Exploded Lek Mating Systems: When Leks Are Spread Out

An exploded lek is a mating system in which males gather for display and courtship in a defined area, but their territories are spaced much farther apart than in a classic lek, often separated by hundreds of meters instead of meters. Females visit these dispersed male territories specifically to mate, and males provide no parental care beyond sperm. The distinction matters for researchers studying sexual selection, for wildlife managers identifying breeding habitat, and for anyone observing lekking birds or mammals in the field, because the spatial scale changes how you detect the lek, how you count displaying males, and how you interpret female movement patterns.

Defining the Exploded Lek Within Mating System Theory

Mating systems describe how males and females associate for reproduction, and they shape animal distribution, individual reproductive success, and population dynamics. Bats show a greater diversity of mating systems than any other mammalian order, which makes them useful models for understanding the causes and consequences of social organization. Traditional typologies do not accommodate every species, so researchers have proposed a functional framework that classifies mating systems along a male reproductive skew continuum, from monogamy to true lekking. This framework includes seven categories: promiscuity, monogamy, female defence polygyny, resource defence polygyny, a lek-like mating system, exploded classical lek, and clustered classical lek. Applying this framework to bats reveals that lek mating systems are more prevalent in bats than previously recognized.

The exploded lek sits between resource defence polygyny and the clustered classical lek on this continuum. In resource defence polygyny, males defend territories that contain resources females need, such as food or nesting sites. In a clustered classical lek, males display in tight aggregations where females can compare several males within a small area. The exploded lek shares the display aggregation of a classical lek, but the male territories are spread out, so females must travel between males to make comparisons.

Four Criteria for Identifying a Lekking Species

A clear-cut definition of leks is difficult to obtain, so researchers have extended the definition to describe leks as male display aggregations that females attend primarily for the purpose of mating. Four criteria should be verified to identify a lekking species:

1. There is no male parental investment beyond the sperm.
2. Males aggregate at specific sites for display.
3. The only resource females find on the lek is the male, meaning the male genes.
4. Females can select their mates, although the necessity of this condition has been debated.

These criteria were applied to the little bustard, a species claimed to show an exploded lek mating system but never fully investigated. Displaying males showed an aggregated spatial distribution over the study area during two years of survey. Male territories were rather large, averaging 19 hectares with a standard deviation of 16 hectares, and there was large among-male variability in territory size. Land use within the territories included mainly permanent and semi-permanent crops. The variability in land use among territories suggested that resources found within male territories were selected according to male needs for food and display instead of to female needs.

How Exploded Leks Differ From Classic Leks

The primary difference between exploded and classic leks is the distance between displaying males. In a classic lek, such as those of many grouse species, males display within sight and hearing of each other, often within a few meters. In an exploded lek, males are separated by distances that may exceed the range of visual contact, so acoustic signals become more important for attracting females and for mediating male spacing.

The capercaillie grouse provides a useful case study. Research using GPS satellite telemetry examined the spatial relationship of males on exploded leks in this species. The telemetry data allowed researchers to track male movements and positions over time, revealing how males maintained their dispersed territories and how they responded to each other's presence. The spatial relationships among males on exploded leks are not random, but the mechanisms that maintain the spacing differ from those in clustered leks.

Visualizing the Spatial Arrangement

Imagine a classic lek as a small clearing where five to twenty males display within an area the size of a football pitch. A female can stand in the center and see all the males, compare their displays, and choose a mate without traveling far.

Now imagine an exploded lek as a series of display sites spread across a valley or a grassland plain. Each male occupies a territory that may be tens of hectares in size. The males cannot see each other, but they can hear each other's calls. A female must travel from one male territory to the next, assessing each male individually, before she makes her choice. The total area of an exploded lek can be several square kilometers, even though the number of displaying males is similar to that of a classic lek.

This spatial arrangement has consequences for female choice. In a classic lek, females can directly compare males side by side. In an exploded lek, females must remember the qualities of each male they visit, or they may use alternative tactics such as comparing males using relative preference criteria. Traits involved in female choice should be variable between males but not within males, providing reliable cues of male identity and quality for prospecting females.

Species That Use Exploded Lek Mating Systems

Several bird species are known or suspected to use exploded lek mating systems. The little bustard, houbara bustard, capercaillie grouse, and Bulwer's wattled pheasant all provide examples, and some bat species may also use this system.

Little Bustard

The little bustard is an endangered species that shows an exploded lek mating system. Research in western France monitored a population over two years to investigate male aggregation in arenas and the lack of consistent resources in male territories. Displaying males showed an aggregated spatial distribution over the study area, but their territories were large, averaging 19 hectares. The variability in land use among territories suggested that resources were selected according to male needs instead of female needs, which supports the lek interpretation.

Studies of female choice in the little bustard identified male phenotypic traits that showed higher among-male than within-male variation, including plumage pattern, display rates, and call structure. At least four phenotypic male traits correlated with female attraction: body condition, lek attendance, ornamental symmetry, and display rates. Traits related to the initial female attraction to a male territory seemed to differ from traits related to the decision of females to stay in the territory of attractive males.

Houbara Bustard

The houbara bustard in eastern Morocco has been studied for its mating system, and the species is known to use exploded leks. Research on male vocalizations in the houbara bustard investigated whether kinship and inbreeding information is related to low-frequency vocalizations called booms produced by males during courtship. In a captive breeding program where the pedigree of all males was known, researchers found a relationship between the individual inbreeding level of captive males and their vocalization parameters, and kin shared similar frequency and temporal characteristics of their vocalizations. In the wild, there was no evidence for spatial structuring of males based on their acoustic parameters, which agreed with previous genetic findings on the absence of kin association within houbara bustard leks.

Capercaillie Grouse

The capercaillie grouse is a classic example of an exploded lek species. GPS satellite telemetry studies have examined the spatial relationship of males on exploded leks, providing detailed data on how males space themselves across the landscape. The large territories of displaying males mean that the lek extends over a much larger area than a classic lek, and females must travel considerable distances to visit multiple males.

Bulwer's Wattled Pheasant

The Bulwer's wattled pheasant has traditionally been housed in pairs in captivity, although it was unknown whether monogamy is the species' natural mating system. When a group of three males and three females was placed together in a complex outdoor habitat, the data collected indicated that the species may have an exploded lek type of mating system in the wild and that individuals may flock together in the nonbreeding season. Males and females seemed to prefer different types of shade regimes, which suggested ways to improve husbandry and breeding success of the species in captivity.

Wrinkle-Faced Bat

The wrinkle-faced bat is one of the few bat species documented to use lek courtship. Observations in Costa Rica located 53 perches where males hung with raised facial masks at a mean height of 2.35 meters during the first half of the night. Most of the time, the males moved just their wing tips and spontaneously vocalized in the ultrasound range. Approaches of other individuals resulted in the perching male beating its wings and emitting a very loud, low frequency whistling call, and following such an encounter a copulation event was recorded. The observed aggregation of adult males was consistent with lek courtship.

Birds of Paradise

Research comparing nine species of birds of paradise examined display dispersion and diet. The study compared how males of different species spaced their display sites and how their diets related to their mating systems. Some birds of paradise use exploded leks, with males displaying from dispersed sites within a larger area.

Why Some Species Use Exploded Leks

Habitat constraints are a primary reason why some species use exploded leks instead of classic leks. When suitable display sites are patchy or when the habitat does not allow males to gather in tight aggregations, males may spread out while still maintaining the essential features of a lek.

Habitat Structure and Resource Distribution

In the little bustard, male territories included mainly permanent and semi-permanent crops, and the variability in land use among territories suggested that resources were selected according to male needs for food and display instead of to female needs. This finding supports the interpretation that males are not defending resources that females need, which is a key criterion for a lek. The large territory size may reflect the need for males to include enough display sites and feeding areas within their territory while still maintaining spacing from neighboring males.

For the capercaillie grouse, the forest habitat may not allow males to see each other over long distances, so acoustic communication becomes more important. The exploded lek allows males to space themselves according to the acoustic range of their displays, which may be influenced by vegetation density and topography.

Predation Pressure

Predation risk may also influence lek spacing. In a classic lek, the aggregation of males may attract predators, but the large number of eyes can also detect predators earlier. In an exploded lek, males are more dispersed, which may reduce the risk of a predator finding the lek, but each male has less collective vigilance. The tradeoff between predator detection and predator attraction may favor different spacing patterns in different habitats.

Female Movement Patterns

Female movement patterns may also shape lek spacing. If females range over large areas during the breeding season, an exploded lek may be more efficient for them to visit because they can encounter displaying males as they move through their home range. In a classic lek, females must make a special trip to the lek site, which may be costly if the lek is far from their feeding areas.

At a Glance

Practical Assessment Steps for Identifying an Exploded Lek

When you observe a population that may use an exploded lek mating system, follow these steps to confirm the identification. These steps apply to field researchers, wildlife managers, and advanced students conducting behavioral observations.

Step 1: Map Male Display Territories

Record the locations of all displaying males during the breeding season. Use GPS units to mark the center of each male's display activity. Visit the site at different times of day and across the breeding season to ensure you capture the full set of displaying males. For the little bustard, researchers monitored a population over two years to investigate male aggregation in arenas, which shows that multi-year data may be needed to confirm the spatial pattern.

Step 2: Measure Distances Between Males

Calculate the distances between neighboring males using your GPS data. If the distances are consistently large, often hundreds of meters or more, the population may use an exploded lek. Compare your measurements to known examples. Little bustard male territories averaged 19 hectares, which means the distance between territory centers would be several hundred meters.

Step 3: Assess Resources Within Male Territories

Determine whether males are defending resources that females need. Record the vegetation, food availability, and nesting habitat within each male territory. If the resources are selected according to male needs instead of female needs, this supports the lek interpretation. In the little bustard study, land use within territories included mainly permanent and semi-permanent crops, and the variability suggested resources were selected for male needs.

Step 4: Observe Female Behavior

Watch females as they visit male territories. Record how many males each female visits, how long she stays at each territory, and whether she returns to a male after visiting others. In an exploded lek, females must travel between territories to compare males, so you should observe females moving between male display sites.

Step 5: Confirm the Four Criteria

Apply the four criteria for identifying a lekking species. Confirm that males provide no parental investment beyond sperm, that males aggregate at specific sites for display, that the only resource females find on the lek is the male, and that females can select their mates. If all four criteria are met, the species uses a lek mating system, and the spatial scale determines whether it is an exploded or classic lek.

Records and Measurements for Lek Studies

Maintain systematic records when studying exploded leks. The following measurements are essential for comparing populations and for detecting changes over time.

Territory Size and Overlap

Record the size of each male territory and the degree of overlap between neighboring territories. In the little bustard, male territories were rather large with a large among-male variability in territory size. This variability may be important for female choice, as females may prefer males with larger territories or with territories in certain locations.

Display Rates and Timing

Record the frequency and timing of male displays. Display rates were one of the phenotypic traits that correlated with female attraction in the little bustard. Record the time of day when displays occur, the duration of display bouts, and the number of displays per hour.

Female Visitation

Record the number of females that visit each male territory, the duration of each visit, and whether copulation occurs. Female visitation is a direct measure of male attractiveness. In the little bustard, at least four phenotypic male traits correlated with female attraction: body condition, lek attendance, ornamental symmetry, and display rates.

Acoustic Parameters

For species that use vocal displays, record the acoustic parameters of male calls. In the houbara bustard, researchers investigated the similarity of boom acoustic parameters among captive males that were more or less individually inbred and therefore genetically related. They found that kin share similar frequency and temporal characteristics of their vocalizations. Recording these parameters can reveal information about male identity and quality.

Lek Attendance

Record which males attend the lek and for how long. Lek attendance was one of the traits correlated with female attraction in the little bustard. Males that attend the lek more consistently may be more attractive to females.

Common Failure Patterns in Lek Identification

Researchers and managers often make predictable errors when identifying exploded leks. Recognizing these failure patterns can improve study design and interpretation.

Mistaking Exploded Leks for Resource Defence

The most common error is confusing an exploded lek with resource defence polygyny. The distinction depends on whether females visit male territories for the male or for resources. If males defend territories that contain food or nesting sites that females need, the system is resource defence polygyny. If the only resource females find on the lek is the male, the system is a lek. The little bustard study specifically investigated this question by analyzing land use within male territories and found that resources were selected according to male needs instead of female needs.

Underestimating Lek Extent

Because exploded leks cover large areas, researchers may underestimate the number of males in the lek if they only survey a portion of the area. The capercaillie GPS telemetry study showed that males on exploded leks maintain spatial relationships over large distances, so surveys must cover the full extent of the lek to count all displaying males.

Overlooking Acoustic Signals

In exploded leks, males may be out of visual contact, so acoustic signals are critical for both female attraction and male spacing. Researchers who focus only on visual observations may miss the full extent of the lek. The houbara bustard study showed that male vocalizations convey information on kinship and inbreeding, which means acoustic recordings can provide data that visual observations cannot.

Assuming Kin Association

Researchers may assume that males on a lek are related, but this is not always the case. In the houbara bustard, there was no evidence for spatial structuring of males based on their acoustic parameters, which agreed with previous genetic findings on the absence of kin association within leks. Do not assume that males on an exploded lek are related without genetic data.

Welfare and Safety Context for Lek Observations

Observing exploded leks presents specific welfare and safety considerations for researchers and managers.

Minimizing Disturbance

Exploded leks cover large areas, so researchers may be tempted to use vehicles to move between male territories. Vehicle traffic can disturb displaying males and may cause them to abandon their territories. Approach display sites on foot whenever possible, and use blinds or natural cover to observe without being detected.

Breeding Season Sensitivity

The breeding season is a sensitive period for lekking species. Disturbance during this time can reduce mating success and may have population-level consequences. For endangered species like the little bustard, disturbance during the breeding season is a serious concern. Limit observations to the minimum needed to collect data, and avoid entering the lek during peak display hours.

Working With Captive Populations

For species like the Bulwer's wattled pheasant, captive populations provide opportunities to study behavior under controlled conditions. When housing potential lekking species in captivity, provide enough space for males to establish separate display territories. The study of captive Bulwer's wattled pheasants found that individuals may flock together in the nonbreeding season, so housing arrangements may need to change seasonally.

Safety Around Displaying Males

Some lekking species can be aggressive during the breeding season. Males may attack observers who approach too closely, and the large territories of exploded leks may make it difficult to predict where males will be. Maintain a safe distance from displaying males, and be aware that males may approach observers who enter their territory.

Limitations of Current Knowledge

Research on exploded lek mating systems has several limitations that affect how findings should be interpreted.

Taxonomic Bias

Research on lek mating systems has not kept pace with research on bats in general, and traditional typologies do not accommodate the mating system of several species. Most detailed studies of exploded leks have focused on birds, particularly bustards and grouse. The extent to which other taxa use exploded leks is unknown.

Definitional Challenges

A clear-cut definition of leks is difficult to obtain, and the four criteria for identifying a lekking species include conditions that are debated. The necessity of female mate choice as a criterion for lekking species has been highly debated. Different researchers may classify the same species differently depending on which criteria they emphasize.

Spatial Scale and Technology

Studying exploded leks requires tracking males and females over large areas, which has historically been difficult. GPS satellite telemetry has improved the ability to study species like the capercaillie grouse, but this technology is not available for all species or in all regions.

Captive Versus Wild Behavior

Captive studies can provide valuable data, but behavior in captivity may differ from behavior in the wild. The Bulwer's wattled pheasant study suggested that the species may have an exploded lek type of mating system in the wild, but this inference was based on captive observations. Confirming the mating system in the wild requires field studies.

Professional Escalation Criteria

Knowing when to escalate a finding to a specialist or authority is important for researchers and managers working with lekking species.

When to Consult a Behavioral Ecologist

If you observe a mating system that does not fit the traditional categories, consult a behavioral ecologist who specializes in mating systems. The functional framework proposed for bats includes a lek-like mating system category to account for cases that have the appearance of resource defence but are functionally akin to a lek. A specialist can help you determine which category applies to your study species.

When to Contact Wildlife Authorities

If you observe lekking behavior in an endangered species, contact the relevant wildlife authority. The little bustard is endangered, and research on its mating system has implications for conservation. Disturbance of breeding habitat may require permits or may be regulated by law.

When to Publish or Share Data

If your observations provide new information about a species' mating system, consider publishing your data or sharing it with researchers who study that species. The review of bat mating systems noted that research on bat mating systems has not kept pace with research on bats in general, which suggests that new observations are valuable.

Frequently Asked Questions

What is the main difference between a classic lek and an exploded lek?

The main difference is the distance between displaying males. In a classic lek, males display in tight aggregations where females can compare several males within a small area. In an exploded lek, male territories are spread out over a much larger area, often separated by hundreds of meters, so females must travel between territories to compare males.

Why do some species use exploded leks instead of classic leks?

Habitat constraints are a primary reason. When suitable display sites are patchy or when the habitat does not allow males to gather in tight aggregations, males may spread out while still maintaining the essential features of a lek. The little bustard study found that resources within male territories were selected according to male needs instead of female needs, which supports the lek interpretation.

How do females choose mates on an exploded lek?

Females may use alternative tactics, including a comparative assessment of males in a population, using one or several relative preference criteria. In the little bustard, at least four phenotypic male traits correlated with female attraction: body condition, lek attendance, ornamental symmetry, and display rates. Traits related to the initial female attraction to a male territory seem to differ from traits related to the decision to stay.

Which species are known to use exploded lek mating systems?

Known or suspected exploded lek species include the little bustard, houbara bustard, capercaillie grouse, and Bulwer's wattled pheasant. Some birds of paradise also use this system, and the wrinkle-faced bat is one of the few bat species documented to use lek courtship.

How large are exploded lek territories?

Territory size varies by species. Little bustard male territories averaged 19 hectares with a standard deviation of 16 hectares, and there was large among-male variability. The total area of an exploded lek can be several square kilometers even when the number of displaying males is similar to a classic lek.

Are males on an exploded lek related to each other?

Not necessarily. In the houbara bustard, there was no evidence for spatial structuring of males based on their acoustic parameters, which agreed with previous genetic findings on the absence of kin association within leks. Do not assume that males on an exploded lek are related without genetic data.

How do researchers study exploded leks?

Researchers map male display territories using GPS, measure distances between males, assess resources within territories, observe female behavior, and apply the four criteria for identifying a lekking species. GPS satellite telemetry has been used to study the spatial relationship of males on exploded leks in the capercaillie grouse.

What are the four criteria for identifying a lekking species?

The four criteria are: no male parental investment beyond sperm, males aggregate at specific sites for display, the only resource females find on the lek is the male, and females can select their mates. The necessity of the final condition has been debated.

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References and Further Reading

• NCBI Literature Resources. National Center for Biotechnology Information.
• PubMed. National Library of Medicine.
• Lek mating systems: a case study in the Little Bustard Tetrax tetrax.. Behavioural processes, 2000.
• Bat mating systems-A review and recategorisation.. Ecology and evolution, 2024.
• Behavior of captive Bulwer's wattled pheasants, Lophura bulweri (Galliformes: Phasianidae).. Zoo biology, 2001.
• Male vocalizations convey information on kinship and inbreeding in a lekking bird.. Ecology and evolution, 2019.
• Sexy males and choosy females on exploded leks: correlates of male attractiveness in the Little Bustard.. Behavioural processes, 2014.
• Explaining sex: contrast between social and sexual selection.. 2025.
• Comparative population genomics reveals convergent adaptation across independent origins of avian obligate brood parasitism. 2025.
• Cultural Transmission, Evolution, and Revolution in Vocal Displays: Insights From Bird and Whale Song.. 2020.
• The masked seducers: Lek courtship behavior in the wrinkle-faced bat Centurio senex (Phyllostomidae).. 2020.
• Display dispersion and diet of birds of paradise: a comparison of nine species. Behavioral Ecology and Sociobiology, 1983.
• Prediction of the spread of highly pathogenic avian influenza using a multifactor network: Part 1 - Development and application of computational fluid dynamics simulations of airborne dispersion. 2014.
• Exploded leks: What bustards can teach us. Ardeola, 2001.
• On the spatial relationship of males on "exploded" leks: The case of Capercaillie grouse Tetrao urogallus examined by GPS satellite telemetry. Ornis Fennica, 2013.
• Mating system of the Houbara Bustard Chlamydotis undulata undulata in eastern Morocco. Ardeola, 2005.

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.