Risk-taking in stickleback fishes faced with different predatory threats

Abstract

:An animal’s behavioural response to predators should depend in part on its vulnerability to predation, which may be mediated by morphological antipredator defences. In this study we compared the behaviour of two sympatric species of stickleback (Pisces: Gasterosteidae), each characterized by a different amount of defensive armour, in response to simulated fish and bird predatory threats under controlled laboratory conditions. We tested the general hypothesis that the more robustly armoured, and presumably less vulnerable, threespine stickleback (Gasterosteus aculeatus) would exhibit less pronounced antipredator behaviour and be bolder when threatened with either a predatory fish or bird model than the poorly armoured ninespine stickleback (Pungitius pungitius). As expected, threespine sticklebacks behaved more boldly in the face of fish (charr) predation hazard (i.e., shoaled less, and approached the predator more frequently, more closely and for longer periods) than ninespine sticklebacks. In comparison, however, the two species did not differ significantly in their response to a simulated heron attack. These findings suggest that an individual’s behavioural response to a threat of predation is mediated by the amount of defensive armour it possesses and the effectiveness of this armour against different types of predator.