Paternity, copulation disturbance and female choice in lekking black grouse

Female copulation behaviour in the black grouse, Tetrao tetrix, was studied by detailed observations of individually marked birds together with DNA fingerprinting analyses for paternity assessment. For each breeding occasion females typically mated only once with one male, and did not mate outside the lek arena. They re-mated with the same or another male usually only if the initial copulation was disturbed and was probably unsuccessful in sperm transfer. The willingness of females to copulate only once with one male suggests that multiple mating with several males incurs a cost that more than outweighs any possible fertility or sperm competition benefits. Attempts by neighbouring males to disturb copulations were frequent, but only a small fraction of these were successful in terms of causing the female to re-mate. There was no tendency for females to redirect matings to the males that had disturbed them which also suggests that disturbance risk is not limiting female choice. However, risk of disturbance does increase the cost of female choice, and in that sense it will have some impact on mating decisions, in particular if the benefits of increasing choosiness are not great. (C) 1996 The Association for the Study of Animal Behaviour