In order to investigate any size-dependent differences between behavioural patterns, wild-caught Hart's rivulus Rivulus hartii of varying sizes were exposed to chemical alarm cues extracted from the skin of conspecifics or heterospecific Poecilia reticulata, or a tank water control, in a series of laboratory trials. In response to conspecific alarm cues, R. hartii subjects of the range of body sizes tested exhibited consistent, size-independent antipredator behaviours that were characterized by decreased locomotory activity and foraging levels and increased refuging behaviour. Conversely, focal R. hartii demonstrated significant size-dependent trends in response to heterospecific alarm cues, with smaller individuals exhibiting antipredator responses and larger individuals shifting their behaviour to increased levels of activity consistent with a foraging, or predatory, response. These results show that the behavioural responses of individual R. hartii to publicly available chemical alarm cues from heterospecifics are mediated by the size of the receiver.

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Keywords Antipredator behaviour, Chemical alarm cues, Guppy, Life history, Predation, Rivulus
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Journal Journal of Fish Biology
Elvidge, C.K., Ramnarine, I.W., Godin, J.-G.J, & Brown, G.E. (2010). Size-mediated response to public cues of predation risk in a tropical stream fish. Journal of Fish Biology, 77(7), 1632–1644. doi:10.1111/j.1095-8649.2010.02798.x