On the Trail of the Sloth Bear
by Shyamala Ratnayeke
Page 1
: About the Sloth Bear
It is June at Wasgomuwa National Park. The rains have
ceased, and hot dry winds have parched the grass and dried
many of the smaller waterholes and streambeds. Many of the
elephants are still around, although by this time most herds
should have embarked on their yearly migration to Minneriya
and Giritale, where water and fodder are more plentiful.
Toward the south of the park, open plains of dry grassland
dotted with scrub and forest dominate the landscape. Across
the Wilmitiya plains, steep mountain escarpments form a
spectacular horizon. As one moves northward the habitat
changes to dense forest, most of it covering undulating
hills that grade into the steeper slopes of the Sudhukanda
range along the western boundary of Wasgomuwa. The elephants
and buffalo seem plentiful on the plains, the forest rich
with bird life, and one may see the occasional sambar. Less
obvious to either casual or seasoned visitors are the shy,
more nocturnal, jungle inhabitants who rarely make an
appearance. Who would imagine that this area is home to what
may possibly be Sri Lanka’s highest density of sloth
bears?
Sloth bears belong to the order Carnivora, a
highly eclectic group of mammals deriving from a common
predatory or flesh-eating ancestry. Modern Carnivora
are highly variable in dietary habits and modes of food
acquisition, ranging from committed flesh-eaters in the cat
family to the largely frugivorous ursids. The
Ursidae, or bear family, is a small group comprising
eight species distributed almost predominantly in the
Northern Hemisphere. The sloth bear (Melursus
ursinus) is found in India, Sri Lanka, Bangladesh, Nepal
and Bhutan. Sloth bears specialize on insects, especially
termites, which form a dietary staple, and possess special
morphological adaptations for myrmecophagy
(termite-eating): a broad extended palate, protrusible lips,
nostrils that can seal shut, a missing pair of middle upper
incisors, and powerful claws for digging.
The subspecies of the sloth bear (M. ursinus
inornatus) is endemic to Sri Lanka, and some anecdotal
evidence suggests that this bear may be somewhat
ecologically and behaviorally unique. The sloth bear is
listed as “vulnerable” by the IUCN, although data
on the bear’s population status for most of its range
is sketchy. There is general consensus, however, that
existing sloth bear populations, including those in Sri
Lanka, are becoming increasingly fragmented, that the bear
has disappeared from many areas of its former range, and
that sloth bear populations outside protected areas are very
likely decreasing or have disappeared entirely.
Shyamala Ratnayeke and her research team are on the
trail of the first six radio-collared sloth bears in Sri
Lanka. The study is a joint effort between the University of
Tennessee, the Open University of Sri Lanka, and the Sri
Lanka Department of Wildlife Conservation (DWLC), to learn
more about this rarely seen enigma of the Sri Lankan
jungles. The project on the sloth bear is supported through
the American Zoo and Aquarium Association, the U. S.
National Science Foundation and the University of Tennessee. Funding from the International Bear Association, the Chicago
Zoological Society and Sveriges Rovdjurscentrum-Orsa Grönklitt will enable the sloth bear study to continue in 2004.
Apart from Ratnayeke, the three main investigators include
Dr. Padmalal, a wildlife biologist and senior lecturer at
the Open University of Sri Lanka and Dr. Frank van Manen,
carnivore biologist at the University of Tennessee.
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Sloth Bear Caught on Remote Camera
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Page 2
: Telemetry as a Research Tool
Nowhere has telemetry revolutionized the field of wildlife science more than in the study of large solitary carnivores. One of the chief problems of studying carnivores is that most of them are solitary, highly mobile, and often nocturnal. Furthermore, many carnivore species are shy, tending to avoid areas used by human observers, and seeking cover in dense vegetation. The secretive nature of most carnivores tends to limit and bias the information gathered from studies that rely only on visual observation. Radio tracking techniques have been remarkably effective in reducing problems of studying elusive species, and have provided detailed information on the ecology and behavior of carnivores, of which very little was previously known. Telemetry can be used to follow known animals and collect behavioral and ecological data (e.g., movements, habitat use, activity patterns and social organization) without requiring constant visual observation of the animal concerned. The information obtained can be used in conjunction with existing geographic information systems (GIS) data to examine how natural and anthropogenic factors influence the bear's distribution and use of habitat, which in turn can serve to develop priorities for regional conservation.
Telemetry can also provide valuable information on survival and causes of mortality. For example, a mortality sensor on a radiocollar, or signs of prolonged inactivity from a radiocollared animal, can prompt a research biologist to approach the animal. If the animal has died recently, postmortem examination can often determine the cause of death, and whether it was human-induced or due to natural causes. If radiocollared animals have been shot illegally, an increase in patrolling and law-enforcement at strategic areas can be implemented.
Telemetry has aided park management in India’s Madhyar Pradesh in recent years. Madhyar Pradesh is home to most of India’s sloth bears and is also well-known for high frequencies of human-sloth bear conflict: within a five-year period in the early 1990s, 687 people were mauled by sloth bears, and 48 were killed. Radio tracking studies at Pannar National Park, Madhyar Pradesh, have thrown light on how human activities in the park (e.g., livestock grazing and firewood gathering) conflict with sloth bear activity patterns and habitat use. As a result, park managers have the information they need to ameliorate situations where human-sloth bear conflict is high.
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Female Sloth Bear Carrying Cub
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Page 3
: A Vulnerable Species
Both behavioral and life history characteristics of sloth bears seem to place them at special risk. Recent telemetry studies in India and Nepal indicate that sloth bears may require large areas of relatively undisturbed habitat for maintaining viable populations. Home range sizes are highly variable, averaging nine and fourteen square kilometers for males and females respectively in Royal Chitwan National Park, Nepal, to a minimum size of 40 square kilometers in Panna National Park, India. Area requirements for sloth bears appear to be largely dependent on food distribution and availability, emphasizing the need for more site-specific studies on the bear. Carnivores in general have relatively low reproductive rates, another factor that places their populations at risk, and the sloth bear is no exception. Sloth bear cubs may remain with mothers for 1.5 – 2 years, and females may take as long as three years or more between births.
In many parts of their range, sloth bears seem intolerant of human disturbance. Dave Garshelis, a noted international bear biologist, observed that sloth bears were either absent or occurred at very low densities in areas that had high levels of human disturbance. It appears that sloth bears do not adapt well to human encroachment, avoid areas with human activity, or interact aggressively with humans in areas where confrontation is highly probable.
Ratnayeke and her colleagues hope to fill some important gaps in knowledge of the Sri Lankan subspecies of sloth bear through their work at Wasgomuwa and also determine whether, and to what extent, sloth bears can tolerate different types of human disturbance. Without acquiring some fundamental knowledge about these bear populations, developing a sound conservation strategy for the survival of the bear, or identifying potential site-specific threats to its existence, is difficult. Also, by studying a healthy bear population, they hope to develop standardized quantitative techniques that can be reliably extended to other areas of the country to obtain indicators of relative abundance.
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Sloth Bear with Cub
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Page 4
: A Future for the Sloth Bear?
Can we assure a future for the sloth bear in Sri Lanka, and in doing so assure a future for other jungle inhabitants and, eventually, ourselves? In our efforts to conserve biological diversity, large carnivores such as the sloth bear play a key role as umbrella and flagship species. Be it fear, intrigue, hatred, or admiration, human beings have long been captivated by carnivores. Their sheer mobility, power, and predatory ability command fear and respect, and yet we know relatively little about carnivores. Possibly because of their essentially solitary or secretive nature, they remain elusive, mysterious and fascinating.
Most of us identify better with the loss of a species than with the loss of a population or the erosion of genetic diversity, and it is public support, after all, that forms the crux of most successful conservation efforts. The likelihood that the sloth bear is a species requiring large extents of relatively natural and undisturbed habitat to maintain viable populations makes it an ideal candidate for the role of an umbrella species—its intriguingly elusive and retiring nature, a potential flagship species—a symbol of Sri Lanka’s wilderness.
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 About the author:
Dr. Shyamala Ratnayeke is studying sloth bears and other
carnivores in two Sri Lankan national parks.
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