Report from the Field: A Sloth Bear
Saga
by K. Yoganand
The huffing call brought my attention back to the den from
the pair of Bonneli's eagles soaring overhead. On that quiet,
mid-March evening in India’s Panna National Park, I was
peering into a den where a female sloth bear was resting with
her two cubs away from the day’s heat. This mother bear
had been radio-collared two years ago and named “80”
after the frequency of the transmitter fitted onto her. As
I waited on the ledge, “80” ambled out of the den
into my view and lay down at the entrance—apparently
still groggy from sleep. Her two cubs, three-and-a-half months
old then, followed her out of the den. Playing and tumbling
into each other, they looked like rolling balls of wool.
Sloth bears (Melursus ursinus), a tropical species adapted to feeding on ants and termites, are endemic to India, Nepal, and Sri Lanka, and occur commonly in Panna National Park, a scenic reserve in central India encompassing 210 square miles of dry deciduous forest. Panna has plenty of caves, crevices, and other forms of natural shelter along its long, steep, and bouldered escarpments. The bears use these as dens for resting and giving birth. With dense vegetative cover and water springs nearby, the escarpments provide an excellent habitat for sloth bears and other animals. Large carnivores such as tigers, leopards, and hyenas also use these dens, so sloth bear mothers like “80” must remain vigilant.
Laying down on her belly with her head resting on her front paw, the mother’s bare whitish muzzle and long white claws—used to dig out ant and termite nests—appeared bright in contrast with her black coat and the darkness of the den. The cubs crawled over her and climbed the surrounding rocks with an air of confidence, their safety assured by the watchful mother nearby.
Disturbed by one cub jumping on her, the mother turned around and huffed again. This sudden noise brought me back to my senses, having been lost in the wonder of this sloth bear kindergarten. After five years studying how sloth bears in Panna are reacting to a deteriorating habitat, moments like this justify all the trouble following these shy and secretive animals.
The bear species of the temperate and polar regions—American and Asiatic black bears, polar bears, and brown bears—give birth when they den up for the winter. For a tropical or subtropical species such as the sloth bear that does not face large seasonal changes or harsh winters, giving birth while denning may be a relic of the evolutionary past but provides a significant adaptive advantage even now. Sloth bear cubs require special protection, being born altricial—their eyes not yet open, their diminutive bodies barely furred. Dens provide security from predators to the cubs, as well as to the mothers themselves during nursing. Sloth bear dens can be as much as 50 to 60 F colder than outside. Resting inside dens helps the bears save considerable energy that they might otherwise have spent to cool themselves down.
Sloth bear mothers invest a great deal in the care of their offspring until the cubs disperse after two or three years. Mothers remain in the den with their cubs for up to two months, living on fat reserves and metabolic water during that period. Female “80,” having given birth to the two cubs in early December, remained inside the den until early February before venturing out to forage, while the tiny cubs remained inside the den. Then, when they were ten weeks old, the two cubs emerged from the den for the first time.
A sloth bear mother has a peculiar way of minding her cubs when foraging. She carries them on her back—piggybacking—a trait shared with other ant-eating mammals like the South American giant anteater (Myrmecophaga tridactyla). It is more efficient for one body, a little heavier with cubs on board, to move around than for three bodies to expend energy individually. The cubs hold on to their mother tightly and don’t fall off even when she charges at, or runs away from, a predator.
A mother needs to cover distances of up to five miles a day—staying active for eight to 14 hours—to find the scattered offerings of ants, termites, and seasonal fruits that comprise her diet. An abundance of such nutrients is also important for the survival of cubs during the crucial period of growth when they take to solid food. Later, cubs must generate fat reserves by feeding, in particular, on large quantities of fruits rich in sugar. Unfortunately, the fruits eaten by bears are also edible to people, and some fetch money in the market. Removal of fruits by local people could therefore affect the survival of cubs. Controlling this exploitation—regenerating fruit trees and improving habitat conditions for the bears—would greatly aid sloth bear survival.
Toward the end of March in Panna, sloth bears forage for mohwa flowers (Bassia latifolia), tendu fruits (Diospyros melanoxylon), and amaltas (Cassia fistula), in addition to ants and termites. These fruit trees are found in patches scattered throughout the forest, and so it requires a good knowledge of their territory for bears to find these seasonally varying food sources. During their extended upbringing, cubs have the opportunity to learn many things from their mothers, including how to find and remember reliable sources of food, as well as how to avoid and defend themselves from predators, how to react to the presence of humans, and how to find rest sites and maternity dens. Learning jungle skills is a continuing process with a lot of trial and error—but the cubs have an excellent teacher.
The cubs will stay with and learn from their mother for up to two and a half years before dispersing outside their natal territory or settling down alone on a portion of it. The cubs may eventually mate and reproduce, rear their own young, and live for up to 20 years. Or they might meet with an untimely demise.
It was the afternoon of May 10, and I had been waiting for the female “80” to emerge with her cubs from the cliff-side den in which they had been resting. Sloth bears are mainly nocturnal, and as the day’s light started to fade, “80” finally appeared from the den—but with only one cub.
The lone cub, now about 25 pounds (adult female sloth bears weigh at least 120 pounds, adult males as much as 310 pounds), jumped on top of its mother, held onto her fur, and lay down on her lower back. The two descended from the escarpment onto the lower plateau and moved from tendu tree to tendu tree, searching on the ground for fallen ripe fruits and gobbling them up. The cub got off its mother’s back to play and forage inquisitively among the small trees and rocks. After the mother finished feeding, the cub scrambled up her back from behind. As soon as they moved farther away, I climbed down to the den from my perch and looked inside for the other cub, or its remains. I found neither.
There are several possible explanations for the disappearance of the cub. It may have fallen sick and died. Or the mother may have had difficulty nursing both cubs and had to desert one. Or it may have been lost to predators. There is no dearth of predators in Panna, ranging from jackals and wild dogs to wolves, hyenas, leopards, and tigers. The tiger (Panthera tigris) is a threat even to adult bears; I have recorded several interactions between these two large carnivores in the last five years at Panna, including a sloth bear having been killed and eaten by a tigress and her cubs. Less likely, the cub may have been killed by a male sloth bear—if infanticide indeed occurs in sloth bears as commonly as in other bear species. Or the cub may have been killed by people.
Those people neighboring Panna have relied on the natural resources of the forest for ages, and some are still dependent on this habitat for their very livelihood. They graze cattle there, fell trees, gather fuelwood, or collect other products from nature’s bounty. Sadly, some are also destructive: They set the woods on fire to clear for agriculture, block bear dens, and even kidnap cubs.
Poaching of wild cubs to supply the performing bear market is a major—if largely overlooked—threat in India. The madharis, indigenous people who make a living exhibiting sloth bears and other small animals, train the cubs to dance and to collect money from people. Until the passage of a wildlife protection law a few decades ago that outlawed this practice, the madharis were issued licenses by the Indian government. They still travel around the country, carrying their old licenses and claiming that they have been breeding sloth bears and training their captive-born cubs to perform, rather than capturing wild bears.
Although the Smithsonian National Zoo has had exceptional success rearing sloth bear cubs, it is difficult to breed sloth bears even in the best of conditions provided by Western zoos. Presumably, the madharis really get their supply of sloth bears from the wild, where cubs are captured after their mothers are either killed or driven away. Though it would be easy to expose the madharis’ bogus claim, so far the Indian government has not done so.
In contrast with tigers, which can give birth to three or four cubs every two years, sloth bears give birth to either one or two cubs every three years on average. Capturing bear cubs even in small numbers thus poses a significant threat to the survival of sloth bear populations, which are considered vulnerable by the World Conservation Union. The process of such endangerment may have been unfolding before my eyes.
This family saga soon took another sad turn. On May 21, a bear mortally wounded a man in a valley frequented by people using the forest. The next morning, female “80” was found resting nearby. She appeared the likely culprit.
We knew one side of the story—that a bear had killed the man. But we could not know the other side, whether the man had provoked the attack by attempting to capture the mother’s cub. The next time I sighted “80,” on the evening of June 27, she was all alone. Her other cub had also disappeared, perhaps a victim of this earlier clash.
If so, this unfortunate episode illustrates how nature’s and humanity’s interests sometimes tragically collide. It need not be so. Forests such as those in Panna National Park play an essential role in the Earth’s ecosystems. They produce oxygen, act as watersheds, regulate microclimate, and perform other vital functions. In turn, animals keep the forests alive by pollinating flowers, dispersing seeds, and regulating tree density. These natural resources, if used sustainably, can offer people a means of long-term survival amid dire poverty. Biodiversity thus offers benefits that make its conservation profitable.
Another, less scientific but nonetheless noble reason for protecting natural spaces such as Panna National Park is that we want fascinating animals like the sloth bear to survive in order for cute bear cubs to play and piggyback on their mothers forever. Isn’t this alone a good enough reason for protecting their habitat?
MORE: A New Habitat for Sloth Bears
—K. Yoganand, who is pursuing a Ph.D. at the Wildlife Institute of India, is currently working on his dissertation at the National Zoo.
ZooGoer 30(6) 2001. Copyright 2001 Friends of the National Zoo. All rights reserved.
