Modelling environmental and survey influences on lek attendance using long‐term lek survey data

Targeted lek surveys, in which historically active lekking areas are surveyed over multiple years, are commonly used to monitor lek‐mating birds. Lek surveys are usually used in habitats and species in which individuals are not easily detected when they are not lekking. Unfortunately, lek surveys suffer from a number of shortcomings, most notably the failure to observe lekking individuals when they are near but not actively attending a lek. Like other sources of imperfect detection, inconsistency in lek attendance may bias estimates of annual population sizes or the proportion of lekking arenas active in a given year. In turn, this may result in unreliable estimates of trends, distributions or other parameters of interest. An improved understanding of the factors affecting lek attendance is crucial to improving the efficacy of many lek monitoring programmes and the utility of lek surveys in estimating population and distributional dynamics. We assess variation in lek attendance in the Lesser Prairie Chicken Tympanuchus pallidicinctus using a subset of data from a long‐term monitoring programme in eastern New Mexico, USA. Focusing on lek‐years in which at least one male was observed, we used generalized linear models to assess the influence of lek size and survey and environmental characteristics on the probability that at least one male was observed in attendance. Our best‐supported model provided evidence for influences of each of these sources of variation. Models suggested that surveyors may improve the likelihood of detecting lek attendance by making small changes to survey duration, targeted survey dates and by considering environmental factors such as weather, habitat and human disturbance. In addition to improving detection, consideration of lek attendance patterns and associated behaviours may improve estimation for more effective conservation in a variety of lekking bird species.     

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.     

Absence of male reproductive skew,along with high frequency of polyandry and conspecific brood parasitism in the lekking Houbara bustard Chlamydotis undulata undulata

Behavioural studies have led to the perception that lekking species experience a high male reproductive skew as a consequence of females’ selective mate choice. In addition, observations suggest that females copulate only once and therefore polyandry seems unlikely as females are supposed to choose the best male available. In order to analyse the mating strategy of the Houbara bustard, an endangered lekking species under reinforcement in eastern Morocco, we used microsatellite data to perform paternity analyses. None of our observations followed common expectations under a lek mating system: we found no male reproductive skew suggesting no apparent selective female mate choice and no apparent male benefit from lekking. In contrast, a high level of polyandry (60 % of the nests) was recorded suggesting that sperm competition may operate. In addition, we present another case of conspecific brood parasitism in a lekking species and this was an unexpected alternative strategy for a species presenting high parental cost and low fecundity. The increasing number of studies contradicting common assumptions on lekking species suggests that alternative breeding strategies such as males pursuing an off‐lek mating strategy, female polyandry and even conspecific brood parasitism might be more widespread in lekking species than previously thought.     

Size and stability of vertebrate leks

Lek size varies greatly among lekking species. At present there is no explicit theoretical explanation for this diversity. We extend an existing model of optimal lek size that incorporates female mating preferences and male-male contest competition. The model shows that variation in lek size is predicted by the interaction between lek size, overall copulation rate and the proportion of copulations accruing to males of different rank. In species where females prefer to mate on the largest leks and high-ranking males are able to monopolize females irrespective of the size of the lek, the maximum lek size will be large. Conversely, in species where females show weak preference for mating on large leks or increasing lek size quickly results in scramble competition, the maximum lek size will be smaller. Thus, differences between species in lek size may be due largely to differences in the extent to which high-ranking males can monopolize mating opportunities. Leks become unstable and break down when high-ranking males can no longer get their 'expected' copulation success. Therefore, the mechanism that generates male clustering, that is, sexual parasitism of high-ranking males by subordinates, also sets a limit to the largest stable lek size. Copyright 1999 The Association for the Study of Animal Behaviour.     

Risk induced by a native top predator reduces alien mink movements

1. Nonlethal predation effects may have stronger impacts on prey populations than direct predation impacts, and this should also apply to intraguild predation. The consequences of such interactions become especially important if invasive, and potentially destructive alien predators act as intraguild prey. 2. We studied the predation-risk impacts of a re-colonizing native top predator, Haliaeetus albicilla (white-tailed sea eagle), on the movements of Mustela vison (American mink), an alien predator in Europe. We radiocollared 20 mink in two study areas in the outer archipelago of the Baltic Sea, South-west Finland, during 2004 and 2005. In the archipelago, mink home ranges incorporate many islands, and mink are most predisposed to eagle predation while swimming between islands. Observed swimming distances of mink were compared to distances expected at random, and deviations from random swimming were explained by mink distance from nearest eagle nest, number of eagle observations near mink location, and mink home-range size. 3. Mink reduced their swimming distances with increasing sea eagle predation risk: for females, the reduction was 10% for an increase of 10 eagle observations, and 5% for each kilometre towards an eagle nest. Conclusions for males were restricted by their small sample size. 4. Our results suggest that female mink modify their behaviour according to eagle predation risk, which may reduce their population growth and have long-term cascading effects on lower trophic levels including bird, mammal and amphibian populations in the archipelago. Ecosystem restoration by bringing back the top predators may be one way of mitigating alien predator effects on native biota.     

Induced changes in island fox (Urocyon littoralis) activity do not mitigate the extinction threat posed by a novel predator

Prey response to novel predators influences the impacts on prey populations of introduced predators, bio-control efforts, and predator range expansion. Predicting the impacts of novel predators on native prey requires an understanding of both predator avoidance strategies and their potential to reduce predation risk. We examine the response of island foxes (Urocyon littoralis) to invasion by golden eagles (Aquila chrysaetos). Foxes reduced daytime activity and increased night time activity relative to eagle-na?ve foxes. Individual foxes reverted toward diurnal tendencies following eagle removal efforts. We quantified the potential population impact of reduced diurnality by modeling island fox population dynamics. Our model predicted an annual population decline similar to what was observed following golden eagle invasion and predicted that the observed 11% reduction in daytime activity would not reduce predation risk sufficiently to reduce extinction risk. The limited effect of this behaviorally plastic predator avoidance strategy highlights the importance of linking behavioral change to population dynamics for predicting the impact of novel predators on resident prey populations.     

Lek mating system and its impact on male annihilation technique

Simulation models were presented which describe the matings inside a lek. The size of the lek was assumed to follow a poisson distribution, the dominance factor of each of the males was drawn from a gamma distribution, and the mating probability for each male was determined by its mating effectiveness raised to female mating factor divided by the sum of all the mating effectivenesses raised to this power. The mating probatility for each male and the actual matings were determined by Monte Carlo simulation. Based on the simulation data, the effects of female mating factor and size of the lek on the frequency of actual matings accomplished by the males inside the lek were discussed. In the case of male annihilation, the mean number of effective matings per male in the lek, calculated from the frequency of actual matings weighted by the effective mating ratio, was used to evaluate the efficiency of male annihilation method.     

Indirect Effects of an Existing Wind Energy Facility on Lekking Behavior of Greater Prairie‐Chickens

Rapid expansion of the wind energy industry has raised concerns about the potential effects of anthropogenic disturbance on prairie grouse. While efforts have been made to address the effects of wind energy facilities on measures of fitness, their effect on the behaviors of prairie grouse has been largely neglected. To address these concerns, we investigated the effects of an existing wind energy facility in Nebraska that became operational in 2005 on the lekking behavior of male greater prairie‐chickens Tympanuchus cupido pinnatus between March and May 2013. Given the potential for disturbance caused by wind turbine noise to disrupt acoustic communication and thus behavior, we predicted that males at leks close to, compared to far from, the wind energy facility would spend more time in agonistic behaviors, and less in booming displays. Given the potential for wind turbine noise to reduce the number of females attending leks (hereafter ‘female lek attendance’), we also predicted that males at leks close to the wind energy facility would spend more time in non‐breeding behaviors and less time in breeding behaviors than males farther from the facility. Although we found no effect of the wind energy facility on female lek attendance, males at leks closer to the wind energy facility spent less time in non‐breeding behaviors than those at leks farther away. However, distance from the wind energy facility had no effect on time spent performing booming displays, flutter jumps, or in agonistic behaviors. Given that lekking behaviors of males influence mating success, our results may have consequences for the fitness of prairie grouse breeding in the vicinity of wind energy facilities.     

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.      

The costs of female choice in a lekking bird

We investigated the costs of active female choice in sage grouse,Centrocercus urophasianus, a lekking species in which femalesmake repeated, lengthy visits to leks to assess males beforemating. Several potential costs were measured by monitoringchanges in hens' ranging behavior, time budgets, and encounterrates with predators when they visited leks. Two costs wereidentified: hens moved further per day and encountered goldeneagles, Aquila chrysaetos, more frequently when visiting leks.However, extra travel due to visiting leks increased predicteddaily energetic expenditure by only about 1%, and the risk ofpredation by golden eagles over a typical series of lek visits(compared to a single short visit for mating) was estimatedto reduce annual survival by <0.1%. Two other potential costswere not supported: visiting leks did not depress foraging timeor conflict with nest defense. These results indicate that anycosts of mate choice are slight and imply that even very smallbenefits could be sufficient to maintain female choice. We presentcalculations which suggest that increased offspring viabilitydue to choosing fitter males could balance predation costs evenif the heritability of fitness is low and if females identifyfitter males with only moderate accuracy. Despite recent emphasison the direct benefits of mate choice, we conclude that eitherindirect or direct benefits could provide a plausible solutionto the lek paradox.     

Testing predictions for the evolution of lekking in the sandfly, Lutzomyia longipalpis

We carried out a combination of field and laboratory experiments to investigate two possible mechanisms promoting the evolution of lekking in the sandfly, Lutzomyia longipalpis. Males in this species lek on or near hosts that females visit to mate and feed. To test whether the distribution of resources, lek size and female number were positively correlated (a prediction of hotspot models) we manipulated the availability of potential lek sites by varying the numbers of chickens, Gallus gallus domesticus, held in field cages. We then investigated the distribution of males and females across leks formed within these cages and measured males to assess the relationship between male size and lek size. The number of males attracted to a lek increased with the number of hosts present and on average males on larger leks had longer abdomens. The number of females was positively correlated with the number of males present, but the average number of females per male decreased with increasing lek size. In a second experiment, we introduced single females to laboratory leks of different sizes, and compared female latency to mate. Contrary to an explicit prediction of the black hole model, lek size had a direct effect on a female's latency to mate. Females at larger leks encountered and copulated with males sooner than those at smaller aggregations, but the length of time a pair spent courting did not vary with lek size. Our results suggest that the black hole model is unlikely to explain the evolution of lekking in this species. The data instead support the hotspot model as a possible mechanism promoting lekking in L. longipalpis but suggest that female preference for larger leks may need to be invoked to obtain the degree of aggregation observed.     

Plumage brightness predicts male mating success in the lekking golden-collared manakin, Manacus vitellinus

The evolution of colorful plumage has been dramatic in lekkingspecies. Several studies show that the size of colorful traitsinfluence female choice in leks; however, relatively littleis known about the specific function of color, in particularits spectral properties, in lekking taxa. To determine the importanceof color in a lekking species, we monitored the mating successof male golden-collared manakins, Manacus vitellinus, and relatedthis to spectral measures of their colorful plumage, as wellas other morphological and behavioral traits shown to be importantin other lekking species. We found that lek centrality, malebody size, and plumage brightness were associated with malemating success. Only plumage brightness, however, entered amultiple regression model, indicating that plumage is the overallbest predictor of mating success. These results provide evidencethat the spectral properties of colorful plumage predict malemating success in a lekking species and provide important insightinto why many lekking birds are dichromatic and elaborate incoloration.     

Evolution of sexual size dimorphism in grouse and allies (Aves: Phasianidae) in relation to mating competition,fecundity demands and resource division

Sexual size dimorphism (SSD) is often assumed to be driven by three major selective processes: (1) sexual selection influencing male size and thus mating success, (2) fecundity selection acting on females and (3) inter‐sexual resource division favouring different size in males and females to reduce competition for resources. Sexual selection should be particularly strong in species that exhibit lek polygyny, since male mating success is highly skewed in such species. We investigated whether these three selective processes are related to SSD evolution in grouse and allies (Phasianidae). Male‐biased SSD increased with body size (Rensch’s rule) and lekking species exhibited more male‐biased SSD than nonlekking ones. Directional phylogenetic analyses indicated that lekking evolved before SSD, but conclusions were highly dependent on the body size traits and chosen model values. There was no relationship between SSD and male display agility, nor did resource division influence SSD. Although clutch mass increased with female body size it was not related to the degree of SSD. Taken together, the results are most consistent with the hypothesis that lekking behaviour led to the evolution of male‐biased SSD in Phasianidae.     

Assessing lek attendance of male greater sage-grouse using fine-resolution GPS data: Implications for population monitoring of lek mating grouse

Counts of males displaying on breeding grounds are the primary management tool used to assess population trends in lekking grouse species. Despite the importance of male lek attendance (i.e., proportion of males on leks available for detection) influencing lek counts, patterns of within season and between season variability in attendance rates are not well understood. We used high-frequency global positioning system (GPS) telemetry data from male greater sage-grouse (Centrocercus urophasianus; n = 67) over five lekking seasons (2013–2017) at eight study sites in Nevada to estimate lek attendance rates. Specifically, we recorded daily locations of sage-grouse in relation to mapped lek boundaries and used generalized additive models to assess temporal variation in attendance rates by age class (subadult vs. adult). Average timing of peak attendance occurred on 16 April but varied from March 16, 2014 to April 21 , 2016. Overall, adult males attended leks at higher rates (0.683 at peak) and earlier in the season (19 March) than subadults (0.421 at peak on April 19). Peak attendance probability was positively related to cumulative winter precipitation. Daily probabilities of lek switching differed between adults (0.019 at peak on March 3) and subadults (0.046 at peak on March 22), and lek switching was negatively related to distance to nearest lek. Our results indicate variable patterns in lek attendance through time, and that lek switching may occur at higher rates than previously thought. We demonstrate the use of generalizable daily attendance curves to date-correct lek counts and derive estimates of male abundance, although such an approach will likely require the incorporation of information on age structure to produce robust results that are useful for population monitoring.     

Non-random mating in classical lekking grouse species: seasonal and diurnal trends

This paper is the first to integrate both field and theoretical approaches to demonstrate that fertility benefits can be a direct benefit to females mating on the classical lek. Field data collected for male sharp-tailed grouse (Tympanuchus phasianellus), a classical lekking species, revealed potential fertility benefits for selective females. Adult males and individuals occupying centrally located territories on the lek were found to have significantly larger testes than juveniles and peripheral individuals. Further, using empirical data from previously published studies of classical lekking grouse species, time-series analysis was employed to illustrate that female mating patterns, seasonal and daily, were non-random. We are the first to show that these patterns coincide with times when male fertility is at its peak. Received: 26 February 1999 / Revised: 13 December 1999 / Accepted: 15 March 2000     

Fishing spiders, green sunfish, and a stream-dwelling water strider: male-female conflict and prey responses to single versus multiple predator environments

Many studies have experimentally addressed the effects of a particular predator species on prey behavior. In nature, however, prey frequently face multiple species of predators that often vary in their predatory mode and in their level of predation risk. Relatively few studies have considered prey responses under these complex conditions. In Kentucky, the stream-dwelling water strider (Aquariusremigis) coexists with many potentially dangerous predators, two of which are the green sunfish (Lepomiscyanellus) and the fishing spider (Dolomedesvittatus). Green sunfish occupy stream pools and attack water striders from below. In contrast, fishing spiders hunt along stream shorelines where they perch on overhanging vegetation or rocks and attack water striders near shore. We compared how A. remigis individuals respond to these two very different predators in pools with one or both predators. The presence of sunfish in pools had strong effects on male water strider behavior, including increased use of three types of refuge from sunfish (riffles, climbing out of the water, sitting on the water but at the edges of pools), decreased activity and a decreased number of aggressive males on the water. Spiders also influenced water strider behavior; male water striders avoided spiders by shifting away from the edges of pools. Comparisons of the effects of the two predator species showed that in general, antipredator responses by male water striders were stronger in pools with fish alone than in those with spiders alone. In the presence of both predators, male water strider behavior (microhabitat use and activity) was generally similar to behavior in the presence of fish alone. In contrast, female water striders showed no significant response to the presence of sunfish, and little response to the presence of spiders. This lack of response could be because females spent much of their time in refuges even in the absence of predators (apparently hiding from harassment by males). Both spiders and fish caused decreases in water strider mating activity. The presence of fish reduced both the number of matings per pool (mating frequency), and mean mating durations. Spiders induced a decrease in mean mating duration, but not in mating frequency. The largest reductions in mating activity occurred in pools with both predators present. Pools with either spiders or fish alone suffered 15–20% water strider mortality during our experiment (versus no mortality in predator-free pools). Extant theory suggests that when prey face conflicting microhabitat responses to two predators (as in this study), the predators should have facilitative effects on predation rates (i.e., prey that avoid one predator are often killed by the other and vice versa). Mortality rates in pools with both predators present, however, were not significantly different from that predicted by a null model of multiple predator effects. The lack of predator facilitation can be explained by the compensatory reductions in water strider activity and mating activity in the presence of both predators. Received: 26 August 1996 / Accepted: 12 June 1998     

Sacrificial males: the potential role of copulation and predation in contributing to copepod sex‐skewed ratios

Predation is thought to play a selective role in the emergence of behavioural traits in prey. Differences in behaviour between prey demographics may, therefore, be driven by predation with select components of the population being less vulnerable to predators. While under controlled conditions prey demography has been shown to have consequences for predation success, investigations linking these implications to natural prey population demographics are scarce. Here we assess predator–prey dynamics between notonectid predators (backswimmers) and Lovenula raynerae (Copepoda), key faunal groups in temperate ephemeral pond ecosystems. Using a combination of field and experimental approaches we test for the development and mechanism of predation‐induced sex‐skewed ratios. A natural population of L. raynerae was tracked over time in relation to their predator (notonectid) and prey (Cladocera) numbers. In the laboratory, L. raynerae sex ratios were also assessed over time but in the absence of predation pressure. Predation success and prey performance experiments evaluating differences between L. raynerae male, female, gravid female and copulating pairs exposed to notonectid predation were then examined. Under natural conditions, a female dominated copepod population developed over time and was correlated to predation pressure, while under predator‐free conditions non sex‐skewed prey population demographics persisted. Predator–prey laboratory trials showed no difference in vulnerability and escape performance for male, female and gravid female copepods, but pairs in copula were significantly more vulnerable to predation. This vulnerability was not shared by both sexes, with only female copepods ultimately escaping from successful predation on a mating pair. These results suggest that contact periods during copula may contribute to the development of sex‐skewed copepod ratios over time in ecosystems dominated by hexapod predators. This is discussed within the context of vertebrate and invertebrate predation and how these dissimilar types of predation are likely to have acted as selective pressures for copepod mating systems.     

Avian top predator and the landscape of fear: responses of mammalian mesopredators to risk imposed by the golden eagle

Top predators may induce extensive cascading effects on lower trophic levels, for example, through intraguild predation (IGP). The impacts of both mammalian and avian top predators on species of the same class have been extensively studied, but the effects of the latter upon mammalian mesopredators are not yet as well known. We examined the impact of the predation risk imposed by a large avian predator, the golden eagle (Aquila chrysaetos, L.), on its potential mammalian mesopredator prey, the red fox (Vulpes vulpes, L.), and the pine marten (Martes martes, L.). The study combined 23 years of countrywide data from nesting records of eagles and wildlife track counts of mesopredators in Finland, northern Europe. The predation risk of the golden eagle was modeled as a function of territory density, density of fledglings produced, and distance to nearest active eagle territory, with the expectation that a high predation risk would reduce the abundances of smaller sized pine martens in particular. Red foxes appeared not to suffer from eagle predation, being in fact most numerous close to eagle nests and in areas with more eagle territories. This is likely due to similar prey preferences of the two predators and the larger size of foxes enabling them to escape eagle predation risk. Somewhat contrary to our prediction, the abundance of pine martens increased from low to intermediate territory density and at close proximity to eagle nests, possibly because of similar habitat preferences of martens and eagles. We found a slightly decreasing trend of marten abundance at high territory density, which could indicate that the response in marten populations is dependent on eagle density. However, more research is needed to better establish whether mesopredators are intimidated or predated by golden eagles, and whether such effects could in turn cascade to lower trophic levels, benefitting herbivorous species.     

Uganda kob prefer high-visibility leks and territories

In lekking species, where males provide estrous females withlittle more than sperm, it has been widely supposed that theonly possible benefits to females of mate choice are genetic.We studied female choice of leks and territories in a reduncineantelope, the Uganda kob (Kobus kob thomasi), and found thatfemales consistently preferred high-visibility mating sites.Leks were elevated and had shorter grass and fewer thicketsthan the surrounding areas. Changes in the number of male andfemale kob on 10 leks were correlated with changes in surroundinggrass height, and both females and males preferred leks withexperimentally reduced grass height over neighboring controls.Within a lek, territory popularity was the primary determinantof male daily mating success, and females preferred territoriesrelatively far from thickets, but removal of thickets did notaffect female territory preferences. Because lion hunting successon kob increases with grass height and thicket density, femalesmay benefit directly from these preferences by reducing therisk of predation.     

Male–female evolutionary game on mate-locating behaviour and evolution of mating systems in insects

We present a model of a male–female evolutionary game on mate-locating behaviour. Two major mating systems are considered: "lek polygyny" (in which males aggregate to wait for females searching for males) and "searching polygyny" (in which males search for females emerging or waiting for males). The model predicts that lek polygyny is favoured (i) when male survivorship during lekking is sufficiently higher than that during mate searching, (ii) when female survivorship while visiting a lek is sufficiently higher than at the emergence site, or (iii) when searching efficiency is higher at a lek than at an emergence site. Furthermore, the model shows that a reduction in the reproductive value of females later in the day, which prevents males from performing riskier mate-locating behaviour, can result in a change of mating system. In addition, mixed mating systems can be realized as transient states during this shift.