation behavior and breeding pattern of free-ranging western black crested gibbons. The gestation period of black crested gibbons is estimated to be between 6 and 7 months. The average breeding interval is 3.5 years, with infant independence at approximately 2.5 years. We observed 2 intra-group copulations and 5 extra-group copulations. Copulations were initiated when a female gave a 'solicitation' gesture. When a male made any mating attempt, the female might refuse it. These results demonstrate direct female mate choice. Both male and female gibbons dispersed from their natal groups and sometimes replaced paired adults in other groups. We observed no evidence of infanticide during inter-group conflicts or after replacement of adults. Together with extra-group copulations, these phenomena indicate a flexible social organization and complex mating system. We also observed a male-biased sex ratio among offspring. More genetic work is necessary to describe the effects of inter-group copulation and the genetic diversity of this population.

Proximity association in polygynous western black crested gibbons ( Nomascus concolor jingdongensis ): network structure and seasonality

We investigated the structure and seasonality of the proximity network in a group of polygynous western black crested gibbons (Nomascus concolor) using social network analysis. The spatial proximity changed seasonally and was affected by temperature and rainfall. Preferred proximity association was not distributed randomly among individuals. Kinship was one explanation for the social structure, as offspring preferred to maintain close proximity with their mothers. The proximity of infants to mothers decreased with age, and independent offspring had lower proximity to mothers than dependent ones. We found that the adult male had different proximity relationships with two different adult females. The frequency of proximity between the male and the infant-carrying female was significantly higher than that between the male and the female who had immigrated carrying one offspring of uncertain paternity into the group. Infanticide avoidance and/or predation protection for dependent infants might explain the proximity relationship differences. Temperature influenced group proximity association, with individual proximity increasing in the cold months and decreasing in the hot months. Group proximity decreased in months with higher anthropogenic disturbance.

Sonogram structure and timing of duets of western black crested gibbon in Wuliang Mountain

We studied the sonogram and timing of duets of three groups of Central Yunnan western black crested gibbons (Nomascus concolor jingdongensis) in Dazhaizi, Mt. Wuliang. The study was based on a 13-month field observation period, from March 2003 to March 2004. A Sony TC-D5 Pro2 recorder, Sony C-76 directed microphone, and Sony tape were used to record the duet bouts in March 2007 and March 2008. Signal/RTS 4.0 was used to analyze the sonogram of the duet. We first presented sonograms of all kinds of sound units in the duets made by western black crested gibbons. The adult male could produce boom, aa notes and modulated figures. Adult females produced great call or abortive great call. The two adult females in each group usually produced great calls synchronously. After the great call, males always immediately produced a modulated figure to coordinate with the female. The interval between the modulated figure and great call was 2.7 s. On average, groups sang on 53% of days monitored, and sang 1.09 duet bouts per singing day. 91.5% of the duets were produced between half an hour before and three hours after the sunrise. The average duration of the duets was 12.9 min, and females produced 4.6 great calls during one duet bout. The intervals between two successive great calls were generally 115 s. There was no significant difference in the duration and frequency of the duet bouts, but there was significant difference in the number of the great calls and intervals between great calls among groups.

Singing behavior and singing functions of black‐crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, central Yunnan, China

We used data on loud duetted and solo songs collected from one habituated polygynous group of black-crested gibbons (Nomascus concolor jingdongensis) on Mt. Wuliang, Yunnan, to test several hypotheses about the functions of these songs. The major functions proposed for loud gibbon songs include resource defense, mate defense, pairbonding, group cohesion and mate attraction. Duet bouts are generally initiated by adult males, who select the highest trees near to ridges or on steep slopes as singing trees. Such trees facilitate voice transmission and inter-group communication. Singing trees tended to be located near important food patches and sleeping sites, which supports the resource defense hypothesis. The adult male and two adult females always sang interactively, alternating male phrases with the females' stereotyped great calls, to produce the duets, and females rarely produced great calls if they were more than 30 m from the male. The two females usually produced great calls synchronously during the duet, especially when they were close together. These features support both the mate defense and pairbonding hypotheses. The number of great calls and their degree of synchrony transmit information about spatial relationships and possibly pairbond strength to members to neighboring groups and floating animals. During or after the duet bouts, the adult females and juvenile moved toward to the adult male; and group members maintained a close spatial relationship, which supports the group cohesion hypothesis. Other incidents observed suggest a mate competition role for duets. The adult male always sang when the females started duetting with the subadult male. The subadult male sang solo bouts, but they were not more frequent or longer than bouts initiated by the adult male. Although mate attraction is the likely function of subadult solos, it was not convincingly demonstrated. In conclusion, all hypotheses concerning the function of singing are supported by at least some of the data, and none can be excluded.

Gibbons under seasonal stress: the diet of the black crested gibbon (Nomascus concolor) on Mt. Wuliang, Central Yunnan, China

The diet of a habituated group of black crested gibbon (Nomascus concolor jingdongensis) was studied from March 2005 to April 2006 in the Wuliang Mountains, central Yunnan, China. Gibbons consumed 77 different plant species, one mammal-, two bird-, one lizard-, and two insect-species. Buds and leaves constituted 46.5% of the diet (21.0% vine leaves and buds, 19.2% tree leaves and buds, and 6.3% epiphyte leaves). Fruits, figs and flowers accounted for 25.5, 18.6 and 9.1% of the diet, respectively. There was marked seasonal variation in dietary proportions. Fruit varied from 0.3 to 82.7%; figs from 0 to 68.2%; tree leaves and buds from 1.5 to 83.3%; vine leaves and buds from 3.1 to 61.9%; and epiphyte leaves from 0 to 22.2% of the diet. Different food types dominated the diet in different months during the study period. The foli-frugivorous diet and extreme seasonal variation in the diet may be related to the harsh habitat of the study group.

Predation on giant flying squirrels (Petaurista philippensis) by black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China

Predation on vertebrates is infrequent in gibbons. In a 14-month field study of the central Yunnan black crested gibbon (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China, we observed gibbons attacking, killing and eating giant flying squirrels (Petaurista philippensis). During 845 h of observation on one study group, the gibbons attacked giant flying squirrels 11 times, and succeeded in 4 cases. Although all members of the group attempted to attack the squirrels, all four successful attacks were made by the same adult female. The victims were infants in three cases and a juvenile or sub-adult in one case. Black crested gibbons also attacked adult giant flying squirrels by grabbing their long tails and throwing them from the canopy, but they failed to catch or kill the prey in three cases observed. Passive meat sharing occurred in three out of four successful cases. Besides hunting giant flying squirrels, the black crested gibbons also ate eggs or chicks in two birds' nests and one lizard.

Seasonal Variations in the Activity Budget of Nomascus concolor jingdongensis at Mt. Wuliang, Central Yunnan, China: Effects of Diet and Temperature

We studied seasonal variation in the activity budget of a habituated group of Nomascus concolor jingdongensis at Mt. Wuliang, Central Yunnan, China from March 2005 to April 2006 via scan sampling at 5-min intervals. The study site is near the northern extreme of the distribution of hylobatids, at high altitude with extreme seasonality of temperature and rainfall. During the day, feeding manifested a bimodal pattern of high activity levels in mid-morning and mid-afternoon, whereas resting reached a peak at midday, with proportionally less time used for traveling. Annually, the group spent an average of 40.0% of the time resting, 35.1% feeding, 19.9% traveling, 2.6% singing, 1.2% playing, and 1.3% in other activities. The proportion of time allocated to activities showed significant monthly variations and was influenced by the diet and temperature. Gibbons increased traveling and playing time and decreased feeding time when they ate more fruit, and they decreased traveling, singing, and playing time and increased feeding time when they ate more leaves. Moreover, when the temperature was low, the gibbons decreased time traveling and increased time resting. In summary, black-crested gibbons employed high-effort activities when they ate more fruit and energy-conservation patterns when they ate more leaves and in low temperature. Behavioral data from the site are particularly useful in understanding gibbon behavioral adaptations to different sets of ecological conditions.

Effects of food and topography on ranging behavior of black crested gibbon (Nomascus concolor jingdongensis) in Wuliang Mountain, Yunnan, China

We studied the ranging behavior of a habituated group of black crested gibbons (Nomascus concolor jingdongensis) in a high, seasonal habitat on Mt. Wuliang, central Yunnan, China, between March 2005 and April 2006. Our results indicated that the total home range size for the study group was 129 ha, or 151 ha if the lacunae within the borders in which gibbons were not observed were included. This is a much bigger range size than that of other gibbon species. However, 69.7% of their activities occurred within 29 ha. The intensity of quadrant use was significantly correlated with the distribution of important food patches. The mean yearly daily path length was 1,391 m. Gibbons traveled farther when they spent more time feeding on fruit. To avoid often passing through ridges with little food, gibbons usually stayed in the same valley for successive days, and then moved on to another valley for another several days, which resulted in a concentrated ranging pattern.

Sleeping sites, sleeping trees, and sleep‐related behaviors of black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Central Yunnan, China

Data on sleep-related behaviors were collected for a group of central Yunnan black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China from March 2005 to April 2006. Members of the group usually formed four sleeping units (adult male and juvenile, adult female with one semi-dependent black infant, adult female with one dependent yellow infant, and subadult male) spread over different sleeping trees. Individuals or units preferred specific areas to sleep; all sleeping sites were situated in primary forest, mostly (77%) between 2,200 and 2,400 m in elevation. They tended to sleep in the tallest and thickest trees with large crowns on steep slopes and near important food patches. Factors influencing sleeping site selection were (1) tree characteristics, (2) accessibility, and (3) easy escape. Few sleeping trees were used repeatedly by the same or other members of the group. The gibbons entered the sleeping trees on average 128 min before sunset and left the sleeping trees on average 33 min after sunrise. The lag between the first and last individual entering the trees was on average 17.8 min. We suggest that sleep-related behaviors are primarily adaptations to minimize the risk of being detected by predators. Sleeping trees may be chosen to make approach and attack difficult for the predator, and to provide an easy escape route in the dark. In response to cold temperatures in a higher habitat, gibbons usually sit and huddle together during the night, and in the cold season they tend to sleep on ferns and/or orchids.

Can a Group Elicit Duets from Its Neighbours? A Field Study on the Black-Crested Gibbon (Nomascus concolor jingdongensis) in Central Yunnan, China

We tested the intergroup spacing hypothesis with a 13-month field study of the interaction of singing behaviour between 3 neighbouring groups of black-crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Central Yunnan, China. Neighbouring groups tended not to sing on the same day. While it did happen occasionally, a group seldom started a duet while its neighbour was singing, or within 5 min of the singing ceasing. The intersong intervals of 2 groups calling on the same day were similar or significantly longer than the intervals between any song bouts randomly selected from the same 2 groups when calling on different days. Groups did not sing in intergroup encounters and showed similar responses to neighbouring groups and groups with no common border. These results did not support the intergroup spacing hypothesis. The possible reasons are discussed.

Status and distribution pattern of black crested gibbon (Nomascus concolor jingdongensis) in Wuliang Mountains, Yunnan, China: implication for conservation

The western black crested gibbon (Nomascus concolor), or black gibbon, one of the lesser apes (Hylobatidae), is mainly distributed in Yunnan, China. Of the four recognized subspecies, N. c. jingdongensis is endemic to the Wuliang Mountain, central Yunnan, China. Of all the subspecies, this one has the largest population of any black gibbon. However, the data were all based on brief estimates. We carried out an extensive field survey on population and group distribution of the black gibbon in the Wuliang Mountains by use of loud morning songs and interviews with local people. Ninety-eight groups were confirmed and located in the mid-montane range of Wuliang Mountains. More groups are found on the east slope and the southern region than in the west and the north. Gibbons are more disjunctly distributed on the west slope, especially in the northern part. Deforestation in the late 1950s, 1960s and 1970s was the main reason for rapid loss of habitat and population decline. Hunting was another key reason for population decline and, in many cases, the main reason for local extinction.