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RESEARCH ARTICLE
Contents Vol 35(4)

Aerial mark–recapture estimates of wild horses using natural markings

Michelle J. Dawson A C and Cameron Miller B
+ Author Affiliations
- Author Affiliations

A Institute for Applied Ecology, University of Canberra, Canberra, ACT 2601 Australia.

B Parks Victoria, Level 9, 535 Bourke St, Melbourne, Vic. 3000, Australia. Present address: SMEC Australia, Level 5, 71 Queens Parade, Melbourne, Vic. 3004, Australia.

C Corresponding author. Email: wildeye@netspeed.com.au

Wildlife Research 35(4) 365-370 https://doi.org/10.1071/WR07075
Submitted: 27 June 2007  Accepted: 23 January 2008   Published: 27 June 2008

Abstract

Aerial mark–recapture population estimates utilising the natural markings of wild horses to identify individuals was applied in the Bogong High Plains, Alpine National Park, Victoria. A discrete population of wild horses occupying an area of 180 km2 was sampled over two days in 2005. This study explored the feasibility of a technique that aimed to enable managers to estimate the size of the horse population and monitor it over time. Four observers (including the pilot) searched for horses from a helicopter. Once horses were sighted, photographic and written observations were used to ‘mark’ each animal. The survey was repeated the following day with observations ‘recapturing’ individuals. Data were analysed using several mark–recapture estimators, and the derived population estimates ranged from 89 (±5.3, s.e.) horses to 94.7 (±7.9, s.e.) horses. We found that the method gave a level of precision relevant to management, but needs refinement. The technique and its assumptions should be tested further by increasing the number of samples and video should be used to improve identification of individuals. We believe that this is a novel application for aerial surveys, which are typically unsuitable for estimating the size of small populations. This technique was developed for horses but may be used on other conspicuous species with unique natural markings.


Acknowledgements

We thank Parks Victoria for funding the survey, Colleen Nagle and Enzo Brotto from Parks Victoria for participating in the aerial survey and the pilot David Empey for keeping us safe. We also thank James Dawson for reviewing a draft of this manuscript, and three anonymous referees who provided valuable input to the final draft.


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* MJD previously published as M. J. Walter.