Black Snub-nosed Langur (Pygathrix bieti)

MORPHOLOGY:
This species has a sacculated stomach to assist in the breakdown of cellulose. The black snub-nosed langur has mostly a black pelage color. Newborns have a completely white pelage, and in juveniles (age 1.5 to 4 years) the pelage turns to light yellow then to gray (Wu, 1993). Newborns also have a blue face and fingers and toes that are pink (Ji et al., 1998). In subadults (age 4 to 8) the fur on the back, sides of body, and ends of limbs turn first to light brown then eventually black (Wu, 1993). In the adult (over 8 years) the back, top of the head, ends of limbs, and the end of the tail are dark brown to black in color (Wu, 1993). The buttocks, outer sides of the thighs, upper of the ear, the sides and front of the neck, the sides of the chest, the armpits, and the abdomen from the last ribs to the groin are white in color in the adult (Wu, 1993). Adults have pink-colored facial skin around the muzzle (Rowe, 1996; Groves, 2001). The facial skin around the eyes of adults is pale yellowish or greenish (Groves, 2001). The black snub-nosed langur has a dental formula of 2:1:2:3 on both the lower and upper jaws (Ankel-Simons, 2000). In this species there is a high degree of sexual dimorphism in the canine dental complexes, upper canine breadths, and lower third premolars (Jablonski and Pan, 1995, 1991). There is also sexual dimorphism in the pelage with adult males having long capes, long forelimb fringes, and long crown hairs (Jablonski and Pan, 1991). The black snub-nosed langur has scapulae that shaped like those found in brachiators (Jablonski et al., 1992). The average body mass for an adult male is 17 kilograms and for an adult female it is 12 kilograms (Kirkpatrick, 1995).

RANGE:
The black snub-nosed langur is found in the country of China. This species occurs from the YunLing Mountains in northwestern Yunnan and southeastern Tibet, west of the Jinsha River and east of the Lancang River (Li et al., 1981; Long, 1992, 1994; Jiang et al., 1995; Long and Kirkpatrick, 1991). Where the black snub-nosed langurs lives, snow is common for part of the year. This species is found in the counties of Deqin, Weixi, Lijiang, Jianchuan, Lanping, and Mangkang in China (Li et al., 1982). This species is found in high-altitude, evergreen forests, with the canopy consisting primarily of fir, Abies spp., spruce, Picea spp., evergreen oak, Quercus spp., and Rhododendron spp. (Ren et al., 1996/1997; Happel and Cheek, 1986). Long et al. (1994) found that this species prefers the fir-larch forest between the Yangtze and Mekong rivers. At Bamei, northern Yunnan Province, China, the black snub-nosed langur was found to live primarily in cypress forests (Zhong et al., 1998). During the winter this species uses the forest belt at an altitude of between 3,400 to 4,100 meters (Zhao et al., 1988).

ECOLOGY:
The black snub-nosed langur is a folivorous species, although Kirkpatrick et al. (2001) report that lichens are the most important food consumed by this species. Long et al. (1998) found that at Wuyapuya, China, 91% of the feeding records were of a single lichen species, Bryoria nepalensis, which is most dense in fir trees. Lichens eaten include a fruticose lichen Bryoria and Usnea spp. (Kirkpatrick et al., 2001; Happel and Cheek, 1986). The diet may be supplemented in the winter with bark and in the summer with young leaves and small berry-like fruit (Long and Kirkpatrick, 1991). Yang and Zhao (2001) found that at Lijiang, China the primary food source of this species was bamboo leaves and not lichens, where bamboo leaves constituted 59% of the diet, dicotyledon leaves 28%, lichens 5%, and seeds 4%. Bamboo leaves are richer in proteins but poorer in non-structural carbohydrates compared with lichens (Yang and Zhao, 2001). Wu (1994a) found that the primary food source for this species is the leaves and stems of Monocotyledoneae. Rodents, e.g. Eothenomys proditor, may also be consumed by this species (Yang and Zhao, 2001). This species may also eat grasses found on the ground, tree bark, oak nuts (acorns), and pine nuts (Zhao et al., 1988; Wu and Xian, 1994; Zhong et al., 1998). Moss may be part of the diet of the black snub-nosed langur (Long et al., 1994). Leaves from conifer trees do not constitute a large portion of the diet of this species (Long et al., 1994). Acorns are eaten by peeling the nut, and eating the kernel while discarding the shell (Zhong et al., 1998). The black snub-nosed langur bands forage mainly in the early morning and late afternoon and during midday will sleep for about two hours (Yang, 1988; Long et al., 1998).

This is a semi-terrestrial and diurnal species (Wu and Xian, 1994). Kirkpatrick and Long (1994) suggest that terrestriality is common (10-35% of the day), but this species is primarily arboreal. Terrestrial behavior is found more above the tree line and arboreal behavior is found more in the forest (Kirkpatrick and Long, 1994). When there is heavy snow, groups tend to move to lower elevations, but then return within a few days (Kirkpatrick and Long, 1994). Band sizes for this species can be up to 200 individuals (Kirkpatrick et al., 1998). Groups of this species tend to rest, sleep, and feed in low-lying places (Wu, 1993). Groups have large ranges and may take almost a decade to cover the entirety of their range (Zhong et al., 1998). Seasonal patterns in home range use are affected by feeding ecology (Kirkpatrick and Long, 1994). In captivity this species was found to have two rest periods, one in the early morning and one in the afternoon (Jiang et al., 1995). This species spends 60% of the time foraging and feeding (Jiang et al., 1995). Long et al. (1998) found that black snub-nosed langurs will spend 39% of the time feeding, 35% resting, 10% moving, and 16% engaged in other activities (play, grooming, holding infants, and display). Males will spend most of their time feeding and females will spend most of their time resting (Long et al., 1998). Zhong et al. (1998) found that females spent the least amount of time resting amongst group members and juveniles spent the most amount of time feeding. Resting was found to mainly occur on rock outcroppings, which may be because predators can be spied more easily and the rocks heat up during the day providing warmth in the cold winter months for the black snub-nosed langur (Long et al., 1998). Groups will move between sleeping and feeding sites in a single file line (Wu, 1994b). This species will sleep in trees in valleys (Rowe, 1996).

Humans, Homo sapiens, are the major predator of the black snub-nosed langur and human encroachment is leading to a loss of habitat (Long and Kirkpatrick, 1991). Mass killings by humans of up to 30 individuals in a day have been noted (Long and Kirkpatrick, 1991).

LOCOMOTION:
The black snub-nosed langur moves through the forest and on the ground quadrupedally (Fleagle, 1988). This quadrupedalism is of a slow climbing type, and on the ground they walk in a digitigrade fashion (Wu, 1993). This species was found to spend 22% of the time on the ground (Long et al., 1998). On the ground, most of the time is spent on rock outcrops (92% of the time) (Long et al., 1998). The black snub-nosed langur will climb rocks and steep precipices (Wu and Xian, 1994; Wu, 1992). Semi-brachiation is found in juveniles but disappears during adulthood (Wu, 1993, 1994b; Jablonski et al., 1992). Juveniles have a larger locomotor repertoire than adults (Wu, 1994b). Leaping behavior increases during an individual's life and is used in with quadrupedal behavior to move amongst the trees (Wu, 1993; Wu and Xian, 1994).

SOCIAL BEHAVIOR:
This species is unique amongst the colobines in that it has a multi-tiered social system (Kirkpatrick et al., 1998). The first level is a unimale group composed of one male, 2-5 adult females, and juveniles of both sexes (Kirkpatrick et al., 1998). These groups come together to form bands that can reach up to 200 members composed of 15-18 unimale groups (Kirkpatrick et al., 1998; Kirkpatrick, 1996). There are also all-male groups composed of subadult and adult males (Kirkpatrick et al., 1998). Males in bands will become aggressive with each other if they are 2-5 meters from each other (Kirkpatrick et al., 1998). The bands stay together for much of the year and only tend to split up during the breeding season (Kirkpatrick et al., 1998). Bands coming together and the size of the band is thought to be influenced by the female members (Kirkpatrick et al., 1998). The bands form because of competition for food, mainly lichens in this case, where females can observe potential competitors for food (Kirkpatrick et al., 1998). Food quality is important for reproductive success for females, and forming large bands can help in avoiding food patches that are depleted (Kirkpatrick et al., 1998). It is thought that unimale groups form because of male competition for mates in a highly seasonal environment (Kirkpatrick et al., 1998).

Intraband aggression tends to be low (Kirkpatrick et al., 1998). Social grooming occurs more in the unimale group by females than males, and occurs only slightly in juveniles (Kirkpatrick et al., 1998). Alloparental care by juveniles has been found to occur in this species (Kirkpatrick et al., 1998). Males are dominant over females when feeding in captivity (Jiang et al., 1995). Females will wait until the male is done feeding or will take food away and fed at a distance from the male (Jiang et al., 1995). In captivity males would not allow females to feed in their vicinity and males tend to feed for loner periods of time than females (Jiang et al., 1995).

VOCAL COMMUNICATION:

infant separation call: This call sounds like "waw-waw" and is given by infants looking for adult conspecifics (Li et al., 1982).

food satisfaction call: This call sounds like "Ga-Ga", much like the crow, Corvus monedula (Li et al., 1982). This call is given by an individual when they find a rich food source at the top of a tree (Li et al., 1982).

OLFACTORY COMMUNICATION:

VISUAL COMMUNICATION:

TACTILE COMMUNICATION:
social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals. Adult females groom more than adult males, with the adult males only grooming about a fourth of the time of the adult female (Jiang et al., 1995).

REPRODUCTION:
The black snub-nosed langur gives birth to a single offspring. The menstrual cycle of this species is about 26.2 days (Ji et al., 1998). Sexual maturity occurs at 5-6 years for males and 4-5 years for females (Ji et al., 1998). In captivity mounting behavior occurred at higher frequencies from June to December (Ji et al., 1998). In the wild copulations were found to occur primarily in August and September and most births occurring from March to April (Kirkpatrick, 1996). Mounting behavior for this species usually occurs in the morning, at dusk, or after eating (Jiang et al., 1995). The adult female will sometimes solicit mounting from the adult male by raising the buttocks towards the adult male (Jiang et al., 1995). During mounting, the adult male will grasp the waist of the adult female with the hands and keep the feet on the substrate (Jiang et al., 1995). The duration of intromission is from 20 to 60 seconds (Ji et al., 1998).

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Last Updated: October 12, 2003.
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