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Distribution
The species
M.ursinus is confined to the Indian sub-continent, while the subspecies
M.u.inornatus is endemic to Sri Lanka. In the Indian sub-continent, the sloth bear is found in the lowland forests and foothills of India, Nepal, and Bhutan, the northernmost periphery of its range extending from the terai of Nepal eastwards into Bhutan, Assam, Manipur and Arunachal Pradesh. In Sri Lanka it is distributed in the lowland forests of the northern, north central, eastern and southeastern regions, and absent in the hill country and the southwest.
Ecology
The sloth bear derives its name from a superficial resemblance to tree sloths, which are in fact much smaller mammals of the order Edentata. It is found in a wide variety of habitats such as grassland, thorn scrub, and dry evergreen forest, and is most numerous in the dry zone of Sri Lanka. Although it feeds on termites, its distribution in the wild is not strictly correlated with the abundance of termitaria. In the Uda Walawe National Park, despite the presence of numerous termitaria, the sloth bear no longer occurs. In Nepal, it was found that the sloth bear was either absent or occurred at low densities in areas with high termite abundance but also high human use. Because it is a large, relatively mobile carnivore, sloth bear can travel long distances in search of water, and is capable of detecting underground water sources in areas that are very dry. It can dig deep holes of 150-200 cm in dry streambeds to reach water. Such dug “waterholes” are also used by a variety of other mammals, insects and birds during the peak of the dry season. In this way, the sloth bear can have a far-reaching impact on a large component of the jungle community. In Sri Lanka, the jungle villager regards the sloth bear as the most dangerous animal, and few will disagree. Sloth bear has a poor sense of sight and hearing; thus, encounters with humans while foraging in the wild tend to be unexpected, and so it may sometimes react aggressively. An attack from a sloth bear usually involves loud vocalizations accompanying a charge, the impact of which usually knocks the victim to the ground. The attacks are usually short-lived and rarely fatal, but may cause severe mutilation to the victim’s head, for sloth bears typically maul the heads of their victims with their powerful canines.
The comparatively poor vision and hearing of sloth bears is compensated for by a highly developed sense of smell. It can be seen sniffing with its long, mobile snout during foraging or investigating the environment. Sloth bears are typically opportunistic omnivores, eating a large variety of plant and animal foods and switching their diet depending on the availability and abundance of various food items. They differ from all other ursids in having highly specialized morphological adaptations for myrmecophagy or feeding on ants and termites. Predictably, termites constitute and important dietary staple, although the amount consumed declines somewhat during the driest time of the year when foraging for them becomes harder. Apart from termites, sloth bear also feeds on larvae of bees, honey, and ants. Sloth bears are not accomplished predators, but may occasionally visit a carcass or scavenge a fresh leopard kill. Plant matter usually comprises fruit of
Cassia fistula (Ehela), Manilkara hexandra (Palu),
Drypetes sepiaria (Wira), Diospyros ovalifolia (Kunumella),
Nephelium longana (Mora), Szygium cumini (Damba) and
Zyziphus mauritiana (Eraminea). The sweet aromatic white flowers of
Madhuca longifolia (Mee) are a special favorite. Bears are especially fond of the sweet fruit of the Palu tree, and will climb trees when they are in fruit, using their powerful claws.
Adult sloth bears are usually solitary, except during the breeding season, but family units of a mother and small to almost-mature offspring are common. Several bears may sometimes occupy a single rock outcrop that has numerous shelters. There is no indication that sloth bears are territorial and marked shifts in home ranges may occur seasonally depending on the availability of critical resources, in particular food and water. In Sri Lanka, individual home ranges are small (3-7
km2).
Sloth bears can be rather noisy at times; their vocal repertoire includes roars, howls, screams, barks and squeals, associated with mating or fights with other bears. Reproductive rates of bears, in particular the sloth bears, are among the lowest for mammals. The onset of breeding is well advertised by whines and barks, which can be heard over considerable distance. Most observations on mating are in the latter part of the North East and beginning of the South West Monsoons. Gestation may last from 4-7 months and, similar to bears in temperate regions with highly seasonal environments, include a period of delayed implantation, a short gestation, followed by the birth of small, altricial cubs. The cubs are born blind, hairless and helpless, and are much smaller in proportion to the size of the mother than is the case with any other placental mammal. This trend is typical of ursids in temperate regions and seems to persist in tropical bears as well. In Sri Lanka females are most frequently seen with one cub, but a mother with two cubs is not uncommon.
Much of what we know of the life and reproduction of sloth bears in the wild comes from a capture and telemetry study in Nepal in the early 1990s. Pregnant females may dig their own dens in the ground or use natural hollows. After 9-10 weeks of confinement, during which the cubs are born, the female will emerge periodically to feed and cubs will accompany her for about a week or two later riding on her back. Sloth bear cubs tend to ride on their mother’s back almost continuously while traveling during the first few months. As they get older they may periodically descend to feed and play, but tend to ride routinely on mum’s back until they are about nine months old. This behavior is unusual for ursids and comprises a significant energetic cost for the mother to haul her cubs around who may sometimes exceed a third of her body weight. In captivity, sloth bears have lived up to 40 years although it is unlikely that wild bears survive that long. While the crude density of sloth bear in Nepal varies from an average of 0.25 per
km2 to a maximum of about 0.7 per
km2, in Sri Lanka estimates may exceed 1 per
km2 in prime bear habitat.
Conservation
Sea cows are often described as “floating meat-supplies”. In Sri Lanka, the dugong was once so plentiful that it was able to sustain commercial dugong fishery. Its meat is popular among the island’s Muslim community for whom pork is taboo. Dugongs yield between 25-50 litres of oil, and they are also prized for their alleged aphrodisiac properties. During the 1950s, between 100-150 animals were captured annually in Mannar District for their meat, oil and hide. So heavy was the cull that within a few decades, dugongs disappeared from much of their former range. Given their low reproductive rate, they are particularly vulnerable to over-exploitation. Today it is doubtful if a viable population survives in the northwestern waters of Sri Lanka. There is a very real risk that in the absence of strong conservation measures, the species might become extinct in the island. The indiscriminate exploitation in the past, the expansion of inshore fisheries are largely responsible for the endangerment of the species in Sri Lanka. With the intensification of offshore fisheries came the use of sophisticated nylon gill nets, resulting in increased accidental mortality of dugongs. The problem was further exacerbated by the use of mobile fishing gear, which like forest clear cutting, may not entirely eliminate biological activity, but promote the replacement of disturbance-intolerant equilibrial species by disturbance-tolerant opportunistic species.
For many years, the Wildlife and Nature Protection Society of Sri Lanka has called for the declaration of both the Dutch and Portugal Bays as marine sanctuaries for the dugong. These areas provide ideal conditions for the management of dugongs, as long as fishing is controlled, and the dynamiting of fish prohibited. The Puttalam lagoon is a suitable extension of such a marine sanctuary for the dugong. Ironically, until 27 February 1970, the dugong was officially regarded in Sri Lanka as “fish” and was not protected. Today however, it is a protected species. But legislation alone cannot protect the dugong in the absence of an effective law enforcement system. Ethics of conservation falls on deaf ears when people are poor. Reference
to the above material from:
©
Rukshan Jayewardene1, Iroshan Kulatunga2 and Charles Santiapillai3 (2003)
1
University of Maryland (USA)/University of Cambridge (UK) For the Leopard Trust
2
Dharmaraja College, Kandy, Sri Lanka
3
University of Peradeniya, Sri Lanka
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