Abstract:
The study focused on the endangered Sri Lankan sloth bear (Melursus ursinus
inornatus), assessing its habitat preferences through occupancy modeling to improve
target conservation efforts in protected areas. The study was conducted in Wilpattu
National Park from September 2024 to April 2025 during the wet season. Twelve
passive infrared camera traps were installed using a systematic-random sampling
method and relocated every 1.5 months. Data on sloth bear presence/absence and
habitat variables, including vegetation, physical, and food abundance covariates,
were collected. Occupancy was analyzed using a likelihood-based method, with
detection histories recorded as binary values ('1' for presence, '0' for absence),
assuming camera trap station independence and no animal movement between
stations. Logistic regression identified significant covariates, and highly collinear
ones (r > 2) were excluded to avoid overfitting. Data analysis was performed using
the PRESENCE software, where detection histories were combined into single
species models. Multiple models incorporating various covariates were developed to
assess their impact on occupancy. Model selection was based on delta AIC (dAIC),
with model-averaged parameters used to estimate occupancy and detection
probabilities. Occupancy probabilities for different habitat types were calculated and
visualized using R Studio 4.5.0. The occupancy probability of sloth bears was highest
in dry mixed evergreen forests (0.93) and tropical thorn forests (0.68), with grasslands
showing the lowest probability (0.30). The best-fitting model for occupancy had an
AIC weight of 0.11, with a model-averaged occupancy probability of 0.79, compared
to a naïve estimate of 0.49. Main factors influencing sloth bear occupancy include
stem density>10cm, litter depth, termite mound density, and fruiting tree density, all
of which positively impact occupancy. The negative impact of distance to water
bodies highlights the importance of key habitat features for conservation. Focusing
on areas with essential resources, such as water and food, can improve habitat
management and ensure the long-term survival of sloth bears.
