Sloth bears have shaggy, dusty-black coats; pale, short-haired muzzles; and long, curved claws which they use to excavate termites and ants. A cream-colored crescent usually marks their chests. Their shaggy fur does not have an undercoat, so it is relatively cool, and protects them from tropical insects. Sloth bears' nostrils can close completely, protecting the animals from dust or insects when raiding termite nests or beehives. Despite this, they have a keen sense of smell, as well as eyesight similar to that of humans.
Adult sloth bears are missing their two front (incisor) teeth enabling them to suck up termites and other insects with ease. Sloth bears have the largest canines with respect to body size of any bear.
It is thought that their feet are turned inward to increase digging efficiency.
The first valid scientific description of this species, by George Shaw in 1791, called it Ursine (meaning bearlike) bradypus (literally, slow foot and the genus name of three of the species of sloths). Shaw thought that the bear was a sloth, primarily based on the shared characteristic of lacking the first upper incisors. Time, and additional specimens, eventually revealed the true taxonomic relationships, but the confusing common name remains.
Sloth bears grow 5 to 6 feet (1.5 to 2 meters) long, stand 2 to 3 feet (0.5 to 1 meters) high at the shoulder, and weigh, on average, 200 to 300 pounds (90 to 140 kilograms). Sloth bears are the least sexually dimorphic of all bears.
Sloth bears live in a variety of dry and moist forests and in some tall grasslands, where boulders and scattered shrubs and trees provide shelter. Their range includes India, Sri Lanka and southern Nepal. They have also been reported in Bhutan and Bangladesh.
Sloth bears are noisy, busy animals. They grunt and snort as they pull down branches to get fruit, dig for termites and ants, or snuffle under debris for grubs and beetles.
If threatened, they will stand on two legs, brandishing their clawed forepaws as weapons. Their large canines are used for defense against tigers. Other potential predators include jackals, wild dogs, wolves, leopards and other Asian bear species.
As animals who consume ants, sloth bears are considered myrmecophageous.
When trees are in fruit, usually during the monsoon season, sloth bears dine on mango, fig, ebony and other fruits, and also on flowers. Termites, dug out of their cement-hard nest mounds, and some ants, are year-round staples. During non-fruiting season, insects constitute 95 percent of their diet. Sloth bears climb trees and knock down honeycombs, later collecting the honey from the forest floor. Beetles, grubs, and other insects round out their diet. During food shortages, sloth bears will eat carrion. They also sometimes raid farm crops.
The Smithsonian's National Zoo's sloth bears eat a dry-food mixture designed for omnivores plus fruits such as oranges, melons, and grapes. At the Zoo, they are offered food three times daily: a morning meal and afternoon snack outdoors plus an evening meal indoors. They also receive treats such as mealworms, crickets, nuts, vegetables and honey as enrichment.
In India, sloth bears breed in late spring to early summer. In Sri Lanka, however, there is no seasonality to sloth bear breeding. Mating occurs over several days to weeks and is very noisy. Several copulations are necessary to induce ovulation in the female.
While embryonic development takes only two months, gestation lasts four to seven months if there has been delayed implantation. In the weeks to months before a birth, the female may exhibit "denning" behavior. She digs a den or prepares space in a cave. She may become less interactive, or easily agitated, disinterested in food, defend the cubbing area, and sleep more. These behaviors, correlated with hormonal changes, may occur even if the bear is experiencing a pseudo-pregnancy.
In the North American zoo population, births generally occur in late December to early January. One or two cubs (rarely three) are born in each litter in an underground den. They are born weighing about 1 pound (2 kilograms), open their eyes at about two to three weeks and start to "walk" around 4 weeks. After emerging from the den at around 9 to 12 weeks, cubs stay with their mother for approximately two to three more years before heading off on their own. Cubs will nurse for two to three years, which is long relative to other bears. Sloth bears are the only bears to routinely carry young on their backs; the cub clings to the extra shag of fur ("saddle") on the mother's back until it is 6 to 9 months old. All animals that consume primarily ants put their young on their backs, sloth bears included. They are the only bears to routinely carry young on their backs.
Sloth bears are sexually mature at age three, but are rarely mothers until later in life. They breed once every three years, more often if they have not given birth or have lost their cub or cubs. Sloth bears exhibit low fecundity and high infant mortality. Fifty-three percent of males and 38 percent of females die as cubs.
These bears adapt their sleep/wake cycle to their environment and may be on a nocturnal, diurnal or crepuscular schedule depending on how many other bears, people, or predators are in their habitat. In protected areas, for example, they may be more active during the day. Sloth bears are active for about eight to 14 hours each day, and they will not hibernate.
Sloth bears in human care generally live into their 20s. The oldest recorded male in the North American Species Survival Program population lived to 29; the oldest recorded female lived to 36.
About 20,000 or fewer total sloth bears remain in the wild. However, no reliable large-scale population survey has been conducted. It is estimated that their population has declined by 30 to 49 percent in last 30 years mainly because of habitat loss, but also because of poaching for parts, capture for trade and elimination as pests. Habitat is being transformed into human settlements, agriculture, plantations of teak and eucalyptus and fuel wood and timber.
Once abundant, sloth bears have steadily lost ground due to habitat destruction and fragmentation, hunting, and capture. One hundred years ago, their world was very different; extensive habitat remained, human settlements were scattered, and relatively few bears were hunted. Today, they inhabit one of the world's most crowded regions. Poachers kill bears to harvest their gall bladders and other parts for use in traditional Asian medicine. The bile from their gall bladders is used in shampoo, eye drops, wine and medicine thought to cure heart disease, improve eyesight, and decrease high blood pressure. Bear bile sells on the black market at $2 million for 5 kilograms—as much as heroin. The same substance, ursodeoxycholic acid, can be produced in the laboratory and this synthetic version has proven to be a safer and more humane alternative for medical use.
Other sloth bears are captured for use as sideshow animals called "dancing bears." Until recently, approximately 100 cubs were taken from the wild annually for this purpose. The mother is killed in the process of poaching the cubs, their teeth are removed and a metal ring is inserted into their muzzle with a rope tied on the end. When the rope is pulled, the bear stands up in pain and "dances." Despite a ban on this practice since 1972, it was difficult to control because the dancing bears were the primary source of income for the Kalandar tribe. Today, most of the dancing bears have been rescued thanks to organizations like Wildlife SOS and WSPA-Wildlife Trust of India. These organizations provide education and career training for tribe members in exchange for giving up their bears and agreeing to never again poach wildlife, thus ensuring a better life for both the humans and the bears.
In Pakistan, some people participate in "bear-baiting," the practice of having bears fight dogs. Sloth bears are poached from India and smuggled over the border for this practice. Farmers also kill bears that raid their sugarcane or cornfields. Sloth bears are now common only in parks and other remaining national forests. Strict protection of both bears and their forest and grassland ecosystems are their best hope for the future.
Zoo scientists are engaged in a wide-ranging set of studies in support of the conservation of the endangered sloth bear in the wild in India. As far back as the early 1970s, John Seidensticker and his colleague Andrew Laurie were the first scientists to study sloth bears in the wild, in Nepal. Fifteen years later, Anup Joshi and his University of Minnesota advisors David Garshelis and David Smith, all Smithsonian Research Associates, took up the challenge of studying these bears in Nepal. At present, A.J.T. Johnsingh and K. Yoganand are studying sloth bears in central India. Johnsingh, who worked with Seidensticker in 1981 as a post-doctoral fellow, is head of the wildlife faculty at the Wildlife Institute of India. K. Yoganand was his graduate student; he is now a Friends of the National Zoo-supported post-doctoral fellow at the Zoo.
The Zoo will continue training local students and future conservation leaders while studying the ecology, behavior and physiology of sloth bears in support of their conservation. Sustaining threatened wild sloth bear populations can be achieved only with a comprehensive understanding of their ecological and behavioral needs.
Zoo scientists are also studying the behavior, welfare and cognitive abilities of sloth bears in captivity. Headed by animal care staff, these studies will help improve captive management of bears and help to reduce some of the abnormal or stereotypical behaviors often seen in zoos.
One sloth bear currently lives on Asia Trail—a female named Remi.