Evaluating methods to deter bats

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Bat deterrents, such as radar and acoustic methods have been suggested as potential mitigation for when bats are at risk of harm from human activities and/or structures. To date, no study has compared bat responses to these methods, for use in a European context. In this thesis, I aimed to (i) test acoustic and radar as potential deterrent devices, at foraging sites in the UK, (ii) determine the effect of an acoustic deterrent device with increasing distance and (iii) explore bat responses to an acoustic deterrent device and potential mechanisms for deterrence. I found that acoustic but not radar deterrents were effective at reducing bat activity at foraging sites and therefore I focussed on acoustic deterrents for the rest of the thesis. I developed a 2-dimensional (2D) thermal bat tracking system and used it in combination with acoustic and visual bat pass counting methods to examine bat responses to an acoustic deterrent with increasing distance. Results from a fine-scale study indicated an 80% reduction in bat activity at 15 m from the acoustic deterrent, reducing to 25% reduction at 30 m, but a larger scale experiment found no deterrent effect beyond 40 m. I then developed the thermal tracking method further and examined bat responses in 3D to deterrent broadcast and also examined the deterrent’s effect on echolocation call parameters. Bats increased their flight speed, decreased the tortuosity of their flight paths and focussed the signal of their echolocation calls into a reduced bandwidth, in line with a decrease in foraging behaviour and in support of the hypothesis that a masking effect of the deterrent sound affects echolocation behaviour. I conclude that acoustic deterrence shows great promise in the management and conservation of bat populations but warn that these methods should always be used with careful consideration and on a case-by-case basis.
Date of Award23 Jan 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorGareth Jones (Supervisor) & Marc W Holderied (Supervisor)

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