Inferring wildlife poaching in southeast Asia with multispecies dynamic occupancy models

Lucile Marescot,Arnaud Lyet,Olivier Gimenez,Neil Carter,Rohit Singh

doi:10.1111/ecog.04536

Abstract

Determining the ‘space race’ between co‐occurring species is crucial to understand the effects of interspecific interactions on the extinction risk of species threatened by poachers and predators. Dynamic two‐species occupancy models provide a flexible framework to decompose complex species interaction patterns, while accounting for imperfect detection. These models can describe poachers–wildlife interactions, as they allow estimating occupancy, extinction and colonisation probabilities of wildlife conditional on the occurrence of poachers and vice versa. We applied our model to a case study on wildlife poaching in the eastern plains of Cambodia. We used co‐occurrence data extracted from the database of the SMART partnership to study the distribution dynamics between poachers and six ungulate species pooled together into the tiger prey guild. We used four years of survey data reporting the locations of snares and of presence signs of the ungulates recorded by rangers during their monthly multi‐patrolling sessions. Our results showed that a substantial proportion of the sites occupied by ungulate species went extinct over the years of the study while the proportion of sites colonised by poachers increased. We also showed, for the first time, that spatio‐temporal heterogeneity in the patrolling effort explains a great deal of the variation in the detection of poachers and ungulates. Our approach provides practitioners with a flexible and robust tool to assess conservation status of species and extinction risk of wildlife populations. It can assist managers in better evaluating, learning and adapting the patrolling strategies of rangers.

Highlights

IntroductionIllegal hunting (hereafter poaching) is a major threat to wildlife species around the world (Gray et al 2018; Ripple et al 2016)
Illegal hunting is a major threat to wildlife species around the world (Gray et al 2018; Ripple et al 2016)
We found that detection probabilities were related to the spatial and temporal variations of patrolling effort (Table 2) whereas poachers’ occupancy was independent of wildlife distribution and unrelated to rangers’ patrolling effort (AIC = 3105.28, Table 3)

Summary

Introduction

Illegal hunting (hereafter poaching) is a major threat to wildlife species around the world (Gray et al 2018; Ripple et al 2016). Assessing the interrelationships between poachers and wildlife is notoriously difficult for various reasons, including: 1) inadequate information on the mediating influence of ranger patrols on poacher-wildlife interactions; 2) lack of empirical data on poachers, wildlife, and patrols at sufficient spatial and temporal resolutions; 3) imperfect detection of poachers and wildlife; and 4) the absence of statistical models to partition the influence of poachers, patrols, and wildlife on each other in space and time To help overcome these difficulties, we build upon a rapidly advancing class of occupancy models to study spatiotemporal interactions between poachers and threatened wildlife species in Cambodia. This study is part of a larger effort to use ecological theory and models to inform wildlife restoration efforts in this region, including the reintroduction of the globally endangered tiger (Panthera tigris)

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Results

Discussion

Conclusion