Development of behavioural differences between individuals and populations of sticklebacks, Gasterosteus aculeatus

Behavioural syndromes are correlations between behaviours in different contexts. For example, an individualʹs behaviour in response to a predator might be related to the same individualʹs behaviour towards conspecifics. We examined the developmental stability of single behaviours (activity in an unfamiliar environment, aggressive behaviour and boldness under predation risk) and correlations between these behaviours in two Californian populations of three-spined sticklebacks. Individually marked fish were measured for all three behaviours at three points during development, as juveniles, subadults and adults. Even though single behaviours were unstable through time, some correlations between behaviours were stable. For example, in one population, neither boldness nor aggression was stable but the positive correlation between them was. Certain correlations between behaviours were apparent at some developmental stages but not others, and the pattern of correlations differed between the two populations. These data suggest that behavioural syndromes do not necessarily limit behavioural plasticity, and suggest that ecological and developmental circumstances might favour different suites of traits.