The lek mating system is a unique and intense form of communal breeding where males gather in a specific area solely to display their fitness for potential mates. This aggregation, known as a lek, serves as a marketplace where females visit for the single purpose of selecting a partner for copulation. Lekking is defined by the absence of resource defense; the territory does not contain resources like food, water, or nesting sites attractive to females. The male’s entire contribution to the reproductive process is limited to his genes and the act of mating, with no subsequent parental care provided to the female or the offspring. This focus on display alone makes the lek system a powerful driver of sexual selection, giving rise to some of the most elaborate male ornaments and behaviors in the animal kingdom.
Defining the Communal Display Ground
The term “lek” refers to the physical site where males congregate, while “lekking behavior” describes the competitive displays performed there. These display grounds are often traditional, meaning males return to the same location year after year, and they are typically situated in open areas that offer good visibility for advertising their presence to females. A classic lek is characterized by tightly clustered male territories, where individuals are often within both visual and auditory range of their neighbors, such as with the Greater Sage-Grouse. In contrast, an exploded lek features males that are more widely dispersed, sometimes separated by kilometers, but remain within auditory contact, as seen in the Kākāpō.
The small territories defended by the males contain no resources of value to the female, which separates the lek system from other forms of polygyny. The male defends only a small patch of ground for the purpose of his display and mating. Because males are emancipated from providing resources or parental care, their efforts are entirely redirected toward attracting a mate through elaborate courtship and intense competition. This arrangement focuses the female’s choice exclusively on the male’s physical traits and display quality.
The Dynamics of Male Competition
The lek functions as an arena of hyper-intense competition among males to secure mating opportunities. Males engage in ritualized aggressive encounters, which can involve sparring, chasing, vocalizations, or complex visual signaling to establish a dominance hierarchy. The competition is so fierce that it results in an extremely skewed mating success rate, where a small minority of males are responsible for nearly all successful copulations.
The most successful males often occupy the “hotspot” or center of the lek, which is the area most preferred by visiting females. In many well-studied lek systems, the top-ranking males in the central territories may account for 80% to 90% of all matings. This concentration of success suggests that the spatial arrangement is not random, but is driven by a female bias for central males, which intensifies competition for those positions. Subordinate males benefit by clustering around these dominant individuals, possibly to intercept females or to inherit the prime display site later, a concept known as the “hotshot” hypothesis.
Why Females Prefer a Collective Mate Market
Females visit leks for a rapid and efficient assessment of potential partners, as the collective gathering of males offers a comparative shopping experience. This collective mate market allows a female to observe and compare the displays of many males in one location before committing to a choice. One major hypothesis explaining this behavior is the “Good Genes” theory, which posits that females select males based on traits that signal superior genetic quality, such as bright coloration, elaborate dances, or vigorous health. By selecting the most impressive male, the female gains indirect benefits by ensuring her offspring inherit these beneficial genes, leading to increased viability and fitness.
The “Safety in Numbers” hypothesis suggests that aggregating reduces the individual risk of predation during the vulnerable period of mate selection. While the act of visiting a lek does increase a female’s exposure to predators like eagles, the risk per individual can be lowered by being part of a larger group. The cost of this careful choice is minimal compared to the potential long-term genetic benefit for her offspring.
Lekking Across Different Species
Lekking has evolved independently across a diverse array of animal taxa, demonstrating its effectiveness as a mating strategy. The system is most famously documented in birds, particularly the grouse family, such as the Greater Sage-Grouse and Black Grouse, which perform elaborate dances and vocal displays. The Manakin birds of Central and South America also exhibit lekking, with some species performing complex, coordinated “moonwalks” and wing-snapping sounds to attract females.
Lekking is not exclusive to the avian world, as it is also found in mammals, fish, and insects. Among mammals, certain ungulates like the Topi antelope and the Uganda Kob form leks where males fiercely defend very small patches of territory. Furthermore, some insects, including certain fruit flies and moths, aggregate on specific sunlit leaves or landmarks for competitive display. This wide taxonomic distribution underscores the power of sexual selection when males provide no resources and females are free to choose purely on the basis of displayed quality.