Estimating leopard density across the highly modified human-dominated landscape of the Western Cape, South Africa

Carolyn H Devens,Bool Smuts,Amy Dickman,Michael J Somers,Thulani Tshabalala,Jeannine S Mcmanus,Matt W Hayward

doi:10.1017/s0030605318001473

Abstract

AbstractApex predators play a critical role in maintaining the health of ecosystems but are highly susceptible to habitat degradation and loss caused by land-use changes, and to anthropogenic mortality. The leopard Panthera pardus is the last free-roaming large carnivore in the Western Cape province, South Africa. During 2011–2015, we carried out a camera-trap survey across three regions covering c. 30,000 km2 of the Western Cape. Our survey comprised 151 camera sites sampling nearly 14,000 camera-trap nights, resulting in the identification of 71 individuals. We used two spatially explicit capture–recapture methods (R programmes secr and SPACECAP) to provide a comprehensive density analysis capable of incorporating environmental and anthropogenic factors. Leopard density was estimated to be 0.35 and 1.18 leopards/100 km2, using secr and SPACECAP, respectively. Leopard population size was predicted to be 102–345 individuals for our three study regions. With these estimates and the predicted available leopard habitat for the province, we extrapolated that the Western Cape supports an estimated 175–588 individuals. Providing a comprehensive baseline population density estimate is critical to understanding population dynamics across a mixed landscape and helping to determine the most appropriate conservation actions. Spatially explicit capture–recapture methods are unbiased by edge effects and superior to traditional capture–mark–recapture methods when estimating animal densities. We therefore recommend further utilization of robust spatial methods as they continue to be advanced.

Highlights

The exponential growth of the human population is threatening all levels of biodiversity, including large carnivores, with % of species’ populations experiencing continuing declines (Estes et al, ; Ripple et al, )
Increasing human population density and loss of habitat increase the likelihood of resource competition with people, often resulting in human–carnivore conflict (Woodroffe, ; Cardillo et al, )
The spatially explicit capture–recapture density estimates varied by region and between regional phases, and estimates from secr were lower than those from SPACECAP

Summary

Introduction

The exponential growth of the human population is threatening all levels of biodiversity, including large carnivores, with % of species’ populations experiencing continuing declines (Estes et al, ; Ripple et al, ). Large carnivores are at risk of extinction because of their small population sizes, slow reproductive rates, complex social structures and requirement for large and contiguous habitats with sufficient prey (Cardillo et al, ; Ripple et al, ). These characteristics, and their vulnerability to negative interactions with humans, have driven declines of some of the most wide-ranging carnivores (Cardillo et al, ; Ray et al, ; Swanepoel et al, ; Wolf & Ripple, ). Persecution often includes indiscriminate use of lethal methods to manage livestock depredation by carnivores (e.g. snares, poisoned carcasses, gin traps (leg-hold traps), gun traps, live trapping) and targeted (often retaliatory) hunting (McManus et al, )

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Conclusion