Time constraints and trade-offs among parental care behaviours: effects of brood size, sex and loss of mate

Animals that provide care to their offspring are likely to face time constraints and, consequently, need to trade-off allocations of time among different behavioural activities. Parental allocation of time is often influenced by intrafamilial conflicts including conflicts of interests between parent and offspring and between parents over optimal parental effort. We investigated effects of offspring demand (by manipulating brood size) and loss of mate (by experimental removal of mate) on allocation of time among parental and nonparental behaviours in the burying beetle Nicrophorus orbicollis. With increasing offspring demand, allocation of time to parental care occurred at the cost of nonparental behaviours. Time allocation among parental care behaviours changed with offspring demand. Time spent on care behaviours from which offspring benefit simultaneously did not change with increasing offspring demand. In contrast, time spent on care behaviours that offspring receive individually increased with increasing brood size. This suggests that costs for parents and benefits for offspring differ considerably among parental care behaviours. Removal of the mate affected males and females differently. Widowed males increased their effort, whereas widowed females showed no change in their effort. This result suggests that males and females negotiate their parental effort differently, and costs and benefits of parental care differ considerably between the sexes. In general, our study shows a plastic parental response to mate loss and simultaneous change in offspring demand, indicating that parents negotiate parental efforts while considering offspring demands. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.