Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science ESTIMATING SLOTH BEAR ABUNDANCE FROM REPEATED PRESENCE-ABSENCE DATA IN NAGARAHOLE- BANDIPUR NATIONAL PARKS, INDIA By Arjun Mallipatna Gopalaswamy December 2006 Chair: Melvin Sunquist Major Department: Wildlife Ecology and Conservation It is notoriously difficult to estimate the abundance of bears in general and most methods that are currently available are too consumptive of time and effort. Sloth bears (Melursus ursinus) pose very similar challenges to field biologists trying to estimate their abundances. I investigated the possibility of estimating abundance of sloth bears using presence- absence data from repeated samples from camera traps. The simulation results generated from the likelihood estimator for small sample sizes showed a positive bias for A, the mean abundance per site. To more effectively use data with small sample sizes, a Bayesian approach to the problem was developed so that an informative prior could influence the parameter values to a reasonable range. A Bayesian Markov Chain Monte Carlo simulation procedure using the Gibbs sampler algorithm was developed. Data were analyzed using two ideas of bear movement that are incorporated into the model. Data were first analyzed with the intention of maintaining the idea of site independence to ensure that a bear will not occur in two sites during the sampling period. This restricted the data set and the uncertainties in the parameter estimates were found to be very high. To