Timing of oviposition enables dominant female burying beetles to destroy brood-parasitic young

Infanticide can increase an individual’s reproductive success through reduced competition for its offspring. Here we document the occurrence and effects of infanticidal behaviour by dominant female burying beetles, Nicrophorus vespilloides, in nontolerant breeding associations. Burying beetles feed and guard their young on buried carcasses, and on small carcasses, conspecific females engage in intense aggression. Dominants largely exclude subordinates from the carcass and are the sole caregivers for the larvae. Although subordinates and dominants produce similar egg clutches, only one out of five surviving offspring is the subordinate’s. We hypothesized that much of this skew is due to temporally cued infanticide by dominants. Females oviposit over the course of 24–48 h, and kill larvae they encounter prior to the hatching of their own larvae. Such infanticide can lead to significant skew only if the dominant’s larvae hatch significantly later than the subordinate’s, and if more subordinate than dominant larvae hatch during the infanticidal phase. The subordinate’s share of larvae hatching during the parental phase must be smaller than her share of eggs, and the portion of subordinate larvae killed by the dominant should increase with an increasing difference in oviposition time between the two females. These predictions were met. Dominant females, who had exclusive access to the carcass and larvae, were able to use temporal cues to destroy over half of the subordinates’ first-instar larvae. This is the first study to unambiguously document the primary mechanism underlying reproductive dominance in nontolerant associations of female N. vespilloides.