No evidence for parent-offspring competition in the burying beetle Nicrophorus vespilloides

In species where family members share a limited pool of resources, there may be competition between parents and their dependent offspring for access to these resources. Parent-offspring competition may impose a cost to family living that would constrain the evolution of parental care and family living. Yet, few studies have tested for evidence of parent-offspring competition. Here we test for parent-offspring competition in the burying beetle Nicrophorus vespilloides. This species breeds on carcasses of small vertebrates that serve as food for both parents and offspring. We used a two-by-two factorial design, where we manipulated female nutritional state (food deprivation vs. control treatments) and the amount of resources (small vs. large mouse carcasses). We find that food-deprived females lost more mass than controls over the 9-day long food deprivation treatment, confirming that food deprivation caused a substantial decline in female nutritional state at the start of breeding. However, we find no evidence that increased food consumption by food-deprived females had a greater impact on offspring growth or survival when breeding on small carcasses. Instead, poor female nutritional state had a negative impact on offspring survival when females bred on large carcasses. There was more mould on the carcass when food-deprived females bred on a large carcass, suggesting that such females provided less indirect care serving to suppress microbial growth. We conclude that parent-offspring competition is associated with relatively minor costs to family members in this species, suggesting that it may not necessarily constrain the evolution of parental care and family living.