The Assam macaque has a yellowish-grey to dark brown pelage. The facial skin is dark brownish to purplish. The head has a dark fringe of hair on the cheeks directed backwards to the ears. The hair on the crown is parted in the middle. The shoulders, head and arms tend to be paler than the hindquarters, which are greyish. The tail is well-haired and short. Head-to-body-length measures, and the tail is long. Adult weight is.
The Macaca assamensis "Nepal population" is endemic to Nepal and likely in some way distinct from the two recognized subspecies, which occupy adjacent areas to the southeast and east of the range of M. assamensis. There is a gap in northeastern India between the two main population pockets, specifically between central Bhutan and the south side of the Brahmaputra River; the east bank of its upper course marks the division between the two recognized subspecies:
The western Assamese macaque, M. a. pelops, is found from central Nepal through Uttar Pradesh, Sikkim, Assam and northernmost West Bengal in northern India, into central Bhutan and the Sundarbans in Bangladesh.
During surveys carried out in 1976, 1978, and 1984 in Nepal, Assam macaques were found to be patchily distributed along rivers in tropical and subtropical forests at altitudes from. They are apparently absent from areas west of the Kaligandaki River. In India, they live in tropical and subtropical semievergreen forests, dry deciduous and montane forests, from the sea level to altitudes of. They usually inhabit hill areas above, but in the wetter east they may occur even in the lowlands, and frequent areas that only marginally reach this altitude. In Laos and Vietnam, they prefer high altitudes, usually above. In forests on limestonekarst, they occur in much lower elevations.
Ecology and behaviour
Assam macaques are diurnal, and at times both arboreal and terrestrial. They are omnivorous and feed on fruits, leaves, invertebrates and cereals. In Namdapha National Park, Arunachal Pradesh, 15 groups were recorded in 2002 comprising 209 individuals. The population had a group density of 1.11 individuals per, and an average group size of 13.93 individuals. During a survey in Nepal's Langtang National Park in 2007, a total of 213 Assamese macaques were encountered in 9 groups in the study area of. Troop sizes varied between 13 and 35 individuals, with a mean troop size of 23.66 individuals, and comprised 31% adult females, 16% adult males, and their young of various ages. They preferred maize kernals, followed by potato tubers, but also raided fields with wheat, buckwheat, and millet.
Threats
The threats to this species' habitat include selective logging and various forms of anthropogenic development and activities, alien invasives, hunting and trapping for sport, medicine, food, and the pet trade. Additionally, hybridization with adjacent species poses a threat to some populations.
Conservation
Macaca assamensis is listed in CITES Appendix II. It is legally protected in all countries of occurrence. For the populations in India, the species is listed under Schedule II, part I of the Indian Wildlife Act.
