Tufted Gray Langur, Semnopithecus priam
TUFTED GRAY LANGUR
Semnopithecus priam
Geographic Distribution and Habitat
Tufted gray langurs are endemic to the forests of southern India and Sri Lanka. The Western Ghats are a unique region of mountainous forests on the west coast of south India. This ecoregion has a range of forest types from dry deciduous to tropical. Most of the Indian gray tufted langurs live in these forests and form large troops in conservation areas. However, the increasing human population has resulted in the conversion of natural areas into agriculture and houses. So langurs have adapted to these non-native habitats and live in scrub forests with fewer trees, and even in some cities.
Sometimes we refer to the tufted gray langur as the Coromandal sacred langur or the Madras gray langur. These names have come about because of their native habitat along the Coromandel coast and in the city of Madras in India. In the Hindu religion, gray langurs are sacred because of their likeness to the monkey God Hanuman.
Taxonomists used to consider tufted gray langurs as one species with many variations (polytypic). Now, tufted gray langurs are categorized as two subspecies; one found in India (Semnopithecus priam priam) and the other in Sri Lanka (Semnopithecus priam thersites). Some researchers suggest that the differences between the subspecies are large enough to warrant a separate species classification.
In Sri Lanka, there have been reports of possible hybridization (young born from the mating of two different species) between purple-faced langurs (Semnopithecus vetulus philbricki) and tufted gray langurs (Semnopithecus priam thersites). Deforestation causes primate species to interact more, leading to rare occurrences of hybrid offspring. The new hybrid langurs look and behave differently from their parents. Hybrids make it difficult to study genetics and taxonomy, and conservation policies become harder to create without knowledge of behaviors and ecology.
The moniker priam in the tufted gray langur’s scientific name, Semnopithecus priam, is derived from King Priam of Troy, the legendary last king of Troy, famously known from Homer’s ancient Greek epic The Iliad. Biologists named three langur species after characters in The Iliad, but we don’t know why. Some suggest that the tufted gray langur’s characteristic crest resembles a crown and that is why it was named for the famous king.
Size, Weight, and Lifespan
Tufted gray langurs are fairly large monkeys (about the size of a toddler), measuring 22–31 inches (58.4–80 cm) from their head to the base of their tail. Their tail is longer than their body, measuring 26–40 inches (66–101.6 cm) long.
Adult males are usually easy to spot in the wild because they are significantly larger than adult females in a troop. Males weigh between 24 and 37 pounds (11–16 kg), while females weigh half that amount at about 19 pounds (9 kg).
These langurs can live between 18 and 25 years in the wild.
Appearance
Tufted gray langurs are large, pale, lanky monkeys with a characteristic tuft of light gray hair on their small head. They have a long, sturdy tail that they use as a rudder for balance. Their tails are hardly ever dragged on the ground. Instead, they hold their tail up, forming an s-shaped loop at the end.
They have long feet and legs and look quite graceful when they sit and pick through their food. Their faces are black and gray fur covers the rest of their body and tail. The gray-brown color becomes paler closer to the center of their body. We often see them looking around alertly with their large brown eyes as they forage.
There is a lot of variation in fur color between individual tufted gray langurs. But they are mostly pale with light brown-gray fur and pale hands and feet. Researchers have spotted rare melanistic forms of the tufted gray langur in the wild. These are individuals with dark, almost black fur throughout their bodies instead of the typical gray fur. Melanism is a genetic condition where the body makes more melanin (dark pigment in the body) and sometimes this condition randomly appears in the population.
Diet
These langurs are mainly folivores (leaf-eaters) and they eat a lot of mature leaves. The leaves are made of tough cellulose, which is difficult to digest (think about how much you have to chew when you eat a salad). The other challenge in digesting leaves is that leaves are lower in nutrients and energy-rich sugars, which means that langurs have to eat lots of leaves to get enough energy for their activities. To extract the maximum nutrition from leaves, tufted gray langurs have an enlarged fore-stomach that contains valuable gut bacteria that help digest the leaves.
Tufted gray langurs also supplement their diet with fruits, flowers, insects, and even tree bark and mud. One study found that the tufted gray langurs’ diet was made of 60% leaves, 20% twigs, and 18.87% fruits.
Though they eat leaves throughout the year, the other foods they eat depend on the season. In fruiting seasons, the langurs will shift their diet to more fruits and younger leaves. And during the drier seasons when vegetation has lower nutritional value, langurs will switch to consuming more insects.
Behavior and Lifestyle
Tufted gray langurs are diurnal, which means they are active during the day. They are considered semi-terrestrial because they spend most of their time on the ground and part of the time in the trees. Tufted gray langurs walk on all four limbs (quadrupedally) and, as they travel through the forest floor, they pick up morsels of food off the ground and climb lower tree limbs to feed on leaves. They usually feed from tree branches that are about 29 feet high (8.8 m). They also sometimes use a sideways leaping gait to jump up to trees or across branches.
These langurs are generally shy and wary of their surroundings. They like to hang out with other primates or herbivores because there is a better chance of spotting dangerous predators when there are more animals on the look-out.
Tufted gray langurs are semi-terrestrial and spend most of their time on the ground.
They are considered sacred in the Hindu religion.
They form mutualistic groups with axis deer to help keep watch for predators.
Their scientific name was inspired by the Greek epic, The Illiad. The crown of fur on the tufted gray langur’s head may have inspired the species name priam, based on the great King Priam of Troy.
A tufted gray langur’s day is mostly directed by how hot the tropical forest gets and how safe its feeding sites are. Once the troop wakes up, they start feeding on leaves in the early morning when the forest is still cool. When it gets too hot in the afternoon, the troop rests and settles down to groom and play. The rest helps avoid the heat and humidity, and it also gives the langurs time to digest their food. The leaves are full of fiber, which takes a lot of time to break down and digest. So, during afternoon rest times, the langurs do not actively eat. Instead, they digest their food for future energetic activities. Rest time is followed by another peak of feeding activity, where the langurs try to eat as much as they can before they sleep for the night.
Small troops are led by the largest, or the alpha, male and he often will direct the direction of travel for the whole troop. They maintain strict territories for the troop and the alpha male will defend the troop from other langur invaders. Alpha males have mating privileges over the females and all the juveniles will be his offspring. Once an alpha gets too old or weak to protect his troop, another male can take over the troop and mate with the females.
Larger troops are maintained by male-female hierarchies with females managing each other and the juveniles, while males take over the duties of patrolling and protecting the territory. Larger troops can have up to 3 adult males at a time.
Tufted gray langurs are vocal monkeys that depend on alarm calls, whistles, and grunts to maintain safety and order in the troop. A short cough-like sound is used to communicate tension to other langurs, a sort of “pay attention here” message. They also whistle to members that get separated to let them know where the main troop is.
Langurs have great eyesight and are usually looking around alertly for potential danger. Usually, one or two langurs in a troop will sit atop the canopy looking for signs of approaching raptors or leopards.
Langurs also spend time grooming each other for ticks and fleas. Grooming is a tactile form of communication that increases trust and affection between the groomer and groomed. And, as an additional benefit, the groomer gets some protein-rich snacks (i.e., ticks and fleas).
There is no breeding season for tufted gray langurs. Offspring are born year-round. Female tufted gray langurs are pregnant for about 6 months (168–200 days) and when the child is born, mothers carry them across their bellies for a long time, 13–20 months. Sometimes young langurs are almost half the length of their mother when they are carried, and when mothers run with their larger babies you can see two sets of tails trailing behind them!
They live in large troops with an average of 18 individuals (ranging between 5–60 individuals). Tufted gray langur troops are mostly made up of juveniles (average of 9 per troop) and females. The troops can tolerate more adult males (about 3 per troop) than other langur species, but usually there is only 1 adult male.
Families are usually affectionate and playful with each other, especially juveniles and females. The male takes on a more protective and aggressive role in the family, but will show signs of curious affection to his own newborns. Males tend to be aggressive to any langurs, even juveniles, outside of their own troop.
Langurs are a part of the complex forest food system. They are folivores that feed on mature leaves. This makes space for newer younger leaves on trees and allows more sunlight penetration to the forest floors. They also feed on fruits and can help disperse seeds away from the parent plant giving the seed the best chance at developing into an adult tree without competition. Langurs are an important part of the forest regeneration process.
Tufted gray langurs are also a food source for many different types of predators like tigers, leopards, black eagles, and rock pythons.
These langurs live peacefully with many primate species such as the Nilgiri langur (Semnopithecus johnii) in Kerala and the purple-faced langur in Sri Lanka. Tufted gray langurs have a varied diet and feed on leaves, which are a less-desirable food resource for other primates. These feeding behaviors drive competition down and allow different primate species to coexist together in a habitat.
Tufted gray langurs have an interesting mutualistic relationship with axis deer. Often, a troop of these langurs forages in the trees near herds of axis deer. Axis deer are alert creatures with a great sense of smell and, at the mere whiff of danger, they will emit loud warning barks that let everyone know that a predator is nearby. The langurs are one of the first to benefit from this warning and can escape into the canopy away from danger. Axis deer also benefit from foraging near langurs because langurs will often drop leaves and fruits. The deer can feed on foods that they would not otherwise have access to. Also, langurs have a birds-eye view of predators and will also send out an alarm call and warn the deer of predators.
The International Union for Conservation of Nature lists tufted gray langurs as Near threatened (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
The tufted gray langur is successful over much of their range in India, but in the more developed regions along the east coast of India and Sri Lanka, habitat destruction has changed their native forest habitat into scrublands and plantations.
Hunting and the pet trade are the biggest direct threats to the gray langur population, while habitat loss has indirect effects on the langur population. The ever-increasing human population creates fragmented forests, which reduces the food and space available for these langurs. This has exposed the langurs to the dangers of traffic and many have died in road accidents. Additionally, forest fragmentation increases human-wildlife interactions with langurs, which can make it easier for hunters to access the monkeys. Human-wildlife interactions also take place in agricultural lands where langurs raid crops and become habituated to the food sources at farms. Farmers view the langurs as a nuisance and will sometimes kill them to prevent further crop raids.
Other than hunting, well-intentioned people who feed these monkeys also create conservation problems. Wild monkeys who are fed by people can become aggressive and snatch food. These wildlife interactions often result in injured people. Authorities then have to deal with troublesome wild animals that have learned to get food by attacking people.
Tufted gray langurs are listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The Wildlife Act (1972) in India and the Fauna and Flora Protection Ordinance Act (No. 2, 1937) in South Africa give the tufted gray langurs national-level protection, which makes it illegal to hunt, capture, or trade them them.
In both countries, large conservation areas are protected from development and provide these langurs with continuous forest habitats (for example, Kalakkad-Mundanthurai Tiger Reserve in India and the Wilpattu National Park in Sri Lanka). When such large spaces are available, competition for food is less and tufted gray langurs can form large troops.
Governments have made some efforts to educate farmers to prevent killing these adaptable langurs, but more work needs to be done to educate the general public on the dangers and problems of feeding wildlife. There are action plans that outline protocols for dealing with troublesome monkeys that repeatedly attack humans for food; however, these management outcomes are not desirable and solve only the immediate problems of dangerous human-wildlife interactions. In these cases, the problematic monkeys are captured and kept in captivity because the relocation of tufted gray langurs to another forest is not a good option. Langurs need to stay in their troops to be successful and socially adjusted. Separating a langur from their family will only make the langur engage in problematic behaviors (like going into villages for food), or the monkey will not be able to survive in a brand-new habitat alone. Public outreach by authorities is the best way to prevent the need for dealing with problematic interactions.
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Written by Acima Cherian, June 2023