To lek or not to lek: mating strategies of male fallow deer

We studied the mating system of fallow deer (Dama dama) for6 years in central Italy. Males in this population could defendterritories that were either single, clumped in leks, or satelliteto leks. The most highly successful males in our study werein leks. When we considered all males, there were no significantdifferences in average copulatory success according to territorytype because many lek males did not achieve any copulations,which were seen in only a few lek territories. The variancein copulatory success, however, was much greater for leks thanelsewhere. Single territories were occupied for shorter timesduring the rut than lek territories. Fighting among males wasmore frequent in the lek, even when we excluded highly successfullek males from the analysis. Chases of nonterritorial malesand harem size were correlated with the number of copulationsachieved by individual males, but did not vary according toterritory type. Copulatory success of some individuals increasedwith age, but there were no age differences among males holdingdifferent types of territories. Satellite males switched tolek territoriality in the course of one rut, but switches fromsingle territory to lek territory were rare. We suggest thatmales in single territories are inferior competitors that selecta low-risk, lowbenefit strategy, whereas those in lek territorieswhere no copulations were seen may be attempting to establishthemselves on the lek to increase their copulatory success infuture years.     

Mating strategies of topi bulls: getting in the centre of attention

In lek-breeding ungulates, only some males defend clustered lek territories, and others defend dispersed territories or are nonterritorial. In this study of lekking topi antelopes, Damaliscus lunatus, we measured male mating benefits directly by observing matings and investigated why the alternative mating strategies coexist. A multivariate analysis showed that proximity to the lek centre had an overriding, positive, effect on male mating rate. With increasing distance to the lek centre, proximity of a territory to a drainage line became increasingly important in enhancing male mating success. On the other hand, costs of lekking were suggested by higher hyaena density on leks, relatively poor body condition of lek males, and more frequent agonistic encounters, with central lek males more likely to sustain bleeding wounds than others. Probably as a consequence of the intense competition for central lek territories, males defending such territories were larger than others and, judging from horn wear, they were also older than resource defenders. Not only did males defending central lek territories achieve the highest instantaneous mating rate and resource defenders the lowest, but the same order was also likely for overall lifetime reproductive success when we took territorial tenure into account. These results suggest that male mating strategies are phenotype limited, as demands on male quality increase with proximity to the lek centre. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Mate choice or harassment avoidance? A question of female control at the lek

Recent studies on the reproductive behavior of fallow deer,Dama dama, propose that harassment from nonterritorial maleshas a major influence on female movements and mate selection,leading ultimately to the evolution of lek mating in this species.In order to support this statement, one must demonstrate thatfemale movements between lek and isolated territories, and amonglek males, lead to a reduction in levels of harassment. We arguethat current evidence in favor of this view is inconclusive.A quantification of the total harassment costs experienced byfemales in lek and isolated territories has never been made.In addition, female movements within the lek may actually leadto higher levels of disruption and harassment: The rate at whichfemales join male territories increases with harem size (thenumber of females present in the territory), even though haremsare disrupted increasingly with size due to a higher frequencyof intrusions by nonterritorial males. Females also join maleterritories at a higher rate while these males are engaged incopulatory sequences, but copulatory sequences are again associatedwith high levels of disruption and harem instability. In theabove studies it is argued that females are nonselective intheir mating preferences. This assessment is based on the findingthat males that adopt different reproductive strategies do notdiffer in their mating rates. Here mating rate is measured asthe number of copulations received per female-hour. There area number of reasons, however, why females exhibiting matingpreferences might remain longer with preferred males, and sothe above preference measure cannot be used to exclude the possibilitythat females are selective. More research is required to identifythe major factors influencing patterns of mate selection andthe evolution of leks in this species. We suggest a number offield tests that may help to identify these factors.     

Aggression among Lekking Male Fallow Deer (Dama dama): Territory Effects and Relationship with Copulatory Success

We studied the aggressive behavior of territorial male fallow deer (Dama dama) at two leks. Daily number of escalated fights was not correlated with number of matings. A dominance index including all agonistic interactions was weakly correlated with copulatory success; the correlation was stronger when each half of the rut was considered separately. Dominance likely changed over the rut due to fatigue. We ranked lek territories by the number of copulations seen in each. Males that won fights were likely to take over the loser's territory only if it ranked higher than the one they held. Winners were more likely to fight with a third male after defeating an opponent that held a higher-ranking territory than one from a lower-ranking territory. Exposure to attacks by third-party males may be a major cost of fighting. Males appear aware of the relative value of different lek territories, but the frequency of aggression was not scaled to potential fitness benefits, possibly because males seldom fought with opponents they were unlikely to beat. The outcome of interactions on the lek may not always reflect the relative dominance rank of the contestants. Females are unlikely to use the outcome of fights as a direct criterion for mate selection.     

INTRASEXUAL COMPETITION ALONE FAVORS A SEXUALLY DIMORPHIC ORNAMENT IN THE RUBYSPOT DAMSELFLY HETAERINA AMERICANA

I studied the sex-limited red spots on the wings of male rubyspot damselflies (Hetaerina americana) in relation to territoriality and fitness in the wild. Both observational and experimental (wing spot manipulation) studies indicated that wing spots were selected through competition among males for mating territories, not through female choice or direct competition for females. Males with naturally or artificially large wing spots were more successful at holding territories and consequently mated at higher rates than males with relatively small wing spots. In contrast, sexual selection on male body size appeared to operate among nonterritorial males at the clasping stage of the mating sequence, perhaps because larger males were better at clasping females forcibly. Of four models proposed to explain the evolution of ornaments through territory competition, only the agonistic handicap model makes predictions consistent with the results of this study.     

No peace for estrous topi cows on leks

Male coercion, such as harassment, may be considered the thirdmain component in sexual selection alongside male competitionand female choice. In this study on lek-breeding topi antelopes(Damaliscus lunatus), I investigate whether female mating preferenceshave consequences for male investment in harassment and whetherharassing males are more likely to succeed in mating. I thenaddress the question of whether lek evolution in topi can beexplained by harassment avoidance. Judging from mating rate,I found that female topi antelopes in estrus preferred lek malesto resource defenders. In contrast to lek males, resource defendersdemonstrated significantly higher harassment rates before theysucceeded in mating than when they did not, and the precopulatoryharassment rate was significantly higher on resource territoriesthan on lek territories. After mating on resource territories,harassment dropped to low levels. Thus, resource defenders,but not lek males, seem to employ harassment as a strategy tocoerce females to mate against their preference. However, byusing various measures of harassment intensity, overall estrousfemales were found to experience higher harassment levels onlek, and chases by intruders were relatively rare on all territorytypes. These findings suggest that harassment avoidance is unlikelyas an explanation for lek evolution.     

Physiological costs enforce the honesty of lek display in the black grouse (Tetrao tetrix)

Females may use condition-dependent sexual traits as reliable cues of male “quality” if the costs of the expression of such traits vary with male “quality”, and if there is positive genetic correlation between male traits and condition. However, there are multiple ways of measuring the changes in body condition which reflect physiological costs meaning that the multifaceted nature of the physiological costs associated with the expression of sexual traits has rarely been thoroughly examined. In the lekking black grouse (Tetrao tetrix), mating success is highly skewed towards males defending central territories and having high survival rates to the following year, but the mechanisms underpinning such superior performance remain unclear. In this study, we quantified the changes in five measures of body condition before and after the mating season and related these changes to male lek performance (fighting rate, territory centrality and mating success) to understand the physiological costs of male reproductive effort. Between the two capture sessions, male body mass decreased significantly, blood parasite counts and plasma carotenoid concentration increased substantially while the total immunoglobulin concentration tended to increase. There was no overall impairment of individual body condition as the changes in the five measures of body condition were unrelated. Male fighting rate was unrelated to changes in the condition measures but males losing more body mass defended central territories and had high mating success. Therefore, females preferring central, dominant males may select males better able to afford the energetic costs of lek performance thereby effectively enforcing the honesty of male display.     

Queuing in space and time reduces the lek paradox on an antelope lek

Lek systems, where females often use centrality to assess male quality, highlight a general paradox in evolutionary biology: how can female preferences for males providing good genes persist when consequential strong directional selection is predicted to deplete additive genetic variance in male quality and thereby obliterate benefits of choosiness? An explanation contributing to the resolution of this lek paradox may be that genetic variance is retained when an indirect mate choice cue, such as centrality on a lek, is an imperfect indicator of male genetic quality. Here I investigate whether the presence of alternative male mating tactics limits the reliability of centrality as a quality indicator in lek-breeding topi antelopes. Whereas males establishing territories directly on the central lek were relatively large, smaller peripheral males regularly shifted their territories centripetally and in this way also occasionally obtained central territories. By such opportunistic queuing, small males could increase their mating success drastically; however, their territorial tenure in the lek centre was relatively short, consistent with moderate competitive ability. These results suggest that male topi antelopes can obtain central lek territories through alternative mating tactics, providing scope for variance in male quality on the central lek. In a separate finding, the mating success of central males was found to increase during territorial tenure, independent of estimated age. The demonstration of queuing in both space and time on a mammalian lek highlights the importance of considering male tactical dynamics over time in order to avoid an inflated appearance of the lek paradox.     

Chorus organization and male mating behavior in the Japanese pond frog,Rana porosa brevipoda

Male mating behavior of a Japanese pond frog,Rana porosa brevipoda, was observed in an enclosed pond. Males organized chorus aggregation during the night. Within the chorus, most males defended “floating” territories. Territorial males exhibited 2 types of calls: advertisement and encounter. Mating occurred primarily in male territories with female initiation, while most spawning occurred outside of the territories. After spawning, males returned to their territories and resumed display behavior. The mating system of this frog is analogous to the typical lek system. Alternative male mating tactics, including satellite and ambush behavior, were also observed. Satellite and ambush males mated with females through forced clasping.     

Reproductive success in male Japanese minnows,Pseudorasbora parva: observations under experimental conditions

To evaluate the spawning success of male Japanese minnows,Pseudorasbora parva, and female mate choice, spawning behaviour was observed under both artificial and experimental conditions. Larger males had larger territories and greater reproductive success. The body weight of territorial males decreased during the maintenance of territories, while that of non-territorial males increased significantly. When the weight of non-territorial males exceeded that of territorial males, the former began to establish new territories on the substrate, suggesting a conditional strategy by non-territorial males to trade off immediate reproductive success with growth and hence improve future reproductive success. Females chose males with larger body size, probably based on dominance rank rather than the quality (or size) of territory. It was concluded that females choose males of higher dominance rank and that males compete for large territories, both of which play an important part in male reproductive success.     

How predation risk affects the temporal dynamics of avian leks: greater sage grouse versus golden eagles

Leks often attract predators as well as mates, yet most evolutionary models have assumed that sexual selection, not predation, drives lekking behavior. We explored the influence of predation on lek dynamics using a stochastic dynamic game model based on the lek-breeding greater sage grouse (Centrocercus urophasianus) and its principal avian predator, the golden eagle (Aquila chrysaetos). The model predicts time-dependent male lek attendance as a function of factors affecting both mating success (female arrival rate, male numbers, and social status) and predation risk (eagle arrival rate and group size). Dominant males are predicted to arrive sooner and leave later than subordinates, especially if mating skew is high, predation risk is low, or the relationship between lek size and female arrival rate is weak. Both high mean levels of predation risk and small lek size should reduce lek attendance, but the relative tendency of predators to attack large versus small leks has little influence on predicted lekking behavior. Field observations confirmed the predicted effects of female arrival rate, lek size, male dominance, and weather-dependent predator arrival rates on lek departure times. Predicted effects of female arrival rates and male dominance on seasonal lek attendance were also supported. Our model provides an empirically supported adaptive explanation for short-term lek dynamics. It also suggests alternative interpretations for phenomena previously invoked to support the hotshot and skew models of lek formation.     

Habitat Manipulation Modifies Lek Use in Fallow Deer

Fallow deer leks and single territories often persist in specific locations over many years. In our study area in Tuscany, one site (Lek 1) was used as a lek by fallow deer for at least 30 years. Females passed through the lek year-round while travelling between sheltering and foraging sites. In 1987–89, forestry operations affected areas near the lek that were used by females as travel routes, but the lek site itself was not affected. After the logging operations, very few females traversed the lek site. Over the next 2 years the lek decreased in size (both in terms of number of territories defended and number of territorial males) until it became a single territory, and after two more years it was abandoned. Another lek (Lek 2) whose access routes were unaffected by forest cuts, continued to exist. Territorial males abandoned Lek 1 and moved to Lek 2 when female visits to Lek 1 became rare. Our results suggest that female movement patterns can be affected by habitat manipulations, and that females will not return to traditional mating sites that become external to their home ranges. Male fallow deer may form leks along female movement routes, where they experience a high female encounter rate as predicted by the hotspot model.     

Evolution of black grouse leks: female preferences benefit males in larger leks

Leks, communal display grounds in which males display and femalesonly attend to mate, represent one of the most remarkable outcomesof sexual selection. There have been no detailed studies thatcompare the behavior of males and females between leks of differentsizes to test if there is any benefit for male clumping andto test the many hypotheses suggested to explain lekking. Inthe black grouse, Tetrao tetrix, larger leks have many morefemale visits and copulations, leading to a higher average malemating success. Females visiting larger leks are also more likelyto mate, indicating that female preferences of males are importantfor the evolution of leks. Yearling males seldom copulate, buttheir presence on the lek increases the mating success of adultmales, suggesting that lek size per se and not only male qualityaffects female preferences for larger leks. The distributionof males over lek sizes agrees with a game theory model of idealfree distribution with unequal competitors, in which less competitivemales go to smaller leks.     

Mate retention, harassment, and the evolution of ungulate leks

Current models of lek breeding mostly suggest that males defendclustered mating territories because females show a preferencefor mating on leks. Here we argue that, in lek-breeding ungulates,males may also gain benefits from holding clustered mating territoriesbecause clusters retain does in estrus. We show that in fallowdeer (Dama dama) harems are commonly disrupted by young males.Bucks that hold territories on the lek that lose their haremsquickly regain does as other harems are disrupted, whereas bucksdefending isolated, single territories rarely regain does thesame day. The risk of harassment may also help to explain whydoes in estrus leave the large, unstable herds that they usuallylive in. Does in estrus are frequently chased by young maleswhen outside male mating territories. Benefits of moving tothe lek (versus moving to single territories) include reducedrisks of long chases. Though intrusions by young bucks are thecommonest cause of does leaving male territories in our studypopulation, other factors that cause does to move between neighboringharems (including disturbance by predators and persistent courtshipby males) may generate benefits to males holding clustered matingterritories. Once clustered mating territories have developed,the additional costs of mate choice are likely to be low, andfemale preferences for particular male characteristics may belikely to develop.     

Male territoriality and mating system in the European beewolf Philanthus triangulum F. (Hymenoptera: Crabronidae): evidence for a “hotspot” lek polygyny

The evolution of the mating system of a species is strongly influenced by the spatial and temporal distribution of females and/or resources. Here, we describe aspects of the territorial behavior of males of a solitary digger wasp, the European beewolf (Philanthus triangulum) and characterize the mating system. We show that beewolf males establish small territories that do not contain any resources essential to females. These territories are intensively scent-marked with a pheromone from a cephalic gland and are defended against intruders in combat flights. We provide evidence that scent-marking constitutes a chemical display and that the pheromone serves to attract receptive females and, thus, represents a sex pheromone. Using spatial statistics, we show that beewolf territories are clumped in space both with respect to other male territories and, more importantly, with respect to female nesting sites. Additionally, the proportion of days a territory is occupied by a male is correlated with the number of female nests in the vicinity. Taking into account that beewolf males do not defend or provide resources essential to females, but merely display chemically to attract females for mating in an aggregation of territories close to female nesting sites, we conclude that the European beewolf exhibits a hotspot lek polygyny with female nesting sites constituting “hotspots” for lek formation.     

Lek mating systems: a case study in the Little Bustard Tetrax tetrax

Leks have recently been defined as male display aggregations that females attend primarily for the purpose of mating. This is an extended version of previous definitions, as a clear-cut definition of leks is difficult to obtain. Four criteria should be verified to identify a lekking species: (i) there is no male parental investment beyond the sperm; (ii) males aggregate at specific sites for display; (iii) the only resource females find on the lek is the male, i.e. the male genes; (iv) females can select her mate(s), although the necessity of this latter condition for lekking species has been highly debated. We applied these criteria to the endangered little bustard Tetrax tetrax, a species that is claimed to show an exploded lek mating system, but for which this has never been fully investigated. We monitored a population of little bustards in western France during 2 years to investigate the two central criteria in the assessment of their mating system: male aggregation in arenas and lack of consistent resources in male territories. We analysed the spatial distribution of little bustard male territories, the individual variation in size, and the land use characteristics of male territories, with particular attention to the habitats that may be considered as defensible resources. Displaying males showed an aggregated spatial distribution over the study area during the 2 years of survey. Male territories were rather large (19+/-16 ha), but a large among-male variability in territory size was observed. Land use within the territories included mainly permanent and semi-permanent crops. The variability in land use among territories suggests also that resources found within male territories were selected according to male needs (food and display) rather than to female needs (permanent crops that are more appropriate for reproduction). The mating system of the little bustard seems to match the general (and extended) definition of leks, at least in some populations. However, limits between resource defence polygyny and extreme exploded or resource-based leks are thin and unclear, and the little bustard is a good example of how lek definitions may be difficult to apply in non clear-cut empirical situations.     

Correlates of male mating success and female choice in a lek-breeding antelope

We investigated factors underlying variation in male matingsuccess in Uganda kob (Kobus kob thomasi), a lek-breeding antelope.We found that only heavy (and, possibly, relatively old) malesheld lek territories and that female choice was an importantdeterminant of nonrandom mating patterns at leks. Our measureof male mating success was closely related to the historicalpopularity of the territory that a male defended, and individualfemales showed consistent preferences for particular lek territories,despite changes in territory ownership. Male success increasedwith body weight and declined independently of territory effectsduring each bout of lek territory tenure. We also found someevidence that female kob copied one another's choice of matesbecause females arriving at a lek tended to join territoriesthat already had relatively large harems on them. When comparedacross leks, average male mating success increased with leksize. Our results suggest that female kob may use a suite ofmale- and territory-based cues in mate choice at leks and, asa result, mate with particularly large males. However, we wereunable to determine whether female kob gain any direct or indirectbenefits through mate choice at leks.     

Size and mating success in males of the western harvester ant,Pogonomyrmex occidentalis (Hymenoptera: Formicidae)

Mating success in males of the lek mating ant species,Pogonomyrmex occidentalis, increases with increased body size. We estimated the magnitude of the selection coefficients on components of size by collecting males in copula and comparing their morphology to that of males that were collected at the lek but that were not mating. Four characters, body mass, head width, wing length, and leg length, were measured for a sample of 225 mating and 324 nonmating males and 225 females. Significant direct selection favors increased wing length and leg length. Multiple regression of transformed variables (principal components) indicated that the increased mating success of larger males is a function of all four characters. We found no evidence of positive assortative mating on the basis of any individual character or on the multivariate general size variable (the first principal component).     

When should males lek? Insights from a dynamic state variable model

A central focus in the study of lek evolution is to understandthe clustering of male mating territories. Lekking males typicallydefend small clumped territories and experience intense competitionassociated with dense aggregations. We used dynamic state variablemodeling to evaluate three alternative selective pressures proposedto explain the evolution of lekking. These are female matingbias for large clusters, reduction in predation risk in largeclusters, and male harassment of estrous females. We modeledmale mating decisions during a single breeding season usinga lekking ungulate as a model system. Males could choose fromeight alternative tactics that included a nonreproductive tactic,territorial tactics ranging from low to high clustering, andthe option to join a mixed-sex herd. The model predicted a state-and time-dependent strategy that maximizes mating success overthe course of the season. We then simulated a population of100 males that used the optimal strategy and calculated theproportion of the population that adopted each tactic. Our modelgenerated unique predictions for the three selective pressureswe considered. Female mating bias, when nonlinearly relatedto cluster size, had the greatest potential to generate largeclusters of territorial males, whereas predation risk and harassmentof females typically did not promote male clustering. More generally,our model highlights the conditions that will favor lekking.Lek-like clustering was consistently produced when the benefitsin clustering increased in specific nonlinear ways. Our modelthus emphasizes clarifying the shapes of relationships betweenpotential selective factors and the size of territory clusters.     

Lek behaviour of Drosophila cnecopleura in Hawaii

ABSTRACT.

• 1 Male spacing, aggression, and female visitation are described for a lek of Drosophila cnecopleura Hardy within a Hawaiian rainforest. The lek was located at a single tree of Pisonia umbellifera, and the males present defended individual leaves as mating territories. Observations were made in October 1986 and April 1987.
• 2 Approximately twice as many males were present at the lek in October than in April. At both times, males generally perched on the lowest leaves in the lek. Individuals did not remain on particular leaves for long periods of time but frequently moved among different territories.
• 3 Males engaged in two types of aggressive encounters, face-offs and chases, and in all encounters the resident displaced the intruder.
• 4 Females were sighted at the lek 0.69 times/h in October and 0.23 times/h in April. Most of the leaves visited by females were among the lowest in the lek.