Many people think of a monkey as a cute, brown, fuzzy primate that uses vines to swing from tree to tree. But I bet you didn't know that there are actually more than 250 different species of monkeys in the world. They are divided into two groups: Old World monkeys that are native to Africa and Asia (like langurs), and New World monkeys that are indigenous to the Americas.
But their homes aren't the only reasons they differ. New World monkeys consist of almost exclusively tree-dwelling species, while Old World monkeys spend much of their time on the ground. New World monkeys also have prehensile tails, meaning they can use their tails to grasp or hold onto objects — balance and support that comes in pretty handy when they're moving among the trees. Meanwhile, Old World monkeys also have tails (in fact, langur is a Hindi word meaning "long tail"), but they lack the ability to grasp objects.
"Tails that truly grip are known as prehensile tails, and these are unique to New World monkeys," says Dean Gibson, curator of primates for San Diego Zoo Global, via an email interview. "Though langurs' slender tails are rather long, their tails aren't prehensile. They do come in very handy for balance when moving around the canopy of their jungly habitat, though."
Langurs belong to a species of Old World monkey of the subfamily colobinae found throughout Southeast Asia and Southern China, as well as parts of India. "This group contains more than 60 species, all of them distinguished by their leaf-rich diet," says Gibson, a wildlife biologist who has more than 40 years of experience working with primates." Here are six fun facts about this unique monkey:
1. They Have a Complicated Digestive System
Unlike New World monkeys, which feed mostly on fruit, the langur feeds largely on leaves and other parts of plants, including bark, buds and seeds, and, yes, some fruit, says Gibson. Many even have special stomachs (sometimes with a potbellied appearance) that enable them to better break down the cellulose found in plants. "Unusual for a primate, langur digestion is similar to a ruminant's," says Gibson. "They have multi-chambered stomachs that host bacteria that help digest the plant cellulose in their leafy diet. Bacteria in their foregut prime tough plant matter, so that more nutrients can be absorbed by the gut later in the digestive process."
2. And Speaking of Digestion ... They Sure Can Burp
You can tell if their stomach is working when you hear them burp. "They burp a lot," says Gibson, "and it is not a pleasant odor!"
3. Langurs Vary in Color from Species to Species
"Gray and black are more common, as are shades of orange and gold," says Gibson. "Youngsters can be a very different hue from adults. Known as neonatal coat coloration, the color is thought to help the young be identified for protection by their troop." Many langurs, she adds, also are characterized by pointed hair around their face and head.
4. They Come in All Shapes and Sizes
Langurs run the gamut when it comes to size and physical characteristics, from the long nose of the proboscis monkey (nasalis) to the back end of the pig-tailed langur (simias). "Each species of langur has its own characteristic, but at the San Diego Zoo, our Francois' langurs stand out for the white stripes on each side of their mouth, their white-tipped tail and pointy tuft of fur atop their head," says Gibson. "For the general public, the douc langurs (pygathrix) would likely take the prize for beauty."
5. They Are Fairly Passive and Friendly
"Langurs generally co-exist peacefully with people," says Gibson. "They are territorial, however, and aggression does play a role in establishing social order."
6. Some Species Are Endangered
"And some face a very real threat of extinction," says Gibson. "On the whole, langurs face a variety of threats from human encroachment across their various ranges. Hunting, habitat destruction and illegal wildlife trafficking are ever-present dangers for these monkeys. The IUCN Red List is a good resource regarding the status of each species."