Egg size, begging behaviour and offspring fitness in Nicrophorus vespilloides

Egg size reflects the amount of energy that female parents have invested in their offspring prior to hatching, and is thus often used as a proxy for prehatching investment. According to life history theory, prehatching investment, in turn, trades off with posthatching investment, as the amount of resources allocated at the prehatching stage diminishes the resources available at the posthatching stage. As small eggs have smaller energy reserves than large eggs, the offspring originating from small eggs may have higher hunger levels, and thus beg more, offering the parents information about the need for more posthatching care. However, little is known about the relationship between egg size and begging behaviour, and the fitness correlates of the two. In this study, we directly investigated the association between these two traits in the burying beetle Nicrophorus vespilloides. Concurrently, we examined the effects of egg size on two components of offspring fitness: offspring growth and survival. We found no association between egg size and offspring begging behaviour. Egg size did, however, show a mostly positive, albeit indirect, association with offspring fitness traits (development time, size and survival). Therefore, an increase in egg size does have an impact on offspring fitness, but this impact is not mediated through offspring begging. To our knowledge, this is the first time the relationship between egg size and begging behaviour has been investigated directly.