Additional Information on the Relationship between Intra-specific Aggression and Anti-predator Behaviour in the Three-spined Stickleback, Gasterosteus aculeatus


Department of Zoology, University of Glasgow, Glasgow, G12 8QQ, U.K.


18 non-breeding three-spined sticklebacks from a heavily predated site a further 24 fish from a predator-free site were screened for their responses to a realistic model pike. The behaviour of the same fish when confronted with a territorial intruder during the breeding season was also recorded, the two tests being carried out in random sequence and with an interval of at least 6 weeks. Multivariate analyses identified major behavioural dimensions in the pike test and in the intruder test, summarized by the labels ‘boldness’ and ‘aggression’ respectively. Sticklebacks from the heavily predated site were both less bold and less aggressive than those from the unpredated site. Levels of aggression for individuals within each population were positively correlated with their boldness scores, but only for the period when the subjects were recovering from a simulated predatory attack.