Male Competition Research Articles

Condition- and context-dependent alternative reproductive tactic in Drosophila prolongata

Abstract Species with intense male–male competition for access to females often show alternative reproductive tactics (ARTs) where males of lower competitive ability adopt a sneaky behavior to gain access to mates. These ARTs are usually associated with intrasexual dimorphisms, in that males with distinct morphologies show different tactics. In some cases, however, males adopt different tactics without being dimorphic. Male Drosophila prolongata exhibit continuous variation in body size and shape, with enlarged forelegs that they use in male-male contests and in courtship, including stimulation of the female’s abdomen. During this “leg vibration,” however, nearby males can intercept the courted female and mate without their own courtship. Here, we studied the causes and consequences of these different mating tactics in competitive mating trials between males varying in their size and shape. We found that male mating tactics were condition-dependent. Whereas large, high-condition males were more likely to show leg vibration in their courtship, smaller, lower-condition males were more likely to intercept. However, the number of offspring produced was independent of male condition and reproductive tactic. We discuss possible scenarios for the evolution and maintenance of the ARTs and some future directions for the study of ARTs in this species and in general.

What do orange spots reveal about male (and female) guppies? A test using correlated responses to selection.

Female preferences for male ornamental traits can arise from indirect benefits, such as increased attractiveness or better viability of progeny, but empirical evidence for such benefits is inconsistent. Artificial selection offers a powerful way to investigate indirect effects of male ornaments. Here, we selected for the area of orange spots on male guppies, a trait subject to female preferences in our population, in replicated up‐ and down‐selected lines. We found a significant direct response to selection, and a correlated response in female preferences, with females from down‐selected lines showing less interest in more orange males. Nevertheless, up‐selected males sired more offspring in direct competition with low‐selected males, irrespective of female origin. We did not find a significantly correlated response to selection among any other fitness correlates we measured. Our results imply that female preferences for orange spots can lead to increased reproductive success of their sons, with no effect on general viability of progeny. Furthermore, although we demonstrate that female preferences may evolve via linkage disequilibrium with the preferred trait, the potential for runaway selection by positive feedback may be constrained by the lack of corresponding linkage with male reproductive competitiveness.

Maturational changes in song sparrow song

Age‐related changes in the production of sexually selected assessment signals have been identified across a diverse range of taxa, and in some cases, these changes have been shown to affect receiver response to those signals. One important type of change occurs even after a signaler reaches breeding age, a phenomenon known as delayed maturation. Delayed maturation has been observed in the songs of several bird species, with potential fitness consequences for males as a byproduct of female choosiness or male competition. Here, we analyzed songs recorded across the first three years of life in a cohort of hand‐reared song sparrows Melospiza melodia to detect early‐life age‐related changes in song. We focused on three measures of song complexity, including within song type variation, the average number of notes and the number of unique note types for the most common variant of each song type, and five measures of song production patterns, including singing rate, time interval between songs within a bout of the same song type, time interval between bouts (i.e. when the song type changes), within‐song stereotypy and between‐song consistency. All measures of song complexity and most measures of song production patterns (excluding within‐song stereotypy) changed significantly within individuals as birds aged from one to two years as well as from one to three years (excluding within‐bout time interval), whereas no significant changes occurred from two to three years of age. Based on these features, a linear discriminant model could distinguish between the song of young (age 1) and older (age 2 and 3) adult males, providing support that song could serve as an indicator of age in this species. We discuss potential implications of these results for mate choice and male–male competition in song sparrows.

Gender and competitiveness when earning for others: Experimental evidence and implications for sponsorship

AbstractResearch SummaryCareer paths depend not only on individuals' own competitiveness but also on the competitiveness of others in a position to advocate for them. In this article, we study competitiveness when rewards accrue to another individual. In particular, we ask how female and male managers' competitiveness changes when rewards from competition accrue to their female or male protégés, relative to when they accrue to themselves. Using an experimental approach, we find that when rewards accrue to protégés, male and female managers are equally competitive because female managers increase their competitiveness. However, male managers compete more for male rather than female protégés. This gap disappears when male managers know their protégés' risk preferences, suggesting a novel intervention to ensure equity in the sponsorship process.Managerial SummarySponsorship is key to individuals' career development and firms' human capital strategy. In this experimental study simulating an organizational setting, we investigate one aspect of sponsorship and ask whether managers' and protégés' genders affect managers' willingness to compete on behalf of their protégés. We find that when the rewards from competition accrue to protégés, female managers increase their competitiveness and eliminate the gender competitiveness gap present when rewards accrue to managers themselves. This suggests that, from a competitiveness standpoint, female and male managers are equally strong sponsors. However, male managers compete more for male, relative to female, protégés. This gap disappears when male managers have information about protégés' risks preferences, suggesting a novel approach that organizations can implement to reduce discrimination in sponsorship.

The context of sexual coercion in orang-utans: when do male and female mating interests collide?

Sexual coercion is widespread in the animal kingdom. Its direct forms, including harassment and forced copulation, have largely been investigated as an expression of (alternative) male reproductive strategies, rather than the result of a sexual conflict between the sexes. Likewise, the frequent occurrence of forced copulations in orang-utans (Pongo spp.) has been attributed to male strategies and more recently also to concealed female fecundity. So far, however, the immediate contextual variables leading to forced copulations have rarely been examined. We compared two orang-utan populations, Suaq (Pongo abelii, Sumatra) and Tuanan (Pongo pygmaeus, Borneo), both characterized by an individual-based fission–fusion lifestyle, whereas their socioecology differs. We assessed how the occurrence of female-resisted and voluntary copulations was affected by female reproductive state, male morph (unflanged or flanged), measures of male–male competition, male–female relationship and ecological factors. Besides female reproductive state and male morph, predictors of female resistance were related to male–male competition. First, female resistance was more likely towards subordinate males who were displaced from proximity to the female by another male during that association. Second, the presence of additional flanged males increased the probability of female resistance. Third, the latency to both the arrival of another male and to the end of the association after sexual interactions was shorter if there was female resistance. We conclude that sexual coercion in orang-utans is highly dependent on the vicinity of more dominant males and can only be understood in the light of sexual conflict: While males force copulations when at risk of losing access to a female and thus follow a ‘now-or-never’ strategy, female resistance follows a ‘not-you-now’ pattern, which is ultimately consistent with an infanticide avoidance strategy.

A new, “dwarfed” species of the phenacodontid “condylarth”Ectocionfrom the late Paleocene of Alberta, Canada, and its implications

A large collection of dentigerous jaws quarried from the Gao Mine locality, late Paleocene, Paskapoo Formation, central Alberta, Canada, documents a new species of the early Paleogene phenacodontid “condylarth” Ectocion Cope, 1882. The new species, Ectocion stockeyae, the smallest of the genus, occurs well before the abrupt global warming at the Paleocene–Eocene Thermal Maximum, an event purportedly causing the rapid evolution of “dwarfed” mammals, including a species of Ectocion; however, there is no evidence of increased temperatures at Gao Mine to account for the small size of Ectocion stockeyae, raising questions of the relationship between temperature and body size in Ectocion. Ectocion stockeyae also exhibits sexual dimorphism of the canines, a pattern in mammals often associated with a population structure in which the males are relatively few and polygynous, resulting in intense male rivalry for mating success. The sample of Ectocion stockeyae from Gao Mine includes a substantial majority of “juvenile” individuals retaining deciduous posterior premolars, many even after eruption of the molars had been completed, suggesting short life spans, accelerated growth, and rapid dental development in this species as expressed in Schultz’s Rule.

Mate-guarding duration is mainly influenced by the risk of sperm competition and not by female quality in a golden orb-weaver spider.

Males are expected to mate with as many females as possible, but can maximize their reproductive success through strategic mating decisions. For instance, males can increase their own fitness by mating with high quality females that produce more offspring. Additionally, males can adjust mating effort based on the relative distribution of females and male competitors. To test factors that influence male mate choice, we assessed male mating decisions in the golden silk orb-weaver spider, Trichonephila clavipes (Nephilidae), a species in which females are polyandrous, males guard females before and after copulation occurs and large males are the most successful at guarding mates. We tested the hypothesis that males spend more time guarding high quality females that are spatially isolated, and when the risk of sperm competition is higher. We also hypothesized that this effect increases with male body size. We assessed solitary and aggregated female webs in the field and quantified female quality (i.e., female body condition), male size (i.e., male body size), the risk of sperm competition (i.e., number of males in each female web), and mate-guarding duration (i.e., number of days each male spent in each web). We found that mate-guarding behaviour is largely influenced by the presence of male competitors. In addition, male body size seems to moderately influence male guarding decisions, with larger males guarding for a longer time. Finally, female body condition and type of web (i.e., solitary or aggregated) seem to play small roles in mate-guarding behaviour. As mate-guarding duration increased by 0.718 day per each additional male competitor in the web, and guarding behaviour prevents males from seeking additional mates, it seems that guarding females can be considerably costly. We conclude that failing to guard a sexual partner promotes high costs derived from sperm competition, and a male cannot recover his relative loss in fertilization success by seeking and fertilizing more females. In addition, the search for more sexual partners can be constrained by possible high costs imposed by weight loss and fights against other males, which may explain why the type of web only moderately influenced male mate choice. Following the same rationale, if high-quality females are not easy to find and/or mating with a high-quality female demands much effort, males may search females and guard them regardless of female quality. In conclusion, the factor that most influences male mate-guarding behaviour among T. clavipes in the field is the risk of sperm competition.

Mitochondrial superoxide dismutase overexpression and low oxygen conditioning hormesis improve the performance of irradiated sterile males

The Sterile Insect Technique (SIT) is a successful autocidal control method that uses ionizing radiation to sterilize insects. However, irradiation in normal atmospheric conditions can be damaging for males, because irradiation generates substantial biological oxidative stress that, combined with domestication and mass-rearing conditions, may reduce sterile male sexual competitiveness and quality. In this study, biological oxidative stress and antioxidant capacity were experimentally manipulated in Anastrepha suspensa using a combination of low-oxygen conditions and transgenic overexpression of mitochondrial superoxide dismutase (SOD2) to evaluate their role in the sexual behavior and quality of irradiated males. Our results showed that SOD2 overexpression enhances irradiated insect quality and improves male competitiveness in leks. However, the improvements in mating performance were modest, as normoxia-irradiated SOD2 males exhibited only a 22% improvement in mating success compared to normoxia-irradiated wild type males. Additionally, SOD2 overexpression did not synergistically improve the mating success of males irradiated in either hypoxia or severe hypoxia. Short-term hypoxic and severe-hypoxic conditioning hormesis, per se, increased antioxidant capacity and enhanced sexual competitiveness of irradiated males relative to non-irradiated males in leks. Our study provides valuable new information that antioxidant enzymes, particularly SOD2, have potential to improve the quality and lekking performance of sterile males used in SIT programs.

Mate guarding in primates arises due to partner scarcity, even if the father provides no paternal care at all

Paternal care is unusual among primates; in most species males compete with one another for the acquisition of mates and leave the raising of offspring to the mothers. Callitrichids defy this trend with both fathers and older siblings contributing to the care of offspring. We extend a two-strategy population model (paternal care versus male–male competition) to account for various mechanisms that could possibly explain why male callitrichids invest in paternal care over male–male competition, and compare results from callitrichid, chimpanzee and hunter-gatherer life history parameters. The survival benefit to offspring due to care is an insufficient explanation of callitrichid paternal care, and the additional inclusion of differences in lactation-related biology similarly do not change that picture. Instead, paternal care may arise in parallel with, or even as a result of, mate guarding, which in turn is only beneficial when partners are scarce as modelled by the birth sex ratio in callitrichids and menopause in hunter-gatherers. In that situation, care need not even provide any benefit to the young (in the form of a survival bonus) for guarding to out-compete multiple mating competition.

Density-dependent mating behaviors reduce male mating harassment in locusts

Male mating harassment may occur when females and males do not have the same mating objectives. Communal animals need to manage the costs of male mating harassment. Here, we demonstrate how desert locusts in dense populations reduce such conflicts through behaviors. In transient populations (of solitarious morphology but gregarious behavior), we found that nongravid females occupied separate sites far from males and were not mating, whereas males aggregated on open ground (leks), waiting for gravid females to enter the lekking sites. Once a male mounted a gravid female, no other males attacked the pair; mating pairs were thereby protected during the vulnerable time of oviposition. In comparison, solitarious locusts displayed a balanced sex ratio in low-density populations, and females mated irrespective of their ovarian state. Our results indicate that the mating behaviors of desert locusts are density dependent and that sex-biased behavioral group separation may minimize the costs of male mating harassment and competition.

Front Cover

EthologyVolume 127, Issue 11 p. i-i COVER IMAGE Front Cover First published: 04 October 2021 https://doi.org/10.1111/eth.13064AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Front Cover Male competition in Menochilus sexmaculatus. Volume127, Issue11November 2021Pages i-i RelatedInformation

Novel wing display and divergent agonistic behaviors of two incipient Psolodesmus damselflies.

Sexual selection via male competition is a strong evolutionary force that can drive rapid changes in competitive traits and subsequently lead to population divergence and speciation. Territorial males of many odonates are known to use their colorful wings as visual signals and to perform agonistic displays toward intruders. Psolodesmus mandarinus dorothea and Psolodesmus mandarinus mandarinus are two parapatrically distributed sister damselflies that share similar ecological characteristics but differ markedly in wing coloration. The wings of P. m. dorothea are mostly clear, whereas those of P. m. mandarinus have a large area of black pigmentation and a central white patch. We investigated whether territorial males of the two damselflies at breeding sites display distinct agonistic behaviors associated with their respective wing colors. Behavioral interactions between territorial and intruder males and their wing kinematics were filmed and analyzed for P. m. dorothea in Lienhuachih of central Taiwan, and P. m. mandarinus in Tianxiyuan andFusan of northern Taiwan. We observed that the P. m. mandarinus males exhibited a novel set of perched wing displays, which was not only absent in its sister P. m. dorothea but also previously unknown in Odonata. At breeding sites, perched rival males of P. m. mandarinus with pigmented wings exhibited escalating agonistic wing-flapping and wing-hitting displays toward each other. In contrast, territorial males of P. m. dorothea with clear wings engaged only in aerial chase or face-to-face hovering when intruder males approached from the air. These results indicate that the two sister P. mandarinus damselflies diverged behaviorally in territorial contests and support the hypothesis of coadaptation on the basis of wing colors and types of wing movement in Odonata. Our findings further suggest that divergent agonistic wing displays may play a pivotal role in the speciation mechanism of P. mandarinus damselflies. The sequential analyses of behavioral characteristics and progression suggest that P. m. mandarinus damselflies likely use mutual assessment of rivals in territorial contests.

Sexual dimorphism in an adaptive radiation: Does intersexual niche differentiation result in ecological character displacement?

Evolutionary radiations are one plausible explanation for the rich biodiversity on Earth. Adaptive radiations are the most studied form of evolutionary radiations, and ecological opportunity has been identified as one factor permitting them. Competition among individuals is supposedly highest in populations of conspecifics. Divergent modes of resource use might minimize trophic overlap, and thus intersexual competition, resulting in ecological character displacement between sexes. However, the role of intersexual differentiation in speciation processes is insufficiently studied. The few studies available suggest that intersexual niche differentiation exists in adaptive radiations, but their role within the radiation, and the extent of differentiation within the organism itself, remains largely unexplored. Here, we test the hypothesis that multiple morphological structures are affected by intersexual niche differentiation in “roundfin” Telmatherina, the first case where intersexual niche differentiation was demonstrated in an adaptive fish radiation. We show that sexes of two of the three morphospecies differ in several structural components of the head, all of these are likely adaptive. Sexual dimorphism is linked to the respective morphospecies‐specific ecology and affects several axes of variation. Trait variation translates into different feeding modes, processing types, and habitat usages that add to interspecific variation in all three morphospecies. Intrasexual selection, that is, male–male competition, may contribute to variation in some of the traits, but appears unlikely in internal structures, which are invisible to other individuals. We conclude that intersexual variation adds to the adaptive diversity of roundfins and might play a key role in minimizing intersexual competition in emerging radiations.

Determinant Factors for Throwing in Competition in Male Elite Handball

The aims of this study were to define determinant factors that affected throwing actions used to score goals in handball, and to study the effectiveness of throwing actions and their relationships with different factors during their use, such as: the throwing distance, type of arm build, type of throw, whether it is done while jumping or while supported, the last supporting foot and the previous step cycle, as well as their relationship with the final score of the game in elite male handball competitions. A total of 1049 shots from 24 matches in the 2018/19/20 International Men’s Handball Championship were analysed. The results show that distance is relevant in the effectiveness of throwing, setting the build up, throwing while supported or jumping, the type of throwing, the type of steps cycle used and the supporting foot. This seems to indicate that the determining factor that affects a throw is distance.

Energetic Lifestyle Drives Size and Shape of Avian Erythrocytes.

The size and shape of red blood cells (erythrocytes) is determined by key life history strategies in vertebrates. They have a fundamental role to deliver oxygen to tissues, and their ability to do so is shaped by the tissue's need and their shape. Despite considerable interest in how other components of blood are shaped by ecology and life history, few studies have considered erythrocytes themselves. We tested how erythrocyte size and shape varied in relation to energetically demanding activities using a dataset of 631 bird species. We found that in general, birds undergoing greater activities such as long distance migration had smaller and more elongated cells, while those with greater male-male competition had smaller and rounder cells. Smaller, more elongated erythrocytes allow more rapid oxygenation/deoxygenation and support greater aerobic activity. The rounder erythrocytes found in species with strong male–male competition may stem from younger erythrocytes deriving from androgen-induced erythropoiesis rates. Finally, diving species of bird had larger erythrocytes, indicating that erythrocytes are acting as a vital oxygen store. In summary, erythrocyte size and shape in birds are driven by the need to deliver oxygen during energetically costly activities.

Territoriality is just an option: allocation of a resource fundamental to the resource defense polygyny in the European wool carder bee, Anthidium manicatum (Hymenoptera: Megachilidae)

The wool carder bee Anthidium manicatum is one textbook example of resource defense polygyny among solitary bees, known for intense male–male competition, forced copulations, and the extreme form of interspecific territoriality toward other flower visitors. This mating system depends on the spatial structure of the defended resource and requires several adaptations in males. The allocation of patches with host plants as well as male body size and phenology was analyzed over 3 years in the diverse habitat of a botanical garden. Anthidium manicatum males searched in groups up to 12 individuals a wide diversity of patches with various food plants of foraging females. Territories were established in small high-quality patches only. Males abandoned aggressive and territorial behavior in large patches. Available patches were occupied by males of the various body size fractions independently of each other according to patch profitability. The higher competitive weight of large males in small patches compared to spacious ones was balanced by an opposing correlation of patch profitability. Although the mating system in A. manicatum is clearly a resource defense polygyny, males were found to be plastic in their behavior, and territoriality was not consistently observed. Mate acquiring tactics, be they territory holder (bourgeois), sneaker, floater, or scrambler for mating, can be considered to be different behavioral phenotypes within one environmentally sensitive conditional strategy.Significance statementTerritoriality is a rare and derived pattern in solitary bee mating behavior. In most cases of territoriality, males defend rendezvous places to meet freshly emerged, virgin females. While this type of mating behavior fits still into the framework of ancestral monandry of aculeate Hymenoptera, the continually polyandric resource defense polygyny found in the genus Anthidium is highly derived. Males occupy flower resources exploited for larval provisions and extort copulations from provisioning nesting females. Territoriality in Anthidium does not lead to a monopolization of females, the exclusion of many competitors from reproduction, and a reduction of sperm competition as is typical for resource-based mating systems. Contrary, Anthidium is a highly promiscuous species and both males and females are lifelong engaged in copulations with multiple mates. Also, the allocation of the resource fundamental to the defense polygyny was found to be more fairly balanced than expected. This study diversifies the mating system of anthidiine bees and demonstrates unusually high plasticity in the resource allocation of a territorial species.

Patterns of Visual and Ultraviolet Reflectance in Femoral Gland Secretions of Two Desert Lizards

Femoral gland secretions in lizards convey chemical information about the health and social status of the depositing individual. These secretions influence behaviors related to female mate choice and male–male competition, but little is known about how they are first located by lizards in the environment. Secretions are visually conspicuous and can be sighted from a distance by visually adept lizards, but the specificity of secretion reflectance to the depositing species remains unknown. We examined the reflectance spectra of femoral gland secretions from two sympatric lizard species, Aspidoscelis tigris and Gambelia wislizenii, to determine whether secretions could be visually distinguished. Mean reflectance did not differ between species, but A. tigris had higher reflectance in ultraviolet wavelengths. For both species, lizards in better body condition, as determined by the residuals of the relationship between snout–vent length and body mass, had higher ultraviolet reflectance. In summary, our results indicate that femoral gland secretions can be visually discriminated between species if the discriminating lizard is ultraviolet sensitive.

Weight Loss Strategies in Male Competitors of Combat Sport Disciplines.

Background and objective: The use of suboptimal weight loss strategies in order to reach specific weight ranges as observed in combat sport disciplines can give rise to severe health problems. However, particular aspects regarding management of weight category comparing three sport disciplines remain to be investigated. Therefore, the aim of the present study was to obtain information regarding the weight loss strategies that competitors performed before a tournament. Materials and Methods: This article describes the most common dietary-nutritional strategies used by 140 national university male competitors of judo (n = 52), karate (n = 40) and taekwondo (n = 48) in order to achieve a specific weight, according to the rapid weight loss questionnaire (RWLQ) and the EAT-27 questionnaire. Results: Around 50% of participants were not involved in a weight loss process. Among the remaining participants, we considered three periods for weight reduction: less than 1 week (35% in judo, 8% in karate and 19% in taekwondo), less than 1 month (17% in judo, 15% in karate and 26% in taekwondo) and more than 1 month (0% in judo, 5% in karate and 21% in taekwondo). Severe fasting, focused on food/water restriction, was the most commonly used strategy, being more frequent in judo players. Light weight judo practitioners generally lost 2–5 kg before the contest. One third of participants avoided carbohydrate consumption when performing food restriction. Finally, individuals that reduced weight in the last week seemed to develop an unhealthy psychological relationship with food. Conclusion: All these aspects could be particularly relevant, providing information regarding how competitors manage basic nutritional concepts that guide dieting strategies. This information is relevant to prepare future educational interventions in the area of nutrition for competitors, coaches and technical staff.

Winner and loser effects influence subsequent mating interactions in crayfish

In species whose social structure includes dominance relationships, individuals are likely to engage in frequent agonistic interactions with conspecifics, and these interactions can have substantial effects on participants. For example, ‘winner’ and ‘loser’ effects, whereby winning or losing a contest increases the probability of winning or losing subsequent encounters, have been described in many species. However, a smaller body of research has shown that winning or losing a contest can lead to additional behavioral changes that affect other domains of an individual’s social experiences. Here, we report on an experiment designed to evaluate the effects of prior contests on subsequent mating interactions in the crayfish (Faxonius virilis). We presented males with mating opportunities either immediately following or 7 days after a contest with a conspecific male. We predicted that winners would be more likely to mate than losers, because of either or both winner/loser effects and differences in male competitiveness. We found that, when presented with a mating opportunity immediately following a contest, winning males were more likely to mate than were losing males. We also found that these differences had eroded within 7 days, such that there was no significant difference in the proportions of winners and losers that mated after that period. We concluded that the changes in mating behavior that we observed immediately after a contest were likely due to relatively short-term winner and loser effects, rather than any differences in the males’ competitiveness, which would presumably be of longer duration.

On the evolution of male competitiveness

Since a man’s reproductive success depends on his ability to outcompete other men, male competitiveness may be expected to have been exposed to strong selective pressure throughout human history. Accordingly, the relatively low level of physical violence observed between men has been viewed as a puzzle. What could have limited the eagerness of men to out-compete each other? I study the evolution of male competitiveness in a model where men compete for both reproductive and productive resources. I show that high levels of male competitiveness are then consistent with evolution by natural selection if (a) the ecology is generous enough for men to supply little or no food to their children, (b) competing is not too costly in terms of productive resources, and (c) relatedness among males is low enough. While the main analysis takes women to passively accept the husband that emerges from the male-male competition, the results are qualitatively robust to allowing for female mate choice following the male-male competition game. Possible implications for our understanding of the evolution of marriage systems are discussed.