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Simon Verhulst


Sexual conflict occurs when the optimal solution regarding e.g. a life history trait differs between co-operating individuals of different sex. When deciding a conflict is not instantaneous, some form of negotiation can be expected to evolve. In great tits, Parus major, a sexual conflict exists over the number of clutches that are reared, because the fitness costs of a second clutch are greater for females. A conflict is also likely to exist over investment in the first brood - each parent benefiting from a greater investment by the partner. Male great tits sing when rearing the first brood, and if acoustic signals play a role in the negotiation of a sexual conflict, a positive association between male song rate and maternal investment is predicted. In agreement with this hypothesis, maternal effort (in kJ/day) relative to paternal effort was positively correlated with male song rate. Furthermore, females were more likely to start a second clutch when their male had a high song rate, and high song rate was associated with shorter inter-clutch intervals. Song rate was higher when brood size was experimentally reduced and, independent of brood size manipulation, males with high song rate produced higher quality fledglings. These results indicate that song rate reflects the males' state, suggesting it may function as a handicap signal. Although song rate seems too low (<4% of time) for honesty to be maintained by production costs alone, signalling costs may be amplified by the fact that song appears restricted to the time when the male and female are both near the nest. To achieve a high song rate, the male may have to spend a large amount of time near the nest, thereby seriously restricting time available for other activities.

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Evolution, Function, Development and Causation

Tinbergen's Four Questions and Contemporary Behavioural Biology

Edited by Johan Bolhuis and Simon Verhulst

Ethologist and Nobel laureate Niko Tinbergen laid the foundations for the scientific study of animal behaviour when he formulated its four main problems: evolution, function, development and causation. Celebrating the fortieth anniversary of the publication of Tinbergen’s classic article ‘On aims and methods of ethology’, in this book an international cast of leading behavioural biologists reflect on the enduring significance of his groundbreaking proposals. Following a reprint of Tinbergen’s seminal paper on the famous ‘four why’s’, a contemporary perspective is presented on each of the four problems. In addition, two essays discuss the wider significance of recent trends in evolutionary psychology and neuroecology to integrate the four why’s. This wide ranging book, with a foreword by Aubrey Manning, will appeal to students and researchers in behavioural biology, experimental psychology and cognitive neuroscience.