Conflict or consensus? Synchronous change in mother–young vocal communication across weaning in the cat

Since parent–offspring conflict theory was first proposed, a number of studies in a range of mammalian species have questioned its importance, suggesting that coordination, rather than conflict, occurs during weaning. In this study we propose a set of behaviours for studying the development of the mother–offspring relationship: offspring separation calls and the corresponding maternal response, which can be used to describe the continually developing motivational changes in both parties accompanying weaning. We recorded and analysed separation calls of kittens of the domestic cat, Felis silvestris catus, during the first two postnatal months, and performed playback experiments to observe their mothers' behavioural response. Three different stimuli were played back: calls of the mothers' kittens at their correct age, calls of their kittens from an earlier age (1 week old) and a control sound. We found that kittens' separation calls changed in several respects across the 8 weeks of the study. After the first postnatal month, the number, intensity and fundamental frequency of calls declined markedly, while kittens' latency to call increased. In parallel, we found that during playback tests, mothers' willingness to return to the nest or reunite with their kittens decreased notably as the kittens approached weaning age. Since this decline was present even when mothers were played back the calls of their own kittens previously recorded at an earlier age, we conclude that the decline in responsiveness was not due to a change in the kittens' vocalizations, but rather to a change in the mothers' motivational state. Our findings support the view that weaning in the domestic cat is a well-synchronized process between mothers and offspring, at least under the favourable nutritional conditions of the present study.