Mate choice in lekking sage grouse revisited: the roles of vocal display, female site fidelity, and copying

In lekking sage grouse (Centrocercus urophasianus), females exhibit relatively unanimous mate choice for particular males, but a satisfactory explanation for this unanimity has been elusive. We present analyses of mating distributions from two leks over 4 years that provide evidence for female choice based on differences in vocal display performance of males, the locations at which hens mated in the previous year, and the choices of other females (copying). The unanimity of female choice varied markedly among leks and years in correlation with changes in the mean numbers of hens that mated at the same time and hence the opportunity to copy. The results confirm that hens assess phenotypic traits of males directly but also indicate that the secondary tactics of site fidelity and copying are often important components of female choice. The occurrence of these secondary tactics has three implications: the variance in mating success among lek males will be a poor predictor of the intensity of sexual selection on specific traits; female preferences may generate more clustered dispersions of displaying males than predicted by hotspot settlement models; and direct assessment of males by females may be difficult or costly, a conclusion that supports adaptive models of sexual selection over a nonadaptive Fisherian process. [Behav Ecol 1991;2:165-180]