Abstract
If generalist predators are to hunt efficiently, they must track the changing costs and benefits of multiple prey types. Decisions to switch from hunting preferred prey to alternate prey have been assumed to be driven by decreasing availability of preferred prey, with less regard for accessibility of alternate prey. Olfactory cues from prey provide information about prey availability and its location, and are exploited by many predators to reduce search costs. We show that stoats Mustela erminea, an alien olfactory predator in New Zealand, are sensitive to the search costs of hunting both their preferred rodent prey (mice) and a less desirable alternate prey (locust). We manipulated search costs for stoats using a novel form of olfactory camouflage of both prey, and found that stoats altered their foraging strategy depending on whether mice were camouflaged or conspicuous, but only when locusts were also camouflaged. Stoats gave up foraging four times more often when both prey were camouflaged, compared to when mice were conspicuous and locusts camouflaged. There were no differences in the foraging strategies used to hunt camouflaged or conspicuous mice when locusts were easy to find. Consequently, camouflaged mice survived longer than conspicuous mice when locusts were hard to find, but not when locusts were easy to find. Our results demonstrate that predators can integrate search costs from multiple prey types when making foraging decisions. Manipulating olfactory search costs to alter foraging strategies offers new methods for understanding the factors that foreshadow prey switching.
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Acknowledgments
We thank R. Pech and A. Byrom for facilitating our visit to Landcare Research and helpful discussions, G. Morriss for technical assistance with video equipment, J. Arrow and all the staff of the Lincoln Animal Research Facility for their generous assistance during the experiment, and J. Dunkerley for help during fieldwork. This study was funded by the ARC Discovery Grant DP0881455 awarded to P.B.B. and conducted in accordance with UNSW Animal Ethics Approval 09/92A. It is dedicated to the late DC Price.
Author contribution statement
C.J.P. and P.B.B. conceived and designed the experiments. C.J.P. performed the experiments and analysed the data. C.J.P. and P.B.B. wrote the manuscript.
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Communicated by Janne Sundell.
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Price, C.J., Banks, P.B. Increased olfactory search costs change foraging behaviour in an alien mustelid: a precursor to prey switching?. Oecologia 182, 119–128 (2016). https://doi.org/10.1007/s00442-016-3660-z
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DOI: https://doi.org/10.1007/s00442-016-3660-z