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Ecology, management and conservation in natural and modified habitats
RESEARCH ARTICLE

Frequency and precision of aerial surveys for kangaroo management

A. R. Pople
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The Ecology Centre, School of Integrative Biology, University of Queensland, Brisbane, Qld 4072, Australia. Present address: Invasive Plants and Animals, Biosecurity Queensland, Department of Primary Industries and Fisheries, GPO Box 46, Brisbane, Qld 4001, Australia. Email: tony.pople@dpi.qld.gov.au

Wildlife Research 35(4) 340-348 https://doi.org/10.1071/WR07066
Submitted: 8 June 2007  Accepted: 24 December 2007   Published: 27 June 2008

Abstract

The appropriate frequency and precision for surveys of wildlife populations represent a trade-off between survey cost and the risk of making suboptimal management decisions because of poor survey data. The commercial harvest of kangaroos is primarily regulated through annual quotas set as proportions of absolute estimates of population size. Stochastic models were used to explore the effects of varying precision, survey frequency and harvest rate on the risk of quasiextinction for an arid-zone and a more mesic-zone kangaroo population. Quasiextinction probability increases in a sigmoidal fashion as survey frequency is reduced. The risk is greater in more arid regions and is highly sensitive to harvest rate. An appropriate management regime involves regular surveys in the major harvest areas where harvest rate can be set close to the maximum sustained yield. Outside these areas, survey frequency can be reduced in relatively mesic areas and reduced in arid regions when combined with lowered harvest rates. Relative to other factors, quasiextinction risk is only affected by survey precision (standard error/mean × 100) when it is >50%, partly reflecting the safety of the strategy of harvesting a proportion of a population estimate.


Acknowledgements

This project was supported by an ARC SPIRT grant to Hugh Possingham, Gordon Grigg and Stuart Phinn at the University of Queensland, with financial contributions from Queensland, New South Wales, South Australian and Commonwealth conservation agencies and Packer Tanning. The manuscript was improved by comments from two anonymous referees.


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