Wiley, R. H.   1991.   Lekking in birds and mammals: behavioral and evolutionary issues.   Advances in the Study of Behavior 20:   201-291.


For species in which females have no associations with males except for brief periods preceding copulation, mating at leks probably enhances a female's discrimination of optimal mates, ones advantageous either for increasing the viability of her offspring or perhaps for reducing the immediate risks of copulation.

The behavioral mechanisms by which this discrimination occurs are not yet well established for any species and might well differ among species or even among populations of the same species.

These mechanisms might involve interactions among females, including learned traditions, as well as interactions among males and between females and males. Sexual selection could result from indirect, as well as direct, consequences of female preferences.

The costs of display and ornamentation for males at leks are indicated by higher mortality of adult than younger males and greater energy expenditure by successful males. Advantages to females of choosing mates at leks remain mostly undocumented.

A general feature of mating at leks is a later onset of successful reproduction by males than by females. Age-related mating success of males on leks continues, at least in some cases, beyond the age at which fully developed morphology is attained and is, again at least in some cases, related to territorial succession or succession in dominance.

Female preferences for mating at particular locations could provide the basis for either of these forms of mating succession and result indirectly in mating with older or more vigorous males.

Strong directional selection as a result of female preferences, either direct or indirect, tends to deplete genetic variation for the preferred male traits. This situation in turn reduces selection for the female preferences based on discriminations among conspecific males, the so-called paradox of the lek.

Transient selection for resistence to parasites could maintain genetic variance for male traits, but evidence necessary to establish this possibility for lekking species is incomplete. The paradox of the lek does not arise when there are fixed costs of indiscriminate mating by females, such as immediate risks during copulation or dysgenic hybridization.

These generalities apply equally well to any species with brief interactions between the sexes and no associations of males with resources used by females. In particular, they apply to species with dispersed, rather than aggregated, display sites.

In some taxa, the evolution of dispersed versus aggregated display appears related to risks of predation in different habitats; in others, this variation has no apparent explanation at present.

All of these species in which copulation occurs at display sites lacking resources, whether aggregated as leks or dispersed, isolate clearly the issues of evolution by sexual selection and thus merit our continuing attention.

[ENTIRE ARTICLE (.pdf file)]