Semnopithecus entellus
Hanuman langur

The geographic range of Semnopithecus entellus (Hanuman langur) spans from Kashmir in north India and the Himalayas in Nepal, Bhutan, and Tibet south to Sri Lanka, east to Bangladesh and west to the Indus valley in Pakistan (Gron, 2008). It is thought that a single breeding pair resulted in the population found in southeast Bangladesh. (Gron, 2008; Mitra and Molur, 2008)

Hanuman langurs are found in a wide variety of habitats, ranging from arid to tropical evergreen rainforests. They are also known to live in close proximity to humans, including the city of Jodhpur, India, which has over a million inhabitants (Gron, 2008). They are forest dwelling primates in India but are found only in forest openings in Bangladesh (Farid Ahsan and Reza Khan, 2006). The amount of rainfall varies greatly throughout their range (10 to 200 cm). Hanuman langurs are able to withstand a wide range of temperatures, from -7˚C to 46˚C, and spend about 80% of their time on the ground. (Carlson, 2004; Farid Ahsan and Reza Khan, 2006; Gron, 2008)

Hanuman langurs have brownish gray fur, with a tinge of red on their dorsal surface and white fur on their ventral surface. Their feet, hands, face, and ears are black, and their face is framed with white fur. Their tail is usually longer than the body, with a white tip. Infants are born with fine, dark brown or black fur. Their skin is pale, but darkens to black by three months old. They are sexually dimorphic, with males being slightly larger than females. Males weigh about 13 kg and females weigh about 9.9 kg. Excluding their tail, males are about 64 cm long, and females are about 58.5 cm long. Male Hanuman langur tails average 91.0 cm and those of females average 86 cm. They have 32 teeth and their dental formula is 2/2 1/1 2/2 3/3. ("Old World monkeys I", 2004; Gron, 2008)

Hanuman langurs live in both polygynous and polygynandrous groups, and unpaired males form bachelor groups. Male dominance is usually determined through fighting, whereas younger, sexually mature females are higher ranking, and decrease in rank with age. Females advertise estrous via head shaking and presenting the anogenital region to potential mates. Females continue mating during gestation to prevent infanticide by dominant males. ("Old World monkeys I", 2004; Gron, 2008)

Females typically reach sexual maturity by 2.9 years of age, with males reaching sexual maturity by 5 years of age. Hanuman langurs breed between July and October, and parturition occurs between February and April. Gestation lasts for 200 to 212 days, after which a single infant is usually born. Although rare, females may also give birth to twins. ("Old World monkeys I", 2004; Gron, 2008)

Infant Hanuman langurs spend the first week of life with their mothers. After that, infants are also cared for by other females that have recently given birth to young; however, the mother still provides most of the care. By six weeks old, infants begin eating on their own. Weaning doesn’t begin until 8 months old and is complete by 13 months old. Between the ages of 9 to 12 months, infants are only around their mother 20% of the time. Males are forced to disperse before they become sexually mature, while females stay with their natal group. Hanuman langurs are independent by 2 years old. ("Entellus [=Sacred] Langur", 1998; Carlson, 2004; Gron, 2008)

Mothers are very protective of their infants, which often remain at the center of the group for increased protection. Females from surrounding groups sometimes kidnap infants, however, mothers often risk their lives to retrieve their offspring. ("Entellus [=Sacred] Langur", 1998; Carlson, 2004; Gron, 2008)

In captivity Hanuman langurs often live into their early thirties. In the wild, males can live to 18 years old, and females can live to 30 years old. (Gron, 2008)

Hanuman langurs are diurnal and semi-arboreal, spending 80% of their time on the ground using quadrupedal locomotion. They use trees primarily for sleeping. Dominance hierarchies play an important role in tree use behavior. The highest ranking male sleeps at the highest position in the tree, because it is the safest. Directly below the dominant male are females and their offspring, then younger females, with adolescent males at the lowest position. Hanuman langurs are gregarious and form groups ranging from 2 to over 100 members. They can be both polygynous and polygynandrous and sometimes form bachelor groups. During summer they are more active in the morning and evening, whereas in the winter they are more active during midday. (Carlson, 2004; Gron, 2008)

Hanuman langurs can have home ranges from 0.07 to 22 km^2. Bachelor groups typically have larger home ranges than other groups. They usually do not move their home ranges. (Gron, 2008)

Hanuman langurs have about 19 different types of calls. In the morning, mature males make a loud whooping call when leaving their sleeping trees. They may also make cacophonous barks if they are surprised by a predator. Adult and sub-adult males often grunt or cough during group movements. Isolation peeps can be heard from members who get lost or separated from their group. They often groom each other, which is performed according to local dominance hierarchies. Dominant Hanuman langurs groom one another and receive grooming more often than subordinate langurs. They use their vision to find food and move around their environment and females display estrous via head shaking. (Gron, 2008)

Hanuman langurs are primarily herbivores. Their diet is composed of leaves (52-61%), fruits (15-25%), flowers (4-13%), insects (0.4-3%), and other foods such as bark, gum, and soil (9-16%) (Gron, 2008). More developed leaves are preferred over young leaves. They are not highly selective foragers, and consume human food when available. In times of food shortage, they are known to consume bark. (Gron, 2008)

Hanuman langurs are preyed upon by leopards (Panthera pardus), dholes (Cuon alpinus), tigers (Panthera tigris), wolves (Canis lupus), and golden jackals (Canis aureus). They sleep in the upper forest canopy to avoid predators while resting; however, deforestation has reduced the number of roosting trees, giving predators easier access to langurs, potentially increasing predator induced mortality (Gron, 2008). (Gron, 2008)

Hanuman langurs live sympatrically with Bonnet macaques (Macaca radiata), toque macaque (Macaca sinica), and hooded leaf monkeys (Trachypithecus johnii). Each species occupies a distinct niche, therefore, they are able to live with one another with little to no resource competition. Soapberry bug nymphs (Leptocoris augur) rely on Hanuman langurs to remove fruit casings, enabling them to eat. (Gron, 2008)

Hanuman langurs are sacred animals in many parts of India. Various body parts are sometimes kept as amulets, which are thought to have a positive effect on the bearer (Gron, 2008). (Gron, 2008)

Hanuman langurs are known to raid crops and steal food from people’s homes. (Gron, 2008)

Hanuman langurs are listed as a species of "least concern" on the IUCN Red List of Threatened Species. It was previously listed as near threatened in 2004. (Mitra and Molur, 2008)

S. entellus was previously known as Presbytis entellus. They received their common name, Hanuman langur, from Hanuman who is the monkey-god. ("Old World monkeys I", 2004; Gron, 2008)