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Are behavioural trade-offs all they seem? Counter-intuitive resolution of the conflict between two behaviours

Morrell, Lesley J.



The understanding of trade-offs between behaviours is fundamental to the study of animal behaviour. Individuals may often be faced with the choice of which of two mutually incompatible behaviours to perform. Here, I present a model investigating the trade-off between two behaviours, where one of the behaviours is crucial to the success of the other. I illustrate the results with examples, considering particularly a trade-off between territorial defence and courtship. I investigate how the ability of an individual to perform the behaviours changes the time or energy allocated to each behaviour. Intuition suggests that the time invested in performing a behaviour should decline as the individual's ability to perform the behaviour increases. Explicit, quantitative modelling suggests that this is not always the case. Instead, we see a pattern where investment in one of the behaviours at first increases and then decreases as the ability to perform the behaviour increases. This finding has implications for the empirical study of trade-offs between behaviours, since it could appear that individual ability has no effect on the trade-off under consideration. I discuss potential methods for distinguishing whether time allocation changes in a counter-intuitive, non-monotonic way with increasing individual ability, or whether there is indeed no effect.


Morrell, L. J. (2004). Are behavioural trade-offs all they seem? Counter-intuitive resolution of the conflict between two behaviours. Behavioral Ecology and Sociobiology, 56(6), 539-545.

Journal Article Type Article
Acceptance Date Oct 31, 2004
Online Publication Date Jul 16, 2004
Publication Date 2004-10
Print ISSN 0340-5443
Electronic ISSN 1432-0762
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 56
Issue 6
Pages 539-545
Keywords courtship; defence; individual ability; time budgets; trade-off;
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