Carcass Age and Reproductive Costs for Nicrophorus orbicollis (Coleoptera: Silphidae)

The life history costs of living in microbially dense environments can be high. To assess the importance of these costs for natural selection, it is necessary to know how costs vary with environmental conditions. Adult burying beetles prepare vertebrate carcasses of varying age and states of deterioration as a resource for their young. In the present study, Nicrophorus orbicollis Say females were presented with either fresh or aged (80 h) large carcasses (30-39 g) to examine effects on their lifetime reproductive success (four reproductive attempts) and survival. Reproductive success and survival were also measured for female offspring that developed on fresh and aged carcasses. Carcass age had no measurable effect on lifetime reproductive output or life span of either parents or their adult offspring. In a separate experiment using medium-sized carcasses (22-24 g), the reproductive performance of females in a single reproductive attempt was negatively affected by carcass age (13.9% less brood mass). The results suggest that the costs of using a single older carcass are relatively minor when measured over a lifetime. Alternative costs of using older carcasses and explanations for the complex antimicrobial traits of burying beetles are discussed.