Courtship reduces longevity of male Drosophila melanogaster

Male Drosophila melanogaster exposed to virgin females that were experimentally prevented from mating had a higher death rate than males exposed to an equal number of inseminated females. Exposure to virgin females increases the rates of courtship, mating and production of sperm and accessory fluid. The present study attempted to disentangle the relative contributions of these reproductive activities to the elevated male death rate. Males in different experimental groups were induced to perform only parts of sexual activity. Comparison of longevities between these groups showed that courtship alone was sufficient to reduce male life span. Mating itself and production of seminal fluid and sperm, on the other hand, did not seem to be costly but, since any mating costs were confounded with costs of courtship, definite conclusions cannot be drawn. Surprisingly, wild type males kept with females that could not copulate died sooner than males kept with females that could mate. Despite several behavioural differences between these experimental groups, only mounting attempts showed a pattern consistent with that of longevities. Mounting attempts may be an indicator of an altered metabolic rate or hormonal status that renders the males more susceptible to death. (C) 1996 The Association for the Study of Animal Behaviour