N-mixture model-based estimate of relative abundance of sloth bear (Melursus ursinus) in response to biotic and abiotic factors in a human-dominated landscape of central India

Sankarshan Chaudhuri; Rajasekar Rajaraman; Sankar Kalyanasundaram; Sambandam Sathyakumar; Ramesh Krishnamurthy

doi:10.7717/peerj.13649

N-mixture model-based estimate of relative abundance of sloth bear (Melursus ursinus) in response to biotic and abiotic factors in a human-dominated landscape of central India

PeerJ. 2022 Dec 6:10:e13649. doi: 10.7717/peerj.13649. eCollection 2022.

Authors

Sankarshan Chaudhuri¹, Rajasekar Rajaraman¹, Sankar Kalyanasundaram², Sambandam Sathyakumar³, Ramesh Krishnamurthy^{1

4}

Affiliations

¹ Department of Landscape Level Planning and Management, Wildlife Institute of India, Dehradun, Uttarakhand, India.
² Salim Ali Centre for Ornithology and Natural History, Coimbatore, Tamil Nadu, India.
³ Department of Endangered Species Management, Wildlife Institute of India, Dehradun, Uttarakhand, India.
⁴ Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada.

Abstract

Reliable estimation of abundance is a prerequisite for a species' conservation planning in human-dominated landscapes, especially if the species is elusive and involved in conflicts. As a means of population estimation, the importance of camera traps has been recognized globally, although estimating the abundance of unmarked, cryptic species has always been a challenge to conservation biologists. This study explores the use of the N-mixture model with three probability distributions, i.e., Poisson, negative binomial (NB) and zero-inflated Poisson (ZIP), to estimate the relative abundance of sloth bears (Melursus ursinus) based on a camera trapping exercise in Sanjay Tiger Reserve, Madhya Pradesh from December 2016 to April 2017. We used environmental and anthropogenic covariates to model the variation in the abundance of sloth bears. We also compared null model estimates (mean site abundance) obtained from the N-mixture model to those of the Royle-Nichols abundance-induced heterogeneity model (RN model) to assess the application of similar site-structured models. Models with Poisson distributions produced ecologically realistic and more precise estimates of mean site abundance (λ = 2.60 ± 0.64) compared with other distributions, despite the relatively high Akaike Information Criterion value. Area of mixed and sal forest, the photographic capture rate of humans and distance to the nearest village predicted a higher relative abundance of sloth bears. Mean site abundance estimates of sloth bears obtained from the N-mixture model (Poisson distribution) and the RN model were comparable, indicating the overall utility of these models in this field. However, density estimates of sloth bears based on spatially explicit methods are essential for evaluating the efficacy of the relatively more cost-effective N-mixture model. Compared to commonly used index/encounter-based methods, the N-mixture model equipped with knowledge on governing biotic and abiotic factors provides better relative abundance estimates for a species like the sloth bear. In the absence of absolute abundance estimates, the present study could be insightful for the long-term conservation and management of sloth bears.

Keywords: Camera trap; Human-dominated landscape; N-mixture model; Relative abundance; Sloth bear.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Forests
Humans
India
Poisson Distribution
Sloths*
Ursidae* / physiology

Grants and funding

This work was supported by the Madhya Pradesh Forest Department, Madhya Pradesh, India. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.