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Developing an empirical approach to optimal camera-trap deployment at mammal resting sites: evidence from a longitudinal study of an otter Lutra lutra holt

Findlay, Melanie; Briers, Rob; Diamond, Neil; White, Patrick

Authors

Neil Diamond



Abstract

The study of nocturnal mammals relies on indirect evidence or invasive methods involving capture and tagging of individuals. Indirect methods are prone to error, while capture and tagging mammals have logistical and ethical considerations. Off-the-shelf camera-traps are perceived as an accessible, non-intrusive method for direct data gathering, having many benefits but also potential biases. Here, using a six-year camera-trap study of a Eurasian otter holt (den), we evaluate key parameters of study design. First we analyse patterns of holt use in relation to researcher visits to maintain the camera-traps. Then, using a dual camera-trap deployment we compare the success of data-capture from each camera-trap position in relation to the dual set-up. Finally, we provide analyses to optimise minimum survey effort and camera-trap programming. Our findings indicate that otter presence and resting patterns were unaffected by the researcher visits. Results were significantly better using a close camera-trap emplacement than a distant. There was a higher frequency of otter activity at the holt during the natal and early rearing period which has implications for determining the minimum survey duration. Reducing video clip duration from 30 to 19 s would have included 95% of instances where sex could be identified, and saved 35-40% of memory storage. Peaks of otter activity were related to sunrise and sunset, exclusion of diurnal hours would have missed 11% of registrations. Camera-trap studies would benefit by adopting a similar framework of analyses in the preliminary stages or during a trial period to inform subsequent methodological refinements.

Citation

Findlay, M., Briers, R., Diamond, N., & White, P. (2017). Developing an empirical approach to optimal camera-trap deployment at mammal resting sites: evidence from a longitudinal study of an otter Lutra lutra holt. European journal of wildlife research, 63(6), Article 96

Journal Article Type Article
Acceptance Date Oct 6, 2017
Online Publication Date Nov 29, 2017
Publication Date 2017-12
Deposit Date Oct 30, 2017
Publicly Available Date Nov 30, 2018
Journal European Journal of Wildlife research
Print ISSN 1612-4642
Publisher BMC
Peer Reviewed Peer Reviewed
Volume 63
Issue 6
Article Number 96
Keywords camera-trap bias, methodology, monitoring, study design
Public URL http://researchrepository.napier.ac.uk/Output/1003465
Contract Date Oct 30, 2017

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