India - Arunachal
Status and Biogeography of Primates of
Arunachal Pradesh, India

CC has sponsored studies by Dr. Jihosuo Biswas of an enigmatic macaque and subspecies of other primates in the state of Arunachal Pradesh. It was important since researchers in the northeast states of India had been puzzling over this mysterious macaque since the late 1990s. Some thought the mysterious primate was a small population of Thibetan or Pere David’s macaque (Macaca thibetiana) that occurs in China. Others thought it was some odd hybrid macaque or even a new species. Recently it was named the Arunachal macaque (Macaca munzala) but we felt that it needed closer study and Dr. Biswas had the interest to pursue it.

Arunachal Pradesh is a state of high ecosystem, altitudinal and biological diversity that includes nine species of primates. Biswas’ study focused on two districts in the extreme west (Tawang and West Kamang) and two districts in the extreme east of Arunachal Pradesh (Lohit and Changlang) which were sites of this unusual macaque. Thus this study was to shed more light on this “species” as well as to address some of the other subspecies differences of the capped langur and the hoolock gibbon of Arunachal Pradesh.

The survey was conducted in 33 sites in the four districts and located over 2500 individuals of six species. Local questioning of villagers further documented the presence of the slow loris, a nocturnal species. Three species (rhesus and Assamese macaques and capped langurs) were found in the western districts while seven species (rhesus, Assamese, pigtail and stumptail macaques, capped langur, hoolock gibbon and slow loris) were found in the eastern districts. For the first time, this study documented the eastern subspecies of the hoolock gibbon in India and the blonde bellied subspecies of the capped langur.

Enigmatic Macaque– A number of sightings of an enigmatic macaque have been made since 1997. They noted a darker more robust animal with a short tail, prominent cheek whiskers, white eyelids that emits a peculiar alarm call. These features seemed to be a mixture of features of Pere David’s macaque (M. tibetiana and the Assamese macaque subspecies. Recently, this animal was described as a new species (Macaca munzala). However, this study seems to indicate that this population is a geographic variation that occurs at the junction of the two subspecies of the Assamese macaque.

Variations in a population of the "enigmatic" macaque

Both populations of the enigmatic macaque from Arunachal Pradesh show shorter tail length, larger bodies with a great deal of color variation. They show a paler forehead and long whitish buff whisker hair more prominently in males. They also show longer pelage on the upper body. The tail is darker with white at the tip. Some of these characteristics like the more robust body, darker color and longer body hair could potentially be due to the higher elevations in the eastern districts. However, what is very significant is the tail to head/body length. When this length is compared with data on two subspecies of the Assamese macaque by Fooden a macaque expert, they match indicating a subspecific change near the western districts of Arunachal Pradesh. This study seems to indicate that these enigmatic macaques are from the eastern subspecies of the Assamese macaque (M.a. assemensis) but also recommends additional studies of the situation.

Hoolock Gibbon – There are two subspecies of hoolock gibbons with the western subspecies thought to be the only one found in India. However, this study was the first to document the eastern subspecies (see photo at right), extending its range into India. There was an important finding that there was greater forest fragmentation at lower altitudes where there is greater human habitation. Increased fragmentation was correlated with larger group sizes indicting the probability that subadults may have been prevented from leaving their natal groups to seek mates.

Capped Langur – In censusing capped langurs in Arunachal Pradesh, this study encountered, in the low altitudes of Lohit and Changland Districts, individuals that were intermediate in pelage color to Trachypithecus pileatus tenebrous, a western subspecies and the eastern blonde bellied subspecies, T.P.pileatus. The study found the blonde-bellied subspecies in India for the first time, but was unable to find the buff-bellied subspecies. See tenebrous capped langur at left.

The study of primates in Arunachal Pradesh and related projects in Assam, and Mizoram, Northeast India, have been funded in large part by multiple grants from the Margot Marsh Biodiversity Foundation and Primate Conservation, Inc. as well as individual donors to Community Conservation.