Naïve, bold, or just hungry? An invasive exotic prey species recognises but does not respond to its predators
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Alien species experience both costs and benefits in invaded environments, through naiveté of potential prey species, but also predation pressure from native predators. The question of whether alien prey recognise and respond to native predators has been relatively understudied, despite the hypothesised potential for native predators to provide biotic resistance to invasion. There are two main hypotheses about whether exotic prey should recognise native and exotic predators in their new ranges: (1) naiveté—predicting recognition of evolutionarily familiar predators only, and (2) pre-adaptation—predicting recognition of all predators through a generalist recognition template. With regards to antipredator responses, (3) naïveté theory presumes that exotic prey will respond to the predators they recognise, but we suggest that (4) a bold behavioural syndrome, and/or a high marginal value of food in invaded environments might result in weak or absent responses, even to recognised predators. Here we combine the giving-up density framework with behavioural analysis of remote camera footage to experimentally test these ideas in a disturbed, peri-urban, Australian ecosystem, where alien black rats are predated on by alien dogs, foxes, cats, and native quolls. Black rats recognised dogs and foxes, but appear naïve towards quolls. However, they showed no antipredator responses at all, consistent with a bold behavioural syndrome, elevated predation risk, and/or a high marginal value of food in invaded environments.
KeywordsExotic prey Native predator Olfactory recognition Odour cues Alien Predator–prey interaction
The authors would like to thank Malith Weerakoon, Timothy Ralph, and a long list of volunteers for assistance with odour sample donation, field work, and video scoring. We would also like to thank the editor and one anonymous reviewer for their comments and suggestions, which greatly improved the manuscript.
AJRC and PBB conceived of and designed the study, AJRC completed the fieldwork, analyses, and wrote the first draft of the manuscript. PBB contributed to the data analysis and editing of the manuscript.
AJRC was funded by an Ethel Mary Read Grant from the Royal Zoological Society of New South Wales, and a Joyce W Vickery Fund Research Grant from the Linnean Society of New South Wales. AJRC and PBB were funded by a Hermon Slade Foundation grant, HSF 10/10.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This work was carried out under Australian ethics approval, granted by the University of New South Wales Animal Ethics Committee (approval number 09/99B).
All data will be deposited in Dryad upon acceptance.
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