Male Fighting Research Articles

Uganda kob mating success does not increase on larger leks

One explanation for the movement of sexually receptive females to clusters of male territories in lek-breeding species is that larger clusters provide females with higher-quality mating partners, as would be the case if males were distributed between leks in an ideal free distribution for unequal competitors. This ideal free model of lek evolution predicts that male competitive ability and mating success will be greater on larger leks than smaller ones. I tested these predictions by comparing the mean number of males on 19 different Uganda kob leks with the sex ratio, the availability of oestrous females, mating rates, male fighting rates and male turnover rates. Contrary to the predictions of the model, numbers of females, receptive females and fights increased proportionally with lek size, but were no greater per male on larger leks. Multivariate analyses of male and female numbers on leks showed that male numbers were associated with female numbers, female numbers in the past, and a variety of habitat variables which may have related to the costs of holding a lek territory, but female numbers varied only with male numbers and female density in the area. These data do not provide evidence that females gain access to superior males by mating on larger leks, though they do support the possibility that lekking may be promoted by a tendency for larger leks to retain females longer.

Competitive and territorial fighting: Two types of offense in the rat

Two types of fighting (offense) were compared and contrasted in three experiments on the laboratory rat. In Experiment 1, competitive fighting was obtained in pairs of hungry cagemates by placing one food pellet into their food hopper. In Experiment 2, territorial fighting was obtained by introducing an unfamiliar intruder into the home cage of a male and female pair. Both types of fighting had the same motor patterns. Whereas territorial fighting is strongest against intruders of the same sex, competitive fighting is stronger against the smaller opponent (in this case female) regardless of the sex of the test animal. Whereas territorial fighting is stronger in males, competitive fighting is stronger in females. Whereas gonadectomy reduces territorial fighting in males but not females, it reduces competitive fighting in both sexes. In experiment three, it was shown that food deprivation increases competitive fighting, while it reduces territorial fighting. On the basis of these findings a revised model of the organization of the offense motivational system is proposed.

Behavior of ergatoid males in the ant,Cardiocondyla nuda

Ergatoid males of the ant,Cardiocondyla nuda, attack and frequently kill young males during or shortly after eclosion. Smaller colonies therefore contain typically only one adult male, which may inseminate all alate queens which are reared in the colony over a few weeks. In larger colonies, several males may be present, however, fighting among adult males was not observed. We discuss the significance of male fighting behavior in ants.

Context and consequences of comb displays by male rock ptarmigan

Abstract. Male rock ptarmigan, Lagopus mutus, display their supraorbital combs for about 50% of the time during both inter- and intra-sexual interactions in the breeding season, but rarely when they are alone. During three seasons in the Canadian high arctic, mating success of male rock ptarmigan was positively correlated with both comb condition and previous breeding experience. There was no general relationship between a male's comb size and his mating success, contrary to results obtained in both a previous study in this same population and experimental studies on other species with combs. There was, however, a correlation between comb size and mating success among inexperienced males that may explain the results from other studies. Model presentation experiments also revealed significant relationships between comb condition, comb size and aggressiveness, such that males with smaller combs or combs in poor condition were less likely to attack male models with artificial combs. The size of model combs, however, had no influence on male aggressiveness. Because combs are frequently attacked during male × male interactions, the condition of these ornaments may honestly advertise male fighting ability and as a result may be an important criterion for female choice.

Inclusive fitness in a homogeneous environment

A general formulation of inclusive fitness is proposed which specifically accounts for competitive effects between relatives. As an example, for an asexual population in a homogeneous inelastic environment, such as is found in a stepping-stone model of dispersal, the inclusive fitness of a breeding female, under weak selection, is independent of her direct effect on the fitness of other individuals in the population. More precisely, suppose a female acts in a way that changes not only her own fitness but the fitness of several other females in the population who may be relatives (i.e. she changes the number of their offspring). I call these changes the direct effects of the action. There will also be indirect effects on the fitness of these and other females which come from the competitive impact of the extra offspring in the next generation. The principal result is that these indirect effects exactly cancel all the direct effects except the direct effect of the actor on herself.

Patterns of fluctuating asymmetry in weapons: evidence for reliable signalling of quality in beetle horns and bird spurs

Fluctuating asymmetry is an epigenetic measure of the ability of individuals to undergo identical development of a usually bilaterally symmetrical character on both sides of the body. Horns of beetles and spurs of birds are elaborate structures usually restricted to or enlarged in individuals of the limited sex and frequently used in intrasexual combat. Individuals with large horns usually win fights against individuals with small horns which suggests that horn size may reliably signal male fighting ability. A comparative study of the patterns of fluctuating asymmetry in horns of beetles and spurs of birds showed that the degree of asymmetry in these secondary sex traits was considerably larger than in elytra and wing length, which are apparently not subjected to sexual selection. There was a negative relationship between the degree of asymmetry and size of the secondary sex trait while the relationship for elytra and wing length was flat or U-shaped. This demonstrates that horn and spur size may reliably reflect male quality as determined by the degree of fluctuating asymmetry.

Causes of assortative mating in arthropods

Assortative mating by size, one of the most common mating patterns in natural populations, may be explained by three hypotheses: (1) mate choice, whereby large males, large females or large individuals of both sexes choose large mates because they benefit reproductively and are differentially capable of exercising choice; (2) mate availability, whereby large females or large individuals of both sexes are differentially available for mating because of size-differential variation in mating probability or timing that is unrelated to mate choice; and (3) mating constraints, whereby relative size differences between males and females cause physical or energetic difficulties with courtship, pairing or mating. Analysis of the causes of assortative mating in well-studied arthropod species provides some support for each hypothesis in one or more species. However, comparative analysis of many species indicates that assortative mating is most closely associated with the pattern of large size of paired males and females relative to unpaired males and females and the occurrence of long pairing durations and male fighting. These comparative data therefore implicate two hypotheses for the causes of assortative mating in most arthropods: male choice of large females combined with male-male competition, and increased availability of large females combined with male-male competition. The female availability hypothesis may be more plausible because male choice and male-male competition are apparently antagonistic processes whose effects usually do not coincide. Distinguishing between hypotheses based on mate choice, mate availability and mating constraints is crucial to understanding the roles of natural selection and sexual selection in causing assortative mating.

Sexual Selection and Assortative Mating in Subdivided Populations of the Thrips Elaphrothrips tuberculatus (Insecta: Thysanoptera)

AbstractThis study presents four years of data on size‐related mating patterns in Elaphrothrips tuberculatus, a subsocial thrips inhabiting subdivided populations (clusters of hanging dead oak leaves) that vary in sex ratio, operational sex ratio (ratio of males to females guarding eggs), and number of adults. Laboratory observations, experimental removals of guarding males, and field collections showed that: (1) males guard mates after copulation, (2) guarding males are larger than non‐guarding males, and (3) large male mating advantage is caused by male fighting. The populationwide intensity of sexual selection for large male body size varied substantially among years, reflecting yearly differences in the sex ratio and operational sex ratio. Among local populations (leaf clusters), the sexual selection intensity was correlated with the operational sex ratio in each year, and with the sex ratio in three of four years. Males and females mated assortively for size (fore‐femora length) in 1986, but not in 1983, 1984, or 1985. Assortative mating in 1986 was attributed to Darwin's (1871) mechanism for sexual selection in monogamous species: in this year alone, there was a highly significant tendency for large females to initiate breeding earlier than smaller females and strong directional selection for large male body size. Population subdivision affects mating patterns of E. tuberculatus by: (1) creating single‐male populations where male size does not affect mating success, (2) promoting high sexual selection intensities, relative to a continuous population, when the population‐wide sex ratio is female biased, and (3) constraining the size covariation between paired males and females.

Female Mating Behaviour and Multiple Matings in the Fly, Dryomyza Anilis

Multiple matings by females of the fly, Dryomyza anilis, were studied at small carcasses where they arrived to lay their eggs. Males of the species are territorial and fight over females and their oviposition sites. Arriving females were quickly captured by males and male fights over females as well as take-overs were common. The average number of matings per female was 2.8 and the average time a female spent at the carcass was 1 h 49 min (from arrival to the end of oviposition). The total mating time was almost twice as long in females which mated over five times than in females which had only one mating. The increase in mating time with increasing number of mating was totally due to the increase in time spent in copulation bouts (the species copulates and oviposits in several bouts). In attacks by lone males resulting in the separation of a pair, the attacker continued with the female in only one half of the cases (take-overs). In the other half a third male captured the female after she had escaped from the struggling males. In successful take-overs the new mate was usually larger than the earlier mate whereas in the other cases the new mate was almost always smaller than the earlier mate. Female resistance during matings was common and the various conflict behaviours are described. Female resistance became stronger in consecutive matings and within the same mating females resisted earlier in the second copulation bout than in the first one. In addition, larger females resisted more per mating, spent less time in copulation bouts per mating and had fewer matings than small females. Some possible costs and benefits of multiple matings were studied. Owing to male mating behaviour, where females are taken away from the carcass, females may loose feeding opportunities which can reduce their egg production. Male mating behaviour also delays female oviposition which can put the larvae in a worse position in food competition with other earlier larvae. Females arriving at carcasses to lay eggs face a situation where they can benefit from male guarding during oviposition but male fighting and take-overs can result in a long chain of matings which is disadvantageous for them.

Adaptation, compromise, and constraint: the development, morphometrics, and behavioral basis of a fighter-flier polymorphism in male Hoplothrips karnyi (Insecta: Thysanoptera)

Males of the colonial, wing-polymorphic thrips Hoplothrips karnyi (Hood) fight each other with their forelegs in defense of communal female oviposition areas. In this study, males were reared individually under varying conditions of food deprivation to investigate the developmental cues used in morph determination and the relationships between wing morph, developmental time in each instar, propupal weight, and five adult morphological characters associated with fighting ability and dispersal ability. Males deprived of food for five days midway through the second (final) larval instar had smaller propupal weights and were more likely to develop wings than males deprived of food in the first instar or control males. However, the mean propupal weight of all males that developed wings was not significantly less than that of wingless males. Wing morph of female parents had no measurable effect on this character in the offspring. Wingless males possess relatively larger fore-femora and prothoraces than do winged males, but winged males possess relatively larger pterothoraces (Fig. 1). Behavioral observations of wingless and winged males of similar weight as propupae showed that wingless males won fights and became dominant in oviposition areas. Thus, a trade-off exists between characters associated with male fighting and dispersal ability. The cost of wings, in terms of fore-femora size and prothorax size, increased with propupal weight. Wingless males that developed in the experimental treatment that produced a high proportion of winged males were relatively small in size, and were intermediate in body shape with respect to winged males and other wingless males (Fig. 2). This shape intermediacy indicates that there may be developmental constraints on alternative tactics of resource allocation. Total developmental time varied between wing morphs, but was not correlated with propupal weight or adult morphological characters of winged or wingless males. For wingless males that developed in the treatment that produced a high proportion of winged males, adult morphological characters were negatively correlated with the duration of the second instar. This correlation suggests that the development of small wingless males involves a compromise between the benefits of large adult size and the costs of prolonging the second instar to increase the probability of becoming larger.

Risks and benefits of lethal male fighting in the colonial, polygynous thrips Hoplothrips karnyi (Insecta: Thysanoptera)

Males of Hoplothrips karnyi (Hood) (Insecta: Thysanoptera), a colonial fungus-feeding thrips, fight each other in defense of communal egg mass sites, where they mate with females that come to oviposit. Fighting males stab each other with their enlarged, armed forelegs and hit each other with their abdomens. Escalated fights occur between large males of similar size. Fights are often lethal; males that died during observations fought more frequently than other males, were stabbed more often and more severely than other males, and were relatively large, but somewhat smaller than their opponents. Large males tend to win fights and guard egg masses, and they secure about 80% of last matings before ovipositions. Guarding males apparently assess female reproductive condition by putting their forelegs partially around females' abdomens; guarding males, but not nonguarding males, mate preferentially with females that have yet to oviposit. Non-guarding males mate with females away from egg masses, sneak matings at egg masses, and occasionally challenge guarding males. Challenges tend to follow matings by non-guarding males at egg masses. Each of four observed or inferred takeovers was followed by the death of the guarding male that lost. Male fighting strategies are discussed in terms of the consistency of lethal fighting with game theory models. Guardin males appear to pursue a classical “hawk” strategy of “escalate until injured or victorious”. This strategy may be advantageous because only large males become guarders, the mating success of guarders greatly exceeds that of non-guarders, and high population viscosity ensures that benefits from killing an opponent accrue directly to gaurders. The occurrence of challenges by large non-guarders implies that fighting ability and resource value asymmetries between males change over time; such changes may result from the energetic costs of guarding, injury to guarding males, or depletion of guarding males' supply of sperm.

Alternative Male Mating Tactics in a Thrips: Effects of Sex Ratio Variation and Body Size

Field observations show that males of Elaphrothrips tuberculatus (Thysanoptera: Phlaeothripidae), a subsocial thrips that inhabits clusters of hanging dead oak leaves, engage in either of two mating tactics, fighting or sneaking that are associated with their body size. Large males fight and guard individual egg-defending females, relatively large nonguarding males fight and challenge guarding males, and relatively small nonguarding males attempt to mate with females while avoiding guarding males. Field collections conducted during 4 years showed that: (1) nonguarding males on the same leaf as guarding males and females (same-leaf' nonguarding males) were significantly smaller than nonguarding males on different leaves (different-leaf nonguarding males) in 3 of 4 years; (2) among years, the size difference between same-leaf and different-leaf nonguarding males was positively correlated with the sex ratio (percent males); and (3) within years, local populations in which at least one of the nonguarding males was a same-leaf male exhibited significantly higher sex ratios. By inference from the observation data, same-leaf males were regarded as sneaks, different-leaf males were temporarily unsuccessful fighters, and male choice of mating tactics depended upon their size and the local sex ratio. Both small body size and a high local sex ratio may be viewed as correlates of a male's inability to secure a female on eggs by searching or fighting. Alternative hypotheses for the data linking male size, location and sex ratio are discussed; relatively small nonguarding males may be intrinsically better at sneaking, or large nonguarding males may fight rather than sneak because of a strong selective association between prior guarding success and aggressiveness. In E. tuberculatus, male mating tactics may be classified as a condition-dependent, reversible strategy, for which the fitness returns of the two tactics are unequal; males sneak when they have an especially low probability of success at winning fights and guarding females.

Testosterone and cortisol responses to competitive fighting in human males: A pilot study

Departamento de Psicologia Fisiologica (A.S., V.S., F.S.) and Laboratorio de MedicinaNuclear e Isotopos (L.L.), Hospital Clinico Universitario, Universitat de Valencia, Valencia,SpainSerum testosterone and cortisol levels were measured by radioimmunoassay in 14young male judo competitors, in samples taken 10 minutes before and 45 minutes aftertwo different pr(Redures. The first involved physical exercise and the second competi-tive fighting. Both procedures were of 5 minutes duration and sessions took plate atthe same time (between 10:00 \.M. and 12:00 P.M. liR-al lime) but on different days.Comparing the two situations over all subjects revealed that testosterone increasedafter exercise and decreased slightly after competition. Between subject comparisonssuggested that contrary to previous claims, winning or losing did not significantlychange the testosterone and cortisol levels. Comparisons of subjects who were membersof the Regional Team with individuals who were not part of thai gronp confirmed thatmemhers increased their testosterone levels after competition, whereas the nonniem-bers showed a significant decrease. Moreover, success of the individuals, in theirsporting record, correlated positively and significantly with the changes of testosteroneohserved during the competition. These preliminary results suggest that previouspersonal experience of success can infiuence the pattern of the psychoend(KTine re-sponse to a contest situation.Key words: physical exercise, judo competition, victory, defeatINTRODUCTIONPhysiological responses to the experiences oi victory and defeat include the modi-fication of circulating levels of some hormones. Clinically, sporting competitions havebeen seen as suitable situations to study hormonal responses to winning and losing.Mazur and Lamb 11980] found that the pattern in changes of testosterone was differentin winners and losers of a tennis match. Winners generally showed increases andlosers decreases in titers of this steroid and significant differences were evident I to2 hours after the match. Hlias [1981] found that subjects winning a wrestling matchshowed significantly greater increases than losers when he compared percentagechanges between testosterone levels seen 10 minutes before and 10 minutes after thematch. Winners also showed significantly greater increases in cortisol than losers.

Territoriality and fighting in a colonial thrips, Hoplothrips pedicularius, and sexual dimorphism in Thysanoptera

ABSTRACT. Hoplothrips pedicularius (Haliday) (Thysanoptera: Phlaeothripidae), a tubuliferan thrips in which males possess greatly enlarged forelegs, lives in colonies on Stereum fungus. Females oviposit onto communal egg masses, and males fight by grasping and stabbing with their forelegs in territorial defence of oviposition areas. Prolonged escalated fights occur between males who are of similar size. Larger males usually win fights and become dominant at the oviposition area. Dominant males secure 80% of matings, and mate most frequently during oviposition periods, with an ovipositing female. Smaller, subordinate males avoid fights and attempt to 'sneak’copulations. However, they occasionally challenge the dominant male. Challenges tend to follow copulations by the subordinate male and occur more frequently between males who are of similar size. Subordinate males who eventually leave the oviposition area are larger than those who remain, have frequently challenged the dominant male, and have more frequently been stabbed. Sexual dimorphism in thrips is associated with gregariousness, claustral habitats, female‐biased sex ratios, and male winglessness. In thrips genera in which males exhibit foreleg armature, males are larger relative to females. The ecological circumstances promoting sexual dimorphism and male fighting in spatially‐structured populations are discussed.

Prior-residence effect in Betta splendens..

Male Siamese fighting fish were presented with the visual image of an aggressive male conspecific for a 150-min test, with attack behaviors monitored continually. A 10-day period of residency in either the test tank or its exact replica resulted in more persistent attack than 10 min of residency. Testing in water other than that in which subjects had resided for 10 days did not produce a reduction in attack. Finally, the extent of attack behavior occurring early in testing was highly and positively correlated with subsequent attack duration; that is, at the start of an encounter, and before severe physical damage has been caused, Bettas may communicate to opponents their "intention" to engage in persistent, injurious aggression.

Serum cortisol, testosterone, and testosterone-binding globulin responses to competitive fighting in human males

Levels of circulating cortisol, testosterone, and testosterone-binding globulin were measured in 15 male wrestlers in relation to wrestling bouts and their outcomes. Concentrations of cortisol and testosterone increased consistently during wrestling bouts, while levels of testosterone-binding globulin dropped. Winners of competive matches showed greater increases in both cortisol and testosterone than losers. These findings indicate that humans, like other social mammals, may undergo specific endocrine changes in response to victory or defeat.

Pentobarbital sodium and attack behavior in male Siamese fighting fish.

An experiment was undertaken to determine the effects of pentobarbital sodium on intraspecific attack behavior in male Siamese fighting fish in an attempt to extend earlier findings with chlordiazepoxide and secobarbital sodium. Pairs of fish fought while immersed in 20 microgram/ml or 40 microgram/ml pentobarbital sodium or plain water. The 40 microgram/ml group showed significantly less attack (e.g., biting, jaw locking) than either control or low dose groups without producing a change in general arousal. Quasisexual behavior, seen in an earlier chlordiazepoxide study, did not occur in the present study.

An attempt to separate the roles of corticosterone and ACTH in the control of post-shock fighting behaviour in male laboratory mice

One experiment was conducted to separate the roles of corticosterone and ACTH in the mediation of the facilitatory effects of experiencing shock on subsequent fighting behaviour in male mice. It was found that (1) treatment with electric foot-shock and single injections of ACTH (one dose level) lead to comparable increases in subsequent fighting in intact males; (2) preventing changes in testosterone secretion by combined castration and testosterone replacement does not occlude or modify the facilitatory effects of shock or ACTH on subsequent fighting; and (3) preventing changes in both testosterone and corticosterone secretion by combined castration—adrenalectomy and testosterone—corticosterone replacement prevents shock and ACTH induced increases in fighting. These findings suggest that corticosterone plays a more important role than ACTH in the mediation of the facilitatory effects of shock on subsequent fighting behaviour in male mice.

Role of corticosterone in the control of post-shock fighting behaviour in male laboratory mice

Two experiments were conducted to examine the role of corticosterone in controlling fighting subsequent to electric foot-shock in male mice. It was found that (1) treatment with corticosterone restores post-shock fighting in adrenalectomized males but not in castrated-adrenalectomized males; (2) raising cortieosterone levels induces post-shock fighting in castrated-adrenalectomized males treated with testosterone but not in castrated-adrenalectomized controls treated with a placebo; and (3) preventing corticosterone responses to shock occludes the increasing in fighting which normally follow shock in intact males. These findings suggest that (1) corticosterone plays an important role in the control of post-shock fighting in mice; (2) this importance of corticosterone is dependent on the presence of circulating testosterone, or other androgens; and (3) corticosterone responses to the experience of shock may be involved in the mediation of the facilitatory effects of this experience on subsequent fighting behaviour.

Temporal relationships between shock treatment and intermale fighting behaviour in laboratory mice. Effects of modifying testicular and adrenal functions

The three experiments of this series were conducted to (1) examine subsequent effects of electric shock on intermale fighting in previously isolated mice, and (2) determine to what extent post-shock fighting is affected by manipulations of the pituitary-gonadal and pituitary-adrenocortical axes. In experiment 1 it was found that shock treatment significantly increases fighting 1 2 to 1 h later. Experiment 2 showed that castration alone does not affect post-shock fighting, whereas adrenalectomy and castration combined with adrenalectomy both inhibit such fighting. Experiment 3 showed that pretreatment with testosterone increases fighting in intact males, but fails to restore post-shock fighting in adrenalectomized and castrated-adrenalectomized males. These findings suggest that (1) the pituitary-adrenocortical axis plays an important role in controlling post-shock fighting in mice, and (2) the inhibition of post-shock fighting by adrenalectomy and castration combined with adrenalectomy is not a result of the loss of adrenal testosterone which accompanies these operations.