Searching for snares - How much effort is enough?

Abstract

The use of wire snares to hunt wildlife is prolific, particularly in the forests of Southeast Asia (1). Tackling this threat is a primary objective of law enforcement operations throughout protected areas, yet often efforts to remove snares are thwarted by a lack of information about hunter behaviour and an inability to detect snares. Even in areas of high snare abundance, rangers can spend many hours searching for snares with few results, eroding ranger morale, motivation and resources.

Understanding how best to allocate ranger search effort is of critical importance for protected area managers, especially in sites with exponential levels of snare hunting. Few studies systematically assess the factors that affect snare distribution (2), or explore efficiency in snare removal. Often studies rely on ranger-collected data through systems such as SMART. Whilst this data is undoubtedly useful for monitoring, data analyses typically fail to account for underlying biases, resulting in misleading conclusions being drawn.

Here we present a conceptual framework for evaluating the factors that influence snare detection by rangers. An experiment to calculate snare detectability in eastern Cambodia, carried out by Dr Hannah O'Kelly in 2011, achieved an average snare detection rate of about 30%, with variation between habitat and snare types. We introduce an experimental design which builds on that study (3), and aims to quantify how snare detectability varies with ranger search effort, whilst controlling for factors such as season, habitat, and ranger morale. We present our results, and detail the wider impact of the research for protected area management.

References

(1) GRAY, T.N.E., HUGHES, A.C., LAURANCE, W.F., LONG, B., LYNAM, A.J., KELLY, H.O., ET AL. (2017) The wildlife snaring crisis: an insidious and pervasive threat to biodiversity in Southeast Asia. Biodiversity and Conservation, 1–7.

(2) O’KELLY, H.J., ROWCLIFFE, J.M., DURANT, S.M. & MILNER-GULLAND, E. (2018) Robust estimation of snare prevalence within a tropical forest context using N-mixture models. Biological Conservation, 217, 75–82

(3) O’KELLY, H.J., ROWCLIFFE, J.M., DURANT, S. & MILNER-GULLAND, E. (2018) Experimental estimation of snare detectability for robust threat monitoring. Ecology and Evolution, DOI: 10.10, 1–8.