BLACK-FOOTED GRAY LANGUR

Semnopithecus hypoleucos

Geographic Distribution and Habitat
Black-footed gray langurs, also called dark-legged Malabar langurs and Malabar sacred langurs, are endemic to the Western Ghats, a mountain range on the southwestern coast of the Indian peninsula. They are found at altitudes ranging between 300 and 3,900 feet (100–1,200 m) in the patchy rainforests and deciduous or scrub forests of southwestern Karnataka, northern Kerala, and southwestern Maharashtra states. Some of these are protected forests. In addition, they are fairly widely distributed in peninsular India surrounded and limited by the tufted gray langur (Semnopithecus priam) on the east and south-east, and Nilgiri Langur in the south.

TAXONOMY IN TRANSITION

The taxonomy of the Semnopithecus genus, the taxon of the gray langurs, is still unresolved. Until fairly recently, all gray langurs were traditionally thought to be one species, Semnopithecus entellus, with up to 16 subspecies. S. entellus is now recognized as a distinct species and is commonly called the northern plains gray langur or the Hanuman langur. The black-footed gray langur (Semnopithecus hypoleucos), the subject of this profile, was recognized as a distinct species in 2005, having previously been considered a subspecies of the southern plains gray langur (Semnopithecus dussumieri). However, the southern plains gray langur classification has, even more recently, been deemed invalid. There are now eight recognized gray langur species: the northern plains gray langur (S. entellus), the Kashmir gray langur (S. ajax), the Tarai gray langur (S. hector), the black-footed gray langur (S. hypoleucos), the tufted gray langur (S. priam)the Nepal gray langur (S. schistaceus)the purple-faced langur (S. vetulus), and the Nilgiri langur (S. johnii).

Black-footed gray langur geographic range Map: IUCN, 2020

Size, Weight, and Lifespan
Male black-footed gray langurs are about 29 inches (75 cm) tall and weigh between 35 and 40 pounds (16–18 kg). They are larger than females, which average 25 inches (65 cm) tall and weigh 19 pounds (9 kg). The tails in both genders are an impressive 35–39 inches (90–100 cm) long.

These monkeys can live up to 30 years.

Appearance
Black-footed gray langurs are slender with long limbs and delicate features. They have black triangular-shaped faces. Their eyes are wide and hazelnut in color. Their nose forms a straight line down the middle of their face and their nostrils are vertical. Their chin is very small and their lips form a horizontal line under their nose.

The black hair above the eyes points outward. In some individuals it appears as a brown band or streak above the eyes that extends to the sides and up to the ears. The face is surrounded by whiskers and the chin ends in a tuft of hair that looks like a little beard. The hair on top of the head, back, and limbs is a grayish-beige color, whereas the belly is brighter and almost orange in those monkeys who live in wetter and humid areas. The inside of the thighs is a light straw color. In fact, the scientific name of this monkey (hypoleucos) comes from two Greek words: “hupo,” which means “under,” and “leukos,” which means “white.”

Some individuals have black fingers, hands, and wrists; others also have black arms up to the elbow, sometimes up to the shoulder. All have black feet.

The tails of these monkeys are described as having a “southern” carriage, meaning that they keep their tails looped backwards away from the head. This tail carriage mode is seen in gray langurs found south of the Narmada and Krishna rivers in southern India.

What Does It Mean?

Inflorescence:
The complete flower head of a plant including stems, stalks, bracts, and flowers.

Matrilineal:
Familial relationships that can be traced through a female.

Morphotype:
Any of a group of different types of individuals of the same species in a population.

Sacculated:
Having a series of sack-like compartments.

Visit the Glossary for more definitions

Photo credit: Daniele Colombo-Flickr/Creative Commons

Diet
Langurs are leaf eaters, so most of their diet consists of mature foliage from deciduous and evergreen trees. Their sacculated stomach is adapted to this type of diet. They also eat buds, flowers and fruit, bark, gums, and a few insects. The forests in which they live are degraded but do offer a wide variety of trees that bear fruit throughout the year. They get most of their water from food.

There are, however, some local differences. At Bhimashankar Wildlife Sanctuary, for instance, the black-footed gray langurs seem to be especially fond of a wild banana plant locally known as rankeli or kavadar. They like to gorge on their leaves, inflorescence, and fruits.

Behavior and Lifestyle
These very social monkeys forage during the day, jumping from one tree to another to find the best leaves. They walk on all fours while on the ground and are able to hop and leap with their back legs while keeping their body upright.

At night, they climb into the trees to branches as high as 80 feet (25 m). This is a strategic choice on their part to avoid predators while sleeping. The higher the branches, the more time they have to escape by jumping from tree to tree. The height also allows them to cool off during the hot summer nights. The groups move to different strata and areas of the forest depending on precipitation levels and temperatures, but overall, the species tends to remain in the western and mid-western Ghats regions of southwest India. Their territory does not overlap with that of other gray langur species.

Daily Life and Group Dynamics 
Gray langurs live in troops which average 20 to 100 individuals. Some groups are uni-male and multi-female, others are multi-male and multi-female. There are also some all-male groups, but these tend to be temporary and only occur during the mating season or after a takeover. There are frequent power shifts and dominant males do not hold their position for longer than 18 months as a rule. The status of females is not static either; females of reproducing age outrank younger and older ones.

After leaving their native groups, but before joining other groups or starting their own, adolescent males live together.

Female social groups and ranks are matrilineal. They rest, travel, and forage together. They groom each other regardless of rank, but the highest ranking females always receive the most grooming.

Fun Facts

All gray langurs are generally incorrectly referred to as Hanuman langurs. However, only the northern plains gray langur (Semnopithecus entellus) bears that common name.

The “rankeli” or kavadar” (E. superbum) is a wild banana plant that grows in rock crevices on slopes and near streams in the Maharashtra state. The seeds are used for therapeutic purposes, like treating diabetes or kidney stones. The leaves are used as plates by the local human populations who also consume the fruits as vegetables. Harvesting of the plant during its growth period for human needs is putting a lot of pressure on this species–especially since all parts of the plant are used and it, therefore, cannot propagate and reproduce. This plant is protected.

Communication
Vocalizations and body language allow langurs to communicate with one another. Infants in distress squeak and shriek. During altercations, displaying adult males issue loud calls or whoops. When it is time for the group to travel, adult males grunt bark or cough bark. To stay in touch, individuals honk, grunt, cough, or pant bark. They hiccup when they encounter members of another group. Adult males and sub-adult males vocalize with harsh barks when they spot a predator.

Females do not show any external signs of estrus, so when they are ready, they indicate their intention to start a family by shuddering their head and lowering their tail in the direction of the male that strikes their fancy.

Reproduction and Family
In most cases, the resident male in a uni-male/multi-female group or the dominant male in a multi-male/multi-female group fathers all the babies. The mothers are usually the highest ranking as well. Females give birth to one infant after a gestation period of approximately 200 days (almost 7 months). Newborns have black hands, feet, and face with some reddish highlights coming from the underlying skin that shows through their pelage. Infants are dependent on their mothers. They don’t walk or jump until they are two months old and are not weaned until they are 13 months old. They start vocalizing at six weeks of age. Females seem to share the care of infants, but, strangely enough, if a mother dies, her infant will die too as no other female will adopt the orphan. When a takeover occurs, infants are killed by the new dominant male.

Juveniles develop motor skills, social skills, and relationship-building skills by playing with each other. The playmates can be all males or a mix of males and females. They play fight by hitting, biting, and wrestling one another.

Photo Credit: Daniele Colombo/Flickr/ShareAlike License

Ecological Role
Black-footed gray langurs play an important role as seed dispersers. They also help other animals. For instance, deer eat food items that the langurs drop. The langurs’ alarm calls also help chital deer troops get on the move as soon as they are alerted to a predator’s presence by the monkey’s alarm calls.

Conservation Status and Threats
The International Union for Conservation of Nature classifies the black-footed gray langur as Least Concern (IUCN, 2015), appearing on the IUCN’s Red List of Threatened Species. The species is widely distributed with relatively few threats. Most of the threats are due to habitat loss and degradation. The nominate subspecies (Semnopithecus hypoleucos hypoleucos) is threatened as a result of hunting.

In the past, expanding timber plantations were threats; in the present and future, threats include agriculture, human settlement, fragmentation, habitat loss, mining, deforestation, hunting, deliberate fires, and local trade for live animals and meat for food and traditional medicine. Hunting is considered the most serious threat to the taxon.

These monkeys live in the Western Ghats, a region listed as a world heritage site for its rich biodiversity. It is also surrounded by one of the most densely populated areas in the world, so anthropogenic pressures are high. Forest degradation and loss of biodiversity date back to the British colonization era and have severely intensified since the 1990s. In fact, over 35% of the forest was lost and degraded between 1920 and 2013. In addition to deforestation caused by timber harvesting, logging, human settlements, and agriculture, several dams were built on the rivers that created water covered areas, contributing to even more habitat loss for the native plants species and animals of the region.

Natural predators include leopards, tigers, wolves, jackals, and pythons.

Conservation Efforts
The black-footed gray langur is listed on the Convention on International Trade in Endangered Species (CITES) Appendix I and Schedule II, Part II of the Indian Wildlife Protection Act. The state of Karnataka, where some of the black-footed gray langurs live, has its own People’s Biodiversity Registers and 16% of the forests within its jurisdiction are part of the Protected Area network.

Conservation efforts are needed to focus on habitat management, monitoring, and population assessments. Scientists agree that protecting fragmented forests is essential to preserve the gene pool of plants and animals they host, like the black-footed gray langurs.

​References:

  • ​“A Taxonomic Revision of the Langurs and Leaf Monkeys (Primates: Colobine) of South Asia” — Douglas Brandon-Jones – Zoos’ Print Journal 19(8): 1552-1554
  • “Distribution, status and conservation of primates of the Western Ghats” — Honnavalli N. Kumara and Mewa Singh
  • “Delineating Ecological Boundaries of Hanunan Langur Species Complex in Peninsular India Using MaxEnt Modeling Approach” — Nag Chetan, Karanth K. Praveen, Gururaja Kotambylu Vasudeva
  • Journal of Threatened Taxa / May 2019 – Vol 11 – No 7 – “The Importance of Conserving Fragmented Forest Patches with Hight Diversity of Flowrering Plants in the Northern Western Ghats:  An Example from Maharashtra, India” —  Amol Kishor Kasodekar, Amol Dilip Jadhav, Rani Babanrao Bhagat, Rakesh Mahadev Pawar, Vidya Shrikant Gupta & Narendra Yeshwant Kadoo. 
  • Journal of Threatened Taxa  / April 2015 – “Effect of Leaf harvesting on Reproduction and Natural Populations of Indian Wild Banana Ensete Superbum (Roxb) Cheesman (Zingiberales: Musacea) — Mahendra R. Bhise, Savita S. Rahngdale & Sanjaykumar R. Rahangdale
  • “Fauna of Karnakata – Zoological Survey of India” – edited by The Director, Zoological Survey of India, Kolkata (2013)
  • Monkeyland.co.za website – Gray Langurs
  • Flickr website – Monkey – Black-footed Gray Langur
  • Taxonomic Implications of a Field Study of Morphotypes of Hanunan Langurs (Semnopithecus entellus) in Peninsular India – K. S. Chetan Nag, P. Pramod, K. Praveen Karanth – International Journal of Primatology – DOI 10.1007/s10764-011-9504-0
  • Primate Behavioral Ecology – Karen B. Strier

Written by Sylvie Abrams, March 2020. Conservation status updated July 2020.