The ability to recognize individuals is an important aspect of social interactions, but it can also be useful to
avoid repeated matings with the same individual. The Coolidge effect is the progressive decline in a male’s
propensity to mate with the same female combined with a heightened sexual interest in new females.
Although males that recognize previous par tners and show a preference for novel females should have a
selective advantage as they can distribute sperm evenly among the females they encounter, there are few
invertebrate examples of the Coolidge effect. Here we present evidence for this effect in the burying beetle
Nicrophor us vespilloides and examine the mechanism underlying the discrimination between familiar and
novel mates. Burying beetles feed and reproduce on vertebrate carcasses, where they regularly encounter
conspeciﬁcs. Males showed greater sexual interest in novel females (virgin or mated) than in females they
had inseminated before. The application of identical cuticular extracts allowed us to experimentally create
females with similar odours, and male responses to such females demonstrated that they use female
cuticular patterns for discrimination. The chemical analysis of the cuticular proﬁle revealed greater inter-
individual variation in female than in male cuticular patterns, which might be due to greater selection on
females to signal their individual identity.