Semnopithecus hector (Pocock, 1928)

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cercopithecidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 550-755 : 734

134.

Terai Sacred Langur

Semnopithecus hector

French: Langur du Terai / German: Tarai-Hulman / Spanish: Langur de Terai

Other common names: Gray Langur, Hanuman Langur, Kumaon Langur, Lesser Hill Langur, Tarai Gray Langur, Tarai Sacred Langur

Taxonomy. Pithecus entellus hector Pocock, 1928 ,

India, Sitabani, Ramnagar, Kumaon, 600 m above sea level.

S. hector was listed by W. C. O. Hill in his 1939 review of Asian langurs as a subspecies of S. schistaceus . C. P. Groves in his 2001 Primate Taxonomy considered hector sufficiently distinct as to warrant the status of species. Genetic analyses may yet indicate a revision of this arrangement. M. L. Roonwal separated gray langurs of South Asia into a northern group and a southern group based on tail carriage. S. hector is of the northern group (Type IB), with the tail looping forward but held up above the back with the tip out-curved. Monotypic.

Distribution. Himalayan foothills in N India (states of Uttarakhand, Uttar Pradesh, and W Bengal), and W & C Nepal; it also probably occurs in SW Bhutan near Pankhabari.

Descriptive notes. Head—body 58.4-76.2 cm, tail 75-99.1 cm; weight 17 kg (males) and 17-7 kg (females); these measurements were taken from a sample in which the Terai Sacred Langur and the Nepal Sacred Langur (S. schistaceus ) were considered synonymous. Coat of the Terai Sacred Langur is long and thick, with a plush grayish-yellow to pale orange over body and a dark line running down back. Underside is bufty-white. Fur acquires a brownish tinge below elbows and knees. Hands and feet are pale. Head is a striking white, and cheek whiskers are long and whitish, forming a bushy halo around the jet-black face. Crown is parted neatly along the midline. Tail tip is white.

Habitat. Semi-evergreen sal ( Shorea robusta, Dipterocarpaceae ) forest, moist deciduous forests of the Siwalik Hills, and alpine cedar and mid-elevation oak forest in the Himalayan foothills, and the Terai (a belt of marshy grasslands savannas and forests south of outer foothills of the Himalaya and Siwalik Hills, and north of the Indo-Gangetic Plain, at elevations of 150-1600 m). Winter weather is harsh, with snowstorms and temperatures below freezing in December—February.

Food and Feeding. Terai Sacred Langurs eat flowers and flower buds, unripe and ripe fruit, seeds, buds, young and mature leaves, petioles, pith, bark, wood, gum, insects (including their excreta), and soil. In year-long studies by A. Koenig and C. Borries and colleagues at Ramnagar, 64% of feeding time was spent on leaves, 15% fruits, 6% flowers, 5% other plant parts, and 10% on insects and soil. Sixty-nine plant species contributed 90% of the diet, and of these, 57 contributed less than 1% to the diet, a further nine contributed 19-2%, and just three species contributed 54%. Particularly important were Spatholobus parviflorus (Fabacae), a leguminous vine that provided flowers, fruits and leaves, Terminalia bellirica ( Combretaceae ), and Dillenia pentagyna (Dillenicaeae). Terai Sacred Langurs also feed on crops and in orchards.

Breeding. The Terai Sacred Langur is a seasonal breeder; births occur only in January—June, with nearly 50% of all births occurring in March. Mating is frequent in May-June, but conceptions are restricted to July-November, with ¢.50% occurring in August. The gestation period is ¢.209 days. The menstrual cycle averages 26-4 days. Females give no visible sign of menstruation. Females are proceptive; they present their anogenital region to males, shaking their head and lowering their tail. The mean age atfirst birth is 6-7 years (range 6-8). Lactation lasts ¢.25 months, but it can be as long 31 months. Sixty-five percent of females weaned their infants only when they were pregnant again. Studies at Ramnagar have shown that males can, infrequently, be infanticidal after immigrating into a new group. When an infant is raised successfully to independence, the average interbirth interval is 2-4 years. The intervalis halved (1-2 years) if the infant dies before it is one year old, and reduced to two years if it dies in its second year. In five groups at Ramnagar, male infanticide accounted for 30-8-62-5% of infant mortalities during the first two years of life. Females copulate even when they are pregnant, supposedly so as to confuse paternity and protect their offspring from infanticide. Nevertheless, most attackers (91%) were resident males and killed infants despite having copulated with the mother if they had not been a member of the group when the infant was conceived or born.

Activity patterns. Terai Sacred Langurs are diurnal, arboreal, and terrestrial. At Ramnagar, they spend ¢.20% of their day on the ground and the remainder in trees.

Movements, Home range and Social organization. Groups of Terai Sacred Langurs are unimale—multifemale or (mostly) multimale-multifemale. Group sizes average 18-3 individuals (range 7-41), with an average of 2-5 adult males and 6-6 adult females. About 72% of bisexual groups have more than one adult male (as many as nine). Females are philopatric, they remain in their natal groups. Males disperse at c.6 years old when they are still considered subadults. Females form a linear and stable dominance hierarchy, with younger adult females being the most dominant; older females gradually drop down in the hierarchy. Males do not form permanent all-male bands as is found in other gray langurs. They remain solitary, form pairs , or form ephemeral all-male groups of up to five individuals. Male replacement involves staggered immigrations and exclusions, and it is gradual. A dominant male’s tenure can last six or more years. Male Terai Sacred Langurs that are fathers or were resident when infants are born are highly protective of them. When entering a new group, they do it on their own and establish their dominance within a few days. The resident male either stays in the group as a subordinate or is expelled. The density of Terai Sacred Langurs at Ramnagar has been estimated at 26 ind/km?. In the Khumaon Hills, Himalaya, the density is 97 ind/km?.

Status and Conservation. CITES Appendix I. Classified as Near Threatened on The IUCN Red List. The Terai Sacred Langur is listed under the Nepal National Park and Wildlife Conservation Act (1973) as a common animal. It occurs in three protected areas: Corbet Tiger Reserve, Rajaji National Park, and Valmiki National Park in India and several protected areas in Nepal. The population is threatened by development activities such as mining and firewood collection, charcoal collection and production, habitat loss due to human settlements, and electrocution from powerlines.

Bibliography. Bennett & Davies (1994), Borries (1997), Borries et al. (1999, 2001, 2011a), Brandon-Jones (2004), Groves (2001), Karanth (2010), Kirkpatrick (2011), Koenig et al. (1997, 1998), Molur et al. (2003), Oppenheimer (1977), Pocock (1928), Roonwal (1984, 1986), Roonwal, Prita & Saha (1984).

Figures

132. Bengal Sacred Langur (Semnopithecus entellus), 133. Chamba Sacred Langur (Semnopithecus ajax), 134. Terai Sacred Langur (Semnopithecus hector), 135. Nepal Sacred Langur (Semnopithecus schistaceus), 136. Malabar Sacred Langur (Semnopithecus hypoleucos), 137. Tufted Gray Langur (Semnopithecus priam), 139. Nilgiri Langur (Semnopithecus john)

Distribution. Himalayan foothills in N India (states of Uttarakhand, Uttar Pradesh, and W Bengal), and W & C Nepal; it also probably occurs in SW Bhutan near Pankhabari.