Detecting wildlife poaching: a rigorous method for comparing patrol strategies using an experimental design
NIC K VAN DOORMAAL,A.M.LEMIE UX ,S TIJN RUITER PAUL M. R. R. ALL IN and CRAIG R. S PEN CER
Abstract Many studies of wildlife poaching acknowledge the challenges of detecting poaching activities, but few ad- dress the issue. Data on poaching may be an inaccurate re- flection of the true spatial distribution of events because of low detection rates. The deployment of conservation and law enforcement resources based on biased data could be in- effective or lead to unintended outcomes. Here, we present a rigorous method for estimating the probabilities of detecting poaching and for evaluating different patrol strategies. We illustrate the method with a case study in which imitation snares were set in a private nature reserve in South Africa. By using an experimental design with a known spatial dis- tribution of imitation snares, we estimated the detection probability of the current patrol strategy used in the reserve and compared it to three alternative patrol strategies: spa- tially focused patrols, patrols with independent observers, and systematic search patterns. Although detection prob- abilities were generally low, the highest proportion of imita- tion snares was detected with systematic search strategies. Our study provides baseline data on the probability of de- tecting snares used for poaching, and presents a method that can be modified for use in other regions and for other types of wildlife poaching.
Keywords Detection probability, evaluation, experimental design, law enforcement, patrol strategies, poaching, snares, South Africa
Introduction
espite considerable conservation efforts,wildlife poach- ing is an increasing problem in many protected areas (UNODC, 2016; Ripple et al., 2019). Deterring
D NICK VAN DOORMAAL*† (Corresponding author,
orcid.org/0000-0002-8947-
4944), ANDREW M. LEMIEUX and STIJN RUITER*(
orcid.org/0000-0003-2872- 2710) Netherlands Institute for the Study of Crime and Law Enforcement, P.O. Box 71304, 1008 BH, Amsterdam, The Netherlands E-mail
nick.vandoormaal@
gmail.com
PAUL M. R.
R.ALLIN andCRAIG R. SPENCER Transfrontier Africa NPC, Hoedspruit, South Africa
*Also at: Department of Sociology, Utrecht University, Utrecht, The Netherlands †Current address: Transfrontier Africa NPC, Hoedspruit, South Africa
Received 25 February 2020. Revision requested 18 May 2020. Accepted 10 November 2020. First published online 30 June 2021.
poaching activities through detection and apprehension is a core responsibility of law enforcement rangers (Hilborn et al., 2006; Dobson et al., 2019). Rigorous evaluations of pa- trol efforts are needed to examine whether they are effective in reducing poaching, and to inform decision-making. Such evaluations usually involve analysing data collected by ran- ger patrols (Stokes, 2010; Burton, 2012; Johnson et al., 2016), but are often hindered by data scarcity, inaccuracy and bias (Gavin et al., 2010; Keane et al., 2011). Wildlife poaching is a complex
problem.Most poaching
activities can only be identified through proactive and reac- tive patrolling, and levels of poaching in unpatrolled areas remain unknown (Critchlow et al., 2015). Even in areas that are subject to ranger patrols, some illegal activities may go undetected. Previous studies have shown that de- tectability of evidence for wildlife poaching can vary with le- vels of experience of patrol staff, the quality and quantity of available information, and between landscapes and seasons (Wato et al., 2006; Becker et al., 2013; Linkie et al., 2015; Rija, 2017;O’Kelly et al., 2018; Ibbett et al., 2020). In addition, for patrol data to be valuable, rangers need to report their ob- servations accurately. Potential reasons for not reporting include equipment failure, inability to use the recording equipment correctly, forgetting to record observations, lack of supervision in the field, or collusion with poachers. The observations recorded by rangers are thus influenced by the patrolling efforts themselves, rather than being solely a function of where actual poaching activities occur (Moreto et al., 2014). If biased or inaccurate data are used to guide patrol strate-
gies, patrol efforts may not be targeted in areas where they are most needed. For example, deterrence of poachers by rangers can confound inferred trends on the occurrence of illegal activity (Dobson et al., 2019). In addition, recorded poaching events are often used to inform decisions on future deployment of rangers (Johnson et al., 2016; Critchlow et al., 2017). Rangers are trained and experienced in searching for illegal activities, but their perspectives and training could potentially exacerbate the biases in recorded data. For ex- ample, a previous study showed that rangers avoided certain areas during their patrols, which influenced the observed poaching patterns (Kuiper et al., 2020). Although rangers play a crucial role in the security of protected areas, patrol- based data should be used with caution to avoid relying on inaccurate poaching patterns, which can lead to inefficient
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (
http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Oryx, 2022, 56(4), 572–580 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605320001301
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