Signalling of hunger by senior and junior larvae in asynchronous broods of a burying beetle

Offspring of many animal species signal their nutritional needs to the parents by conspicuous vocal, visual or tactile begging displays. Studies on asynchronously hatching altricial birds show that junior (i.e. late-hatched) offspring beg more than senior (i.e. early-hatched) offspring for a given level of food deprivation, but that juniors and seniors otherwise respond similarly to changes in their hunger levels. Asynchronous hatching and begging are not unique to altricial birds but occur in some nonavian species, such as the burying beetle Nicrophorus vespilloides. We investigated the effects of asynchronous hatching on offspring begging behaviour in N. vespilloides. Food-deprived larvae spent more time begging than fed larvae and junior larvae spent more time begging than senior larvae. However, we found no evidence that seniors and juniors responded differentially to food deprivation. We conclude that asynchronous hatching has a remarkably similar effect on offspring begging in altricial birds and burying beetles. Furthermore, we suggest that the effects of asynchronous hatching on the evolution of offspring begging tactics are independent of whether the offspring obtain all their food by begging from the parents, as is the case in altricial birds, or whether the offspring obtain some food by begging from the parents and some by self-feeding independently of the parents, as is the case in burying beetles.