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RESEARCH ARTICLE
Contents Vol 37(7)

Prey switching by stoats (Mustela erminea): a supplemental food experiment

Des H. V. Smith A E , Henrik Moller B , Deborah J. Wilson C and Elaine C. Murphy D
+ Author Affiliations
- Author Affiliations

A Centre for Conservation Research, Calgary Zoo, Calgary AB T2E 7V6, Canada.

B Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.

C Landcare Research, Private Bag 1930, Dunedin 9054, New Zealand.

D Research, Development and Improvement Division, Department of Conservation, PO Box 13 049, Christchurch 8141, New Zealand.

E Corresponding author. Email: dess@calgaryzoo.ab.ca

Wildlife Research 37(7) 604-611 https://doi.org/10.1071/WR10088
Submitted: 26 May 2010  Accepted: 19 November 2010   Published: 17 December 2010

Abstract

Context

Prey switching by invasive carnivorans to changing food supply could severely impact on endemic prey of conservation importance, but experimental evidence for prey switching in carnivorans is rare. Stoats (Mustela erminea) were introduced to New Zealand and now threaten survival of many native birds, reptiles and invertebrates.

Aim

Our primary objective was to see whether abundant food caused stoats inhabiting an alpine grassland site to alter the rate at which they preyed upon weta (Orthoptera : Hemiandrus sp.), hares (Lepus europeus), birds and mice (Mus musculus).

Methods

We used dead rabbits as supplemental food in a before-after-control-impact experiment. Stoat scats were collected from a treatment and non-treatment site before and following food supplementation. Percentage frequency occurrence of the different prey types was assessed for the two sites during each experimental phase.

Conclusions

Stoats ate fewer ground weta and hares, the two most abundant prey types, when supplemental food was added. In contrast, consumption of mice remained relatively stable at both sites throughout the experiment, and the consumption of birds declined at both sites.

Implications

Our experiment suggests that stoats may continue to eat scarce endemic prey at similar per capita rates even when alternative prey are available. However, endemic prey that are locally or regionally abundant may be indirectly impacted by fluctuations in alternative prey.


Acknowledgements

We thank Georgina Pickerell, Peter Lei and Nicolas Couedel, who assisted in the field. Gary Tong, manager of the Borland Lodge, helped with accommodation and logistics. C. M. (Kim) King provided valuable comments on an earlier version of this paper. This research was funded by the Department of Conservation’s Stoat Technical Advisory Group (Research Contract: 3652) and the Zoology Department, University of Otago, and was approved by the University of Otago Animal Ethics Committee.


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Appendix 1.  Model estimates of the probability that a prey type would be found in a scat given the site and experimental phase in which the scat was found
For each prey type, estimates are from the interaction model. A dash means an estimate could not be obtained
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