CHAPTER 3
 ESTIMATION OF SLOTH BEAR ABUNDANCE USING REPEATED PRESENCE-
 ABSENCE DATA IN NAGARAHOLE-BANDIPUR NATIONAL PARKS, INDIA

 Introduction

 The estimation of bear abundance involves many difficulties. Many expensive and labor-

intensive mark-recapture studies, most aided by telemetry, have been conducted on populations

of American black bears (Ursus americanus), brown bears (Ursus arctos) and polar bears (Ursus

maritimus) (Garshelis et al., 1999). Such studies are lacking for the other five species of bears

due to funding and logistical constraints. Furthermore, the density of these species is perceived to

be relatively low, thus making mark-recapture studies highly impractical.

 The only rigorous density estimate of sloth bears (Melursus ursinus) was derived by

Garshelis et al. (1999) during their study in Royal Chitwan National Park, Nepal. They used

information on bears seen in the company of radio-collared bears as a re-sight sample and

estimated bear density using the relatively simple, modified Peterson estimator (Bailey, 1952).

During the process of obtaining 3,117 radio-telemetry locations, they sighted 47 bears in the

vicinity of radio-collared bears, 42 of which had radio-collars on them. Using the modified

Peterson estimator, Garshelis et al. (1999) arrived at a density estimate ranging from 27 to 72

bears per 100 km2 depending on the season and habitat. It took investigators more than a year to

obtain a recapture sample of 47 accompanying bears, an effort that may be feasible only when

coupled with investigating other questions about sloth bear ecology that requires systematic and

repeated visits to the forest.

 Sloth bear densities are difficult to obtain by many conventional sampling methods. It is

not possible to identify sloth bear individuals from photographs obtained in camera traps, so

using a mark-recapture framework to determine densities, as done with tigers (Karanth &

Nichols, 1998), is not practical. Further, while conducting distance-sampling surveys along line