Nestmate recognition in burying beetles: the "breeder's badge" as a cue used by females to distinguish their mates from male intruders

Burying beetles use small vertebrate carcasses as food for their larvae and defend these carcasses against intra- and interspecific competitors. Breeding associations on carcasses can consist of single females, heterosexual pairs, or various combinations of males and females. When a heterosexual pair collaborate in a breeding attempt, they do not typically exhibit aggressive behavior toward each other, but do attack newly arrived conspecifics that attempt to usurp the carcass. We investigated the cues involved in discrimination between breeding partners and intruders by female burying beetles. We found that resident females tolerate males that have cared for a brood, as well as males that have not cared for a brood but have been on a carcass for a day or two. Males that have had no prior contact with a carcass are attacked. Females appear to use a chemical cue, the "breeder's badge," an apolar substance on the male's cuticle that can be removed by washing with pentane. This cue is reliably correlated with recent male experience with a carcass that is suitable for reproduction. The breeder's badge develops as a result of prolonged contact with such a carcass, and disappears on removal from the carcass; its presence does not require contact with a female or with larvae. Female recognition of their male partners in burying beetles thus does not involve individual recognition, but rather recognition of reproductive condition.