NEST INTRUSIONS, INFANTICIDE, AND PARENTAL CARE IN THE BURYING BEETLE, NICROPHORUS-ORBICOLLIS (COLEOPTERA, SILPHIDAE)

Duration of paternal care in the burying beetle Nicrophorus orhicollis Say is highly variable. Both parents bury and defend mouse-sized vertebrate carcasses as food resources for their offspring, but males abandon their broods several days before females. Nests defended by single female parents were taken over by aggressive conspecifics in five of nine cases, whereas only six of 16 nests defended by both parents were taken over. In the event of a takeover, the intruding beetle replaced the resident beetle of the same sex, destroyed any eggs that were present, and paired with the remaining resident to produce a new clutch. Broods raised by usurpers following takeovers were less successful than broods raised by initial residents on unused carcasses. The majority of takeovers occurred 3-5 days after carcass burial. The occurrence of nest intrusions by conspecifics did not significantly influence duration of male parental care; when conspecific intruders were excluded from nests males remained with their broods (+/- S.E.) 11.2 +/- 0.8 days (n = 15), and when intruders were added to nests males remained with their broods 12-2 +/- 0.6 days (n = 8). Conflict for carcasses intensified in response to larger brood mass, but duration of male care was unaffected by brood mass. Overall, brood mass and the presence or absence of intruders explained only 5% of the variance associated with brood abandonment by males.