On the tiger trails: Leopard occupancy decline and leopard interaction with tigers in the forested habitat across the Terai Arc Landscape of Nepal

Kanchan Thapa,Sabita Malla,Samundra Ambuhang Subba,Gokarna Jung Thapa,Babu Ram Lamichhane,Naresh Subedi,Maheshwar Dhakal,Krishna Prasad Acharya,Madhuri Karki Thapa,Pramod Neupane,Shashank Poudel,Shiv Raj Bhatta,Shant Raj Jnawali,Marcella J Kelly

doi:10.1016/j.gecco.2020.e01412

Abstract

Better conservation planning requires updated information about leopard distribution to prioritize and allocate limited resources available. The long-term persistence of leopards and sympatric tigers can be compromised by linear infrastructure development such as roads that fragment habitat. We used detection and non-detection data collected along walking search paths (~4140 km) in 96 grid cells (each cell 15 km by 15 km) spread across potential habitat (~13,845 km2) in the Terai Arc Landscape, Nepal. Multi-season occupancy models allowed us to make both spatial and temporal inferences between two surveys in 2009 and 2013, based on ecologically relevant covariates recorded in the field or remotely sensed. Additionally, we used 2013 data to make inferences on co-occurrence between tigers and leopards at the landscape level. We found the additive model containing deforestation and district roads negatively influenced leopard detection across the landscape. Although weak, we found anthropogenic factors such as extent of deforestation (decrease in forest cover) negatively affected leopard occupancy. Road abundance, especially for the east-west highway and district roads, also negatively (but weakly) influenced leopard occupancy. We found substantially lower occupancy in the year 2013 (0.59 (SE 0.06)) than in 2009 (0.86 (SE 0.04)). Tigers and leopards co-occurred across the landscape based on the species interaction factor (SIF) estimated at 1.47 (0.13) but the amount of available habitat and the prey index mediated co-occurrence. The SIF decreased as habitat availability increased, reaching independence at large habitat patches, but leopard occupancy declined in sites with tigers, primarily in large patches. The prey index was substantially lower outside of protected areas and leopards and tigers co-occurred more strongly in small patches and at low prey indices, indicating potential attraction to the same areas when prey is scarce. Mitigation measures should focus on preventing loss of critical leopard, tiger, and prey habitat through appropriate wildlife-friendly underpasses and avoiding such habitat when building infrastructure. Leopard conservation has received lower priority than tigers, but our metrics show a large decline in leopard occupancy, thus conservation planning to reverse this decline should focus on measures to facilitate human-leopard coexistence to ensure leopard persistence across the landscape.

Highlights

There is increasing evidence that large carnivore populations can thrive in multi-use landscapes (Banerjee et al, 2013; Odden et al, 2014)
Our results indicate that a) leopard occupancy declined by 31% between 2009 (Psi: 0.86) and 2013 (Psi: 0.59), b) leopard detection was strongly, negatively influenced by deforestation and district roads, c) anthropogenic factors such as disturbance, road network, and extent of deforestation appear to be negatively affecting occupancy across the landscape, but effects were generally weak or inconclusive; d) tigers and leopards tend to co-occur across the landscape but this interaction is mediated by extent of available habitat and prey index, in slightly different ways inside and outside protected areas
This study is the first of its kind to analyze leopard occupancy along the spatially replicated transects designed for tigers and leopard interactions with a congener at the landscape level

Summary

Introduction

There is increasing evidence that large carnivore populations can thrive in multi-use landscapes (Banerjee et al, 2013; Odden et al, 2014). The leopard (Panthera pardus fusca) and the tiger (Panthera tigris tigris) are the dominant predators in the lowlands of Nepal (Thapa et al, 2014) They share habitat and influence trophic community structure in terrestrial ecosystems in Nepal (Wegge et al, 2009); India (Harihar et al, 2011); Bhutan (Wang and Macdonald, 2009); and Thailand (Simcharoen et al, 2018). Information on leopard distribution and its determinants is critical for setting conservation priorities for the species (Scott et al, 2002; Jathanna et al, 2015) The leopard typifies this critical requirement for site-specific conservation planning, to adequately prioritize and allocate resources for human-wildlife conflict resolution and habitat protection measures across human-dominated areas

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