The sloth bear is thought to have evolved early in the Pleistocene Epoch (approximately 1,800,000 years ago). There are 2 subspecies: The Indian sloth bear Melursus ursinus ursinus and the Sri Lankan sloth bear Melursus ursinus inornatus.
The origin of their name isn't totally certain. One theory is that early explorers named them after seeing them hanging upside down from trees, similar to actual sloths. Another is that they were named after the slow wandering manner in which they walk.
The average range of females is 3 square miles, and the average range of males is about 5 miles. In the north eastern states of Assam and Mizoram, their range overlaps that of the Malayan sun bear. Also, at the base of the Himalayas, their range overlaps the range of the Asiatic black bear. Their present range is somewhat the same as it has been in the past. However, over time, they have become much more isolated to smaller, fragmented areas within that range.
Sloth bears have small ears, and they are not good at hearing nor seeing. However, like other bears, they have an excellent sense of smell. Male sloth bears can grow to be over 6 feet in length, measure 3 feet at the shoulders when standing on all four, and weigh from 175 to 310 pounds. Females are approximately 67 percent the size and weight of males.
The sloth bear's front legs are longer than its hind legs. Their front paws are turned inward and their toes are webbed together with the padding on the bottom of their paws. They have long, curved claws that are up to 3 inches long. All of these features are great assets when digging for ants and termites.
At early an age sloth bears lose their 2 front upper incisors, creating a very useful gap through which they can suck insects. To add to their sucking power, they have a long tongue, a concave palate, and can extend their lips beyond their nose. In addition, they are capable of closing their nostrils at will to prevent inhaling dirt when sucking up insects. The sloth bear makes so much noise sucking up insects that it can be heard up to 300 yards away.
Most sloth bears will run away when hearing and or smelling people. However, they will often become so focused on what they are doing that they don't notice the presence of others until they are encountered. When they feel threatened, they will often try to bluff their enemy by charging them, then stopping short, standing on their hind legs, roaring, and displaying their enormous claws. If this doesn't work, they will turn and run. Though they are not aggressive by nature, female sloth bears can be extremely vicious in protecting their young. Sloth bears can usually defend themselves quite well with their claws. Even though they are excellent climbers, they do not climb trees to escape danger. This is because some of its predators, such as the leopard, can climb trees just as well.
Like other bears, sloth bears are solitary animals except during breeding season and while females are raising their offspring. They are also nocturnal creatures in general. However, a female sloth bear with her offspring may often be seen at various times of the day to avoid nocturnal predators. They have no need to hibernate, but will retreat into caves or hollow tree trunks during long rainy periods.
Being excellent climbers, sloth bears will often climb trees to shake down fruit or invade a bee hive. Sloth bears can be committed when it comes to getting what they want. They will turn over rocks and logs and dig as deep as 5 feet to feed on large underground insect colonies. They will also continue eating honeycomb until it is completely gone, even when crying in pain from being stung by bees. Sloth bears do not fish, hunt, or graze.
After mating, the gestation period lasts from 6 to 7 months. The mother will then give birth to usually 2 cubs in a small underground cave. The weight of the hairless cubs averages between 10.5 and 17.5 ounces. They are blind at birth, and remain so for 2 to 3 weeks. The mother will remain in the cave with the cubs for the first 6 to 10 weeks, living mainly on her body reserves. When the time comes to leave the cave, the cubs will ride on their mother's back to and from the feeding grounds. The mother bear will usually carry her young in this manner for about 6 months, until they are almost a third her size. The cubs usually remain under their mother's care for 2 to 3 years.
Sloth bears in captivity have lived as long as 40 years. However, their average life span in the wild is thought to be closer to 20 years.