Male-male Aggressive Interactions Research Articles

Angry caciques: intrasexual aggression in a Neotropical colonial blackbird

Intraspecific aggressive behavior usually mediates competition for breeding and non-breeding resources among females and for mating opportunities among males. Variation in intrasexual aggressive levels across social and breeding contexts might then differ between sexes or converge due to different reasons. We studied three colonies of the polygynous Red-rumped cacique (Cacicus haemorrhous) during one breeding season. We evaluated whether the frequency of female-female and male-male aggressive interactions (number of interactions corrected by total number of individuals of the focal sex) varied with social context (total number of individuals of each sex in the colony) and breeding stage (number of nests under construction and nests with offspring) at each colony. We also tested for the occurrence (linearity and steepness) of a dominance hierarchy among banded males in one colony. We predicted positive correlations between female-female aggression and nests under construction (i.e. competition for nest sites) and between male-male aggression and nests under construction (a proxy for fertile females) and also male-male aggression and number of males (i.e. disputes for dominance rank) in the colony. We observed 533 female-female and 608 male-male aggressive interactions. Female-female aggressive interactions increased with the number of nests under construction in the colony, and decreased during incubation and nestling stages. Male-male aggressive interactions increased with the number of nests under construction, but not with the number of males in the colony. However, we found a steep and linear dominance hierarchy among males shaped by aggressive interactions. Our results suggest that (i) females behave aggressively when competing during the nest-building stage, probably for nest sites and materials; and (ii) male aggression determines the dominance hierarchy and is related to mating opportunities.HIGHLIGHTS● We observed intrasexual aggressive interactions across breeding stages in a blackbird with female-only parental care.● Female-female and male-male aggressive interactions increased when nests were under construction in the colony.● Dominance hierarchy was evaluated for males and it was linear and steep.● Results suggest females compete for nest sites and male aggression shapes dominance and is associated with mating opportunities.

Agonistic character displacement of genetically based male colour patterns across darters.

Agonistic character displacement (ACD) occurs when selection to avoid maladaptive interspecific aggression leads to the evolution of agonistic signals and/or associated behavioural biases in sympatry. Here, we test for a pattern consistent with ACD in male colour pattern in darters (Percidae: Etheostoma). Male colour pattern has been shown to function in male-male competition rather than female mating preferences in several darter species. Additionally, males bias their aggression towards conspecific over heterospecific males in sympatry but not in allopatry, consistent with divergent ACD in male behavioural biases. We use a common garden approach to show that differences in male colour pattern among four closely related darter species are genetically based. Additionally, we demonstrate that some aspects of male colour pattern exhibit enhanced differences in sympatric compared to allopatric populations of two darter species, consistent with ACD. However, other male colour traits are more similar between species in sympatry compared with allopatry, indicating that not all signal components are under strong divergent selection in sympatry. This study provides evidence that interspecific male-male aggressive interactions alone can promote elaborate male signal evolution both between and within species. We discuss the implications this has for male-driven ACD and cascade ACD.

Can estrogens be considered as key elements of the challenge hypothesis? The case of intrasexual aggression in a cichlid fish.

Territorial aggression has been widely studied in males and it has been historically suggested that androgens are key mediators of this behavior. However, more recent evidence suggests that it is the aromatization to estrogens, rather than androgens themselves, that is key to regulating this behavior. Females also display aggressive behaviors, but the physiological regulation of female aggression is still understudied when compared to males. In this context, the challenge hypothesis postulates that male-male aggressive interactions stimulate the production of androgens in males in periods of social instability. Here we determine plasma sex steroid levels in Cichlasoma dimerus to assess whether estrogens are related to aggressive behavior and to test the challenge hypothesis in both males and females. We set-up challenge trials as intrasexual dyadic encounters and determined androgen and estrogen levels before and after the trial in both winners and losers. Even though there were no differences in initial estradiol-17β plasma levels between male winners and losers, initial levels were higher (p = .046) in female winners than in losers, while there were no differences in testosterone or 11-ketotestosterone levels. After trials, both males and females showed elevated levels of estradiol-17β and both androgens, but only males exhibited a significant 1.45, 5.42 and 3.2-fold increase in estradiol-17β, testosterone and 11-ketotestosterone, respectively (p = .023, p = .016, p = .018). Moreover, changes in circulating levels of estradiol-17β in females after the trials do not depend on their reproductive status or on the outcome of the contest. We suggest that female aggression is associated with initial levels of estradiol-17β, and that the challenge hypothesis, originally defined for androgens, could also be extended to estrogens.

Territory defense as a condition-dependent component of male reproductive success in Drosophila serrata.

Sexual selection arises from both intrasexual competition and mate choice. With respect to the evolution of male traits, there is a vast literature documenting the existence of female choice and male-male competition, and both have been shown to co-occur in many species. Despite numerous studies of these two components of male reproductive success in isolation, few have investigated whether and how they interact to determine total sexual selection. To address this, we investigate male territoriality in Drosophila serrata, a species in which female preference for male sexual pheromones (cuticular hydrocarbons or CHCs) have been extensively studied. We demonstrate that territoriality occurs, that it involves direct male-male aggressive interactions, and that it contributes to variation in male mating success. Results from a phenotypic manipulation also indicate that territorial success is condition-dependent, although a genetic manipulation of condition, involving three generations of full-sib inbreeding, failed to find a significant effect. Finally, selection assays also suggest that territorial success depends on male body size but not on CHCs, whereas the opposite is true for mating success.

High-Pitched Notes during Vocal Contests Signal Genetic Diversity in Ocellated Antbirds

Animals use honest signals to assess the quality of competitors during aggressive interactions. Current theory predicts that honest signals should be costly to produce and thus reveal some aspects of the phenotypic or genetic quality of the sender. In songbirds, research indicates that biomechanical constraints make the production of some acoustic features costly. Furthermore, recent studies have found that vocal features are related to genetic diversity. We linked these two lines of research by evaluating if constrained acoustic features reveal male genetic diversity during aggressive interactions in ocellated antbirds (Phaenostictus mcleannani). We recorded the aggressive vocalizations of radiotagged males at La Selva Biological Station in Costa Rica, and found significant variation in the highest frequency produced among individuals. Moreover, we detected a negative relationship between the frequency of the highest pitched note and vocalization duration, suggesting that high pitched notes might constrain the duration of vocalizations through biomechanical and/or energetic limitations. When we experimentally exposed wild radiotagged males to simulated acoustic challenges, the birds increased the pitch of their vocalization. We also found that individuals with higher genetic diversity (as measured by zygosity across 9 microsatellite loci) produced notes of higher pitch during aggressive interactions. Overall, our results suggest that the ability to produce high pitched notes is an honest indicator of male genetic diversity in male-male aggressive interactions.

Mating dominance amongst male Himalayan tahr: Blonds do better

In ungulates, rank order is determined by differences in weight, body size, weapon size and age. In the Caprini tribe (Bovidae: Caprinae), adult male Himalayan tahr are unique to show different coat colours, but no sexual dimorphism in weapons. A highly significant correlation between hair colour and rank order was found during the rut: males with a lighter coloured ruff dominated over darker ruffed ones, in both aggressive interactions and access to oestrus females. We studied colour-based dominance in relation to weight, age and testosterone levels, which establish the social rank in most ungulates. No differences in weight and testosterone concentrations were found between adult male colour classes, but males with paler ruffs were significantly younger than darker adult males. The distribution of physical traumas from fights confirmed that younger, lighter-coloured males had a higher rank than older, darker males, a pattern which is unusual amongst ungulates. Coat colour seems to work as a signal of rank in male-male aggressive interactions and it changes according to age, whereas the relevant physiological determinants deserve further research. Intrasexual male competition has not changed weapon size or shape in the Himalayan tahr, but ruff colours are apparently used to signal rank and dominance. Colour patterns of adult males may then be homologous to ritualised weapons, apparently being a unique feature of male tahr amongst mammals.

Do male barn swallows ( Hirundo rustica ) experience a trade-off between the expression of multiple sexual signals?

Some sexual selection models envisage exaggerated male secondary sexual characters to be costly and therefore reliable indicators of the quality of potential mates to choosy females. If male secondary sexual characters have a natural selection cost, they may be linked to each other by reciprocally constraining relationships that would prevent individual males from increasing their level of multiple signaling. Barn swallow (Hirundo rustica) males have at least two costly signals relevant to socio-sexual interactions: tail length and song. Under the hypothesis that a trade-off exists between male signals, we manipulated the maintenance cost of tail ornaments to test whether this reduced the quantity and quality of song, a condition-dependent, phenotypically plastic signal. Contrary to our expectation, tail elongation had no effect on singing activity and song complexity. However, tail-elongated males produced songs with longer terminal parts ('rattles'). Long rattles are associated with highly competitive social contexts and high circulating levels of testosterone, suggesting that tail-elongated males were more frequently involved in either male-male aggressive or inter-sexual interactions. Therefore, this study shows that males are not displaying multiple signals at the maximum possible level, implying that this system is open to unreliable communication. However, long-term trade-offs between signal expression and viability may prevent males from displaying both signals at higher rates.

COURTSHIP BY SUBORDINATE MALE SIAMESE FIGHTING FISH, BETTA SPLENDENS: THEIR RESPONSE TO EAVESDROPPING AND NAÏVE FEMALES

[In a social environment, a communication signal may provide information to individuals other than those interacting with the signaler. Eavesdropping is gathering information without being directly involved in the communication interaction. Female Siamese fighting fish, Betta splendens , choose the winner of male-male aggressive interactions based upon information she extracts from eavesdropping. Naive females, those that have not witnessed the interaction, show no consistent preference for either male. This suggests that losers would be more successful in courting a naive female. We conducted two sets of trials: one set tested the losers' courting preference of eavesdropping females or naive females whereas the other tested the winners' courting preference. We found that losers displayed gill cover erection, a courting behaviour, significantly more towards the naive female than towards the eavesdropping female whereas the winner showed no preference. These results suggest that male B. splendens can moderate their response to an audience in ways more complex than previously appreciated. Our data support the suggestion that communication can serve as a network that reaches beyond the immediate signaler and receiver. Understanding the complexity of communication networks will enable us to broaden our ideas about the mechanisms of sexual selection., In a social environment, a communication signal may provide information to individuals other than those interacting with the signaler. Eavesdropping is gathering information without being directly involved in the communication interaction. Female Siamese fighting fish, Betta splendens , choose the winner of male-male aggressive interactions based upon information she extracts from eavesdropping. Naive females, those that have not witnessed the interaction, show no consistent preference for either male. This suggests that losers would be more successful in courting a naive female. We conducted two sets of trials: one set tested the losers' courting preference of eavesdropping females or naive females whereas the other tested the winners' courting preference. We found that losers displayed gill cover erection, a courting behaviour, significantly more towards the naive female than towards the eavesdropping female whereas the winner showed no preference. These results suggest that male B. splendens can moderate their response to an audience in ways more complex than previously appreciated. Our data support the suggestion that communication can serve as a network that reaches beyond the immediate signaler and receiver. Understanding the complexity of communication networks will enable us to broaden our ideas about the mechanisms of sexual selection.]

Male dominant/subordinate relationships, cuticular profiles and sex pheromone in Nauphoeta cinerea (Dictyoptera, Blaberidae)

In the cockroach Nauphoeta cinerea, male-male aggressive interactions result in dominant-subordinate relationships. Once dominance relationships are established, a male can recognize the status of another individual, likely through chemical cues. The aim of this study was to determine the effect of these male-male interactions on cuticular chemical profiles and on the relative composition of the male sex pheromone. The results of chemical analyses of males reared in pairs for 30 days clearly showed significant differences in both cuticular profiles and sex pheromone of dominant and subordinate individuals. The possible role of these compounds as recognition cues was discussed.

Does Brood Size Manipulation Affect Later Competitive Behaviour of Offspring?

AbstractData from several field experiments support the existence of a trade-off between number and quality of offspring. However, long term effects of brood size on fitness related traits of offspring have been a relatively neglected area of research. In a laboratory experiment the effect of manipulated brood size on subsequent competitive ability of adult offspring was investigated. Zebra finches, Taeniopygia guttata, were reared in small or large broods and young were exchanged in such a way that natural siblings from different rearing conditions could be compared. Competitive behaviour was assessed in two different contexts: competition for food (both sexes tested) and competition for mates (only males tested). There was no significant difference between males from small and large broods in number of succesfull attacks (after which the other male moved away) during male-male aggressive interactions provoked by the presentation of a female in an adjacent cage. Nor did brood size affect latency to eat, time spent eating or success at displacing the other bird from the feeder during food competition tests. The results thus suggest consistently that later competitive ability of offspring is not affected by brood size in this species.

Female Aquatic Warblers (Acrocephalus Paludicola) Are Attracted By Playback of Longer and More Complicated Songs

Abstract Male aquatic warblers are relatively unusual in producing three different song structures, A, B and C. The shorter A-B songs have been shown to function in male-male aggressive interactions, and it was speculated that the longer and more complex C songs might function in female attraction. The present playback experiments were carried out on hormone-implanted females in a large, experimental aviary. When playback was of a male singing C songs, females were attracted faster and for longer periods than when the same male produced A-B songs. Females gave relatively few sexual displays, but gave more in response to playback of C songs than to A-B songs. Aquatic warblers have an unusually promiscuous mating system with high rates of extra-pair fertilisation and multiple paternity within broods. Sexual selection through intense sperm competition may have accentuated the evolution of structurally distinct songs for female attraction and aggressive interactions between rival males.

Behavioural influences on male mating success in the Oriental fruit fly, Dacus dorsalis Hendel

Variation in male mating success in a laboratory population of Dacus dorsalis was studied by dividing mating success into the components of mate attraction and subsequent copulation. Female responses to male signals at both the attraction and pre-copulatory phases were measured in a set of reciprocal experiments: males were scored for attractiveness followed by copulatory success, or in the reverse order. In the first tests, only 38% of the males attracted females, and of these, 74% were successful in mating. When attraction was measured after the copulation tests, 94% of successfully mated males elicited female approaches. Thus, females consistently preferred the same males, whether detecting them via long-distance signals or interacting at close range. Male-male aggressive interactions were studied in a separate experiment; males with high rates of copulatory success were also successful in inter-male competition. Dominant males were the most active at producing long-range attraction signals. Thus, female mating preferences and inter-male competition appear to have a similar influence on mating success of D. dorsalis males.

The influence of body size and prior residency on the outcome of male-male interactions ofMarpissa marina, a New Zealand jumping spider (Araneae Salticidae)

In experiments, body size and prior residency at nests are shown to be factors that influence the outcome of male-male aggressive interactions of Marpissa marina, a New Zealand jumping spider. Away from nests, larger males tend to win, but at nests the occupant tends to win. Possible reasons for M. marina male-male conflict being settled by these rules are discussed. The larger question of why salticid males are aggressive is also discussed.

Reproductive Behavior and Sexual Dimorphism of a Caprellid Amphipod

The reproductive sequence of Caprella laeviuscula Mayer consisted of pair formation, female molting, copulation, pair disengagement, and egg laying. The male held the female with the fifth pereiopods during precopula and removed the exoskeleton of the female prior to copulation. The number of eggs carried by the female was a function of female size, and the number of juveniles carried was significantly lower than the number of eggs carried by similarly sized females. Some of the eggs may have functioned as nurse eggs. Cephalon length was determined to be the best character for analysis of sexual dimorphism in this species. Among sexually mature specimens, males had more rapid differential growth of pereionites 1 and 2, while female pereionites 3-7 grew more rapidly. In addition to exhibited growth rates, sexual dimorphism was evident in the brood pouch of females, and in the point of insertion of gnathopod 2. The differences could not be related to male-female reproduction, and sexual dimorphism of males probably is a response to the male-male aggressive interactions during precopulation.

Kinship, familiarity, aggression, and dominance in deer mice (Peromyscus maniculatus) in seminatural enclosures.

This study was designed to test the effects of kinship and postweaning familiarity on male-male aggressive interactions in deer mice (Peromyscus maniculatus) in a more naturalistic situation than that of most tests of kin discrimination. Familiar males (i.e., those housed together from weaning) displayed significantly less aggression than unfamiliar males; kinship per se did not appear to affect levels of aggression. In addition, dominant males copulated more than subordinates and under some conditions sired more offspring. The postest copulatory patterns showed that the subordinate males ejaculated after fewer intromissions than did dominant males.

The role of male vs male interactions in maintaining population dialect structure

Nonmigratory populations of Whitecrowned Sparrows in coastal California exhibit dialects in territorial male songs that are stable in space and time. By field playback experiments, we tested a prediction from the hypothesis that male aggressive interactions prohibit mixing of song dialects. Playback of the home dialect ‘Clear’ song to territorial males singing the ‘Clear’ dialect resulted in less response than that given to playback of the neighboring ‘Buzzy’ dialect. Response to both ‘Buzzy’ and ‘Clear’ dialect songs by target ‘Clear’ males, however, was greater than that given to the ‘Bodega’ dialect recorded 55 km away (Figs. 2 and 3). We conclude that these results are consistent with the hypothesis that male-male aggressive interactions play an important role in reducing dialect mixing.

Lek Social Organization and Reproductive Success in the Greater Prairie Chicken

Between 1964 and 1969, studies were made of Prairie Chicken reproductive behavior on a lek with a stable social organization. The social organization of this lek was altered by the removal of dominant males; three in 1970 and two in 1971. Social organization and reproductive behavior were observed on this lek prior to and following removal of the dominant males. Removal of dominant males disrupted the stable social organization on the lek. Total number of aggressive interactions between males increased following removal of dominant males. No change was noted in the total number of females visiting the lek in 1970 compared with the previous 6-year period. Likewise, no change was noted in the number of attempted copulations observed in 1970 compared with previous years. However, the number of successful copulations was drastically reduced (90% fewer) during 1970 because of increased male-male aggressive interactions on the lek. During 1971, fewer territorial males were on the lek compared to previous years, and fewer females visited the lek and fewer successful copulations were recorded than in previous years. Late nests of Prairie Chickens are less successful and contain fewer eggs compared with nests begun earlier. In some instances, the female social hierarchy may serve to delay onset of nesting, therefore reducing total reproduction for the year.