Behavioral Syndromes in Stable Social Groups: An Artifact of External Constraints?

Abstract

Individuals of many species differ consistently in their behavioral reactions toward different stimuli, such as predators, rivals, and potential mates. These typical reactions, described as ‘behavioral syndromes’ or ‘personalities,’ appear to be heritable and therefore subject to selection. We studied behavioral syndromes in 36 male fowl living in 12 social groups and found that individuals behaved consistently over time. Furthermore, responses to different contexts (anti-predator, foraging, and territorial) were inter-correlated, suggesting that males exhibited comparable behavioral traits in these functionally distinct situations. We subsequently isolated the same roosters and conducted tests in a ‘virtual environment,’ using high-resolution digital video sequences to simulate the anti-predator, foraging, and territorial contexts that they had experienced outdoors. Under these controlled conditions, repeatability persisted but individual responses to the three classes of stimuli failed to predict one another. These were instead context-specific. In particular, production of each type of vocal signal was independent, implying that calls in the repertoire are controlled by distinct mechanisms. Our results show that extrinsic factors, such as social position, can be responsible for the appearance of traits that could readily be mistaken for the product of endogenous characters.