Burying beetles: intraspecific interactions and reproductive success in the field

ABSTRACT. 1. The discovery and utilization of small carcasses by burying beetles (Silphidae, Nicrophorus) was studied by placing dead mice at random points on large grids at two Iocations in Michigan, U.S.A. 2. The majority of mice are found within 24 h by more beetles than ulti-mately will utilize the carcass. If a carcass is likely to be usurped by a larger species of beetle or by a vertebrate, then intraspecific competition may be post-poned until the carcass is concealed and buried. 3. Both males and females practice parental care. Maturing broods are tended by no adults, a single female, a singIe male, or a male-female pair. No differences in brood success were observed among these categories. 4. The female lays a larger clutch than ultimately will survive. Brood size is regulated after the egg stage, such that offspring number varies, but individual offspring size does not. 5. A large amount of unexplained variation exists in brood size, in both the laboratory and the field. This variation is probably caused by the environment, and not the reproductive physiology of the beetles. Competition with microbes is a likely candidate. 6. Differences exist not only between Nicrophorus species, but also between localities for a single species, suggesting adaptation to local environments. Key words. Silphidae, Nicrophorus, burying beetles, cooperation, parental care, reproductive success