Abstracts (first author)
The costs of helping behaviour in cooperatively breeding warblers
In several animal species, subordinate individuals forego independent breeding to assist others in raising offspring that are not their own. Several benefits underlying the evolutionary stability of such seemingly altruistic helping behaviour have been invoked, and assessment of variation in individual investment in response to variation in such benefits is often being used to reveal the adaptive significance of these benefits. In the Seychelles warbler Acrocephalus sechellensis, subordinates gain substantial fitness benefits of helping: individuals that start as helpers have higher life time fitness than subordinates that do not help initially. Nonetheless only about half of the subordinates do help. Using a range of physiological measures, we show here that helping carries a substantial cost, as helpers were in poorer condition after the breeding season than non-helping subordinates . Additionally, only individuals in good condition do provide help, because probably only these individuals can overcome the associated costs. This result suggests that, apart from the associated benefits, variation in subordinates’ condition explains part of the variation in helping behaviour. This highlights that considering the condition of the (potential) helper and the costs of helping are important to unravel the benefits of helping, and to understand the variation in the expression of helping behaviour within species.