Imagine a young woman walking into a bar looking for a date. Now imagine the men in the bar attempting to impress her, either by buying her drinks, dancing, or otherwise showing off. At the end of the night, one of these lucky men will be successful and leave with our imaginary woman. This is roughly* the human equivalent of a lek.
What is a lek?
“Lek” is a rather all-encompassing term that can refer to a mating system, an arena for mating, or a verb to describe the relevant behaviors of those participating in the mating system. Males in species that have lek-mating as a breeding system typically gather in an arena (lek) and produce some sort of display (lekking behavior). Females then come to these leks, browse among the males, and choose a partner to mate with. Afterwards, the female heads off to have her offspring and raise them alone, with no parental care from the male. This allows females to be extremely picky, and leads to highly skewed mating success (with few males getting most of the copulations and most males getting none).
The general idea is that, if you choose an attractive mate, your sons will gain the genetic advantage of being attractive. Having a “sexy son” increases your fitness, because he will be successful in courting the next generation of ladies. It is then the male’s duty to make himself seen by females, and they do so by aggregating together on a lek.
As to how these leks formed, evolutionarily, there are a few well-known hypotheses. The most straightforward of these is the idea that leks provide a space where animals can aggregate to decrease their predation risk. One of the most prominent models of lek formation is the Hotspot Model. Proposed by Bradbury & Gibson, this model suggests that leks form because males aggregate in areas where their chance of encountering females is high. Alternatively is the Hotshot Model, developed by Arak, Beehler, and Foster, which suggests that “unattractive” males should simply clump around attractive males in order to parasitize on his mating success.
I see a problem…
Anyone who has taken genetics might see a potential problem with this mating system. Females are persistently selecting mates based on certain male traits, which should decrease the variation in these male traits via sexual selection, and thus reduce the benefits of choice. This is called the lek paradox.
Some attempted resolutions to the lek paradox include the ideas that: a) the favored trait is multigenetic, b) the favored trait is condition-dependent, or c) different females favor different traits. All of these ideas suggest ways to maintain genetic variance in males despite strong female choice. (To learn more about resolving the lek paradox check out this and this).
So, what animals actually use leks?
Leks were first described in birds, but species ranging from insects to ungulates use lek mating systems. Lekking birds are still the most well-known of the lek-mating animals, particularly the various grouse species in North America, as well as manakins and birds-of-paradise from Central/South America and New Guinea, respectively. Other lekking species include: the Ungandan kob (an antelope relative), fruit bats, some fish, as well as some insects, moths, and butterflies. I’ve included a video above and a photogallery below to demonstrate the amazing diversity of lekking species. You’ll notice that most of these species have elaborate ornamentation used to attract and display to females.
Arak, A. (1982). Sneaky Breeders. Producers and Scroungers: Strategies of Exploitation and Parasitism. C. J. Barnard. Beckenham, U.K., Croom Helm: 154-194.
Beehler, B. M. and M. S. Foster (1988). “Hotshots, hotspots, and female preference in the organization of lek mating systems.” American Naturalist: 203-219.
Bradbury, J. W. and R. M. Gibson (1983). “Leks and mate choice.” Mate choice. Cambridge University Press, Cambridge: 109-138.
Höglund, J. and R. V. Alatalo (2014). Leks, Princeton University Press.
Pomiankowski, A. and A. Moller (1995). “A resolution of the lek paradox.” Proceedings of the Royal Society of London B: Biological Sciences 260(1357): 21-29.
Tomkins, J. L., J. Radwan, J. S. Kotiaho and T. Tregenza (2004). “Genic capture and resolving the lek paradox.” Trends in Ecology & Evolution 19(6): 323-328.