Sex and age influence responses to changes in the cost of cooperative care in a social carnivore

Abstract

In cooperative breeders, variation in contributions to offspring care will often be determined by variation in the cost of care. Because the cost of investment is determined by its effect on residual reproductive value, a unit of care should impose different fitness costs on different life-history categories of helper. This means that a change in current condition should have category-specific effects on contributions to care. I test this in the cooperatively breeding banded mongoose (Mungos mungo), experimentally increasing the cost of care by subjecting helpers to temporary deprivation. I observed category-specific effects on pup provisioning: For a given percentage weight loss, female helpers reduce their provisioning by a greater extent than male helpers. This is likely to be because variation in condition has a stronger effect on female reproductive success, so females should be under stronger selection to limit the cost of offspring care. I also observed an unexpected effect of age, with older helpers reducing their provisioning by more than younger helpers. This is probably because older helpers are more likely to breed themselves, so changes in condition may have a more immediate effect on direct fitness. In general, category-specific responses to changes in state should occur wherever there are existing category-specific differences in contributions to care, in both cooperative breeders and biparental species. © 2010 The Author.