Golden snub-nosed monkey

The golden snub-nosed monkey (''Rhinopithecus roxellana'') is an Old World monkey in the subfamily Colobinae. It is endemic to a small area in temperate, mountainous forests of central and Southwest China. They inhabit these mountainous forests of Southwestern China at elevations of above sea level. The Chinese name is Sichuan golden hair monkey (四川金丝猴). It is also widely referred to as the Sichuan snub-nosed monkey. Of the three species of snub-nosed monkeys in China, the golden snub-nosed monkey is the most widely distributed throughout China.

Snow occurs frequently within its range, and it can withstand colder average temperatures better than any other non-human primate. Its diet varies markedly with the seasons, but it is primarily a herbivore with lichen.

Taxonomy

Biologists presently identify three subspecies of this monkey, which can be distinguished primarily by the length of their tails, as well as by certain skeletal and dental features. The dense human settlement of much of eastern Sichuan and the Han River valley of southern Shaanxi creates geographical separation between the three subspecies.

* Moupin golden snub-nosed monkey, ''Rhinopithecus roxellana roxellana''. This subspecies is found in the mountainous areas flanking the Sichuan Basin from the west and north. According to the estimates made between 1995 and 2006, the population includes some 10,000 individuals, living mostly in Sichuan. Of them, some 6,000 lived in the Min Mountains of northern Sichuan, 3,500 in the Qionglai Mountains further west, and 500 in the Daxiangling and Xiaoxiangling ranges of south-central Sichuan. Smaller groups are also found just north of Sichuan border, in the border counties of Gansu ( Wen County; about 800 individuals in eight troops) and Shaanxi ( Ningqiang County, about 170-200 individuals in one or two troops).
* Qinling golden snub-nosed monkey, ''Rhinopithecus roxellana qinlingensis''. According to an estimate published in 2001, this subspecies included some 3,800-4,000 individuals (about half of them adults) in 39 in Qinling Mountains of southern Shaanxi. The Qinling Mountains are separated from the more southern Min– Daba Mountains belt by the wide and comparatively densely populated Han River valley.
* Hubei golden snub-nosed monkey, ''Rhinopithecus roxellana hubeiensis''. Members of this subspecies reside in the Daba Mountains (in particular, their Shennongjia section) of the westernmost Hubei ( Shennongjia Forest District, Fang, Xingshan and Badong counties) and the northeastern Chongqing Municipality. According to a 1998 estimate, the population included 600–1,000 individuals in five to six troops. In 2005, the management of the Shennongjia Nature Reserve reported that the population had grown between 1990 and 2005 from 500 to over 1200.Number of golden monkeys doubled
(Xinhua, www.chinaview.cn, 2005-08-08)

Physical characteristics

The adult and subadult golden snub-nosed monkey is sexually dimorphic.

Adult males (estimated at over 7 years of age) have large bodies covered with very long, golden guard hairs on their backs and cape area. The crest is medium brown while the back, crown to nape, arms and outer thighs are deep brown. The brown crest also contains physically upright hairs, whose shape is useful for individual identification. Also, when their mouths are open, researchers can observe long canines. They are usually between 58 cm and 68 cm and weigh about 16.4 kg.

Subadult males (estimated at 5–7 years of age) have a similar sized body as the fully developed male adult, but have a more slender body. The golden guard hairs on the cape are short and sparse, and their median brown crests show microbanding, while also turning from a brown color.

Adult females (estimated at over 5 years of age) are smaller in size and are about half the size of adult males. The dorsum, crown to nape, cape, arms and outer thighs are brown to deep brown in some of the older females. However, golden guard hairs are also present on the back and cape area, but they are shorter in length than in the males. The brown crest shows microbanding. Their breasts and nipples are large and easily visible which is also useful for identification. After pregnancy, it is common to observe infants and newborns hanging beneath the abdomen of females when they are climbing or walking. They are usually between 47 cm and 52 cm and weigh about 9.4 kg.

Subadult females (estimated at 3–4 years old) are smaller than adult females and are about two-thirds the size. The body hair is brown, gradually turning golden but lacking the golden guard hairs. Their median brown crest also shows microbanding. Their breasts and nipples are also not as large as they are in adult females.

Juveniles (ranging from at least 1 year of age to 3 years old) are quite small, being less than two-thirds the size of adult females. Their body hair is light brown, gradually turning reddish gold. The rest of their body (dorsum, crown to nape, cape, arms and outer thighs) hair is brown. Golden hairs in the dorsum or cape area are not recognizable nor is the median brown crest present in subadult to adult females and males. Sexual discrimination is difficult because their external genital organs are underdeveloped.

Infants (estimated at 3 months to 1 year old) are light brownish gray or light brown, appearing white in sunlight. They are often observed playing with juveniles or other infants, but are noted to spend most of their time beside their mothers or sucking milk. They are also observed clinging from the front of their mothers (primarily the lower abdomen) for protection, feeding, and nurturing. Their sex of the individual cannot be distinguished at this point of time as well as in Newborns.

Newborn babies (estimated at less than 3 months of age) are dark to light gray. They turn light brownish grey after about 2 months. They are also observed rarely leaving their mothers or other females carrying them, known as alloparenting. Sex at this time is indistinguishable.

Habitat and distribution

The distribution of the golden snub-nosed monkey is limited to temperate forests on mountains in four provinces in China: Sichuan, Gansu, Shaanxi, and Hubei. This monkey is found at elevations of 1,500-3,400 m. Within this area, vegetation varies with altitude from deciduous, broadleaf forests at low elevations to mixed coniferous, broadleaf forests above 2,200 m and coniferous forests above 2,600 m. Average annual temperature is 6.4 °C with a minimum of -8.3 °C in January and a maximum of 21.7 °C in July.

Home range size varies seasonally. The change in home range size and location is dependent upon the availability and distribution of food. The total area covered by seasonal home ranges is surprisingly large for a species. One of the largest home ranges found covered 40 km².

Behavior

The golden snub-nosed monkey is found in groups ranging in size from 5-10 individuals to bands of about 600. The social organization of this species can be quite complex. The one-male-units (OMUs) are the basic social unit within groups of golden snub-nosed monkeys with many of the OMUs forming a bigger group. These multi-tier societies consist of several OMUs that include one adult male plus a number of adult females and their offspring. Some observers have even come to conclude that these large foraging groups are multi-male and multi-female societies.

The male may stay solitary, often remaining away from the rest of the group members as they rest. Adult females tend to socialize more with one another than with other males or juveniles. Group members remain close to one another, interactions between different OMUs often result in confrontations. Females of the golden snub-nosed monkey are usually observed to form several close associations with other females. However, in conflicts against other units in the surrounding site, both males and females support each other, while also protecting their young (usually observed at a distance by putting the young in the center of the pack). Unusually for a harem-forming species, infanticide by males is averted. Female snub-nose monkeys will deliberately have "affairs" with all resident males in the surrounding area behind the harem-master's back, which in turn creates paternity confusion and means newly established alpha males will not risk killing what could be their own offspring. In turn females will have more reproductive success and less infant losses.

Protecting the young is a group effort. Mothers often have helpers assisting them with the care of their young. When faced with danger from a predator such as the northern goshawk (''Accipiter gentilis''), the young are placed at the center of the group while the stronger adult males go to the scene of the alarm. The rest of the day, the members of the group remain closer to one another with the young protected at the center.

There is little information available on the sleeping cluster patterns of the Sichuan snub-nosed monkeys. However, in a detailed observation of the free-ranging band in the Qinling Mountains in central China, results have suggested that winter night activity of ''Rhinopithecus roxellana'' is a compromise between antipredator and thermoregulatory strategies and an adaptation to ecological conditions of their temperate habitat. Keeping warm is critical for survival in freezing temperatures, but their thick coats can provide this warmth as well as sleeping in these clusters. Monkeys often sleep in the lower stratum of the tree canopy, avoiding the upper canopy where it is cold and windy. They form larger sleeping clusters at night than in the daytime. The most common types of night-sleeping clusters were adult females and their young, followed by adult females with other adult females. Adult males are usually observed sleeping by themselves or on the lookout for predators or dangers.

There are several hypotheses to explain the formation of sleeping clusters, the most important one being a thermoregulatory process. The thermoregulatory hypothesis suggests that a primary function of sleeping in clusters is the conservation of heat during cold temperatures. Along with thermoregulation, safety from predators is an important principle underlying the formation of sleeping clusters in primates. This antipredation hypothesis suggest that increased cohesion and large sleeping congregations might facilitate predator detection and enhance group defense.

Reproduction

Females are sexually mature at about 5 years old. Males are sexually mature at about 5–7 years old. Mating may occur throughout the year but peaks in the month of October. This approximates gestation at 6–7 months in length. The golden snub-nosed monkey gives birth from March to June.

In primate research, although male-male competition for mates and female mate choice are the common causes of sexual selection, female-female competition over males is especially important in polygynous species. The Sichuan snub-nosed monkey is a seasonal breeding species of colobine endemic to China, and lives in a multi-level social system. Because the basic social and reproductive unit is the harem or one male unit (OMU), which consists of a single resident male, a number of adult females, sub-adult females, juveniles and infants, it has been suggested that sexual competition in this polygynous species is skewed. Females faced with multiple competitors will exhibit a high level of sexual competition, while the single resident male will not experience within-group sexual competition. They also have up to 3 babies.

Diet

The golden snub-nosed monkey eats (from greatest to least amount) lichen