Male Mating Tactics Research Articles

Oxytocin receptor density is associated with male mating tactics and social monogamy

Despite its well-described role in female affiliation, the influence of oxytocin on male pairbonding is largely unknown. However, recent human studies indicate that this nonapeptide has a potent influence on male behaviors commonly associated with monogamy. Here we investigated the distribution of oxytocin receptors (OTR) throughout the forebrain of the socially monogamous male prairie vole (Microtus ochrogaster). Because males vary in both sexual and spatial fidelity, we explored the extent to which OTR predicted monogamous or non-monogamous patterns of space use, mating success and sexual fidelity in free-living males. We found that monogamous males expressed higher OTR density in the nucleus accumbens than non-monogamous males, a result that mirrors species differences in voles with different mating systems. OTR density in the posterior portion of the insula predicted mating success. Finally, OTR in the hippocampus and septohippocampal nucleus, which are nuclei associated with spatial memory, predicted patterns of space use and reproductive success within mating tactics. Our data highlight the importance of oxytocin receptor in neural structures associated with pairbonding and socio-spatial memory in male mating tactics. The role of memory in mating systems is often neglected, despite the fact that mating tactics impose an inherently spatial challenge for animals. Identifying mechanisms responsible for relating information about the social world with mechanisms mediating pairbonding and mating tactics is crucial to fully appreciate the suite of factors driving mating systems.This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Personality traits, reproductive behaviour and alternative mating tactics in male European bitterling, Rhodeus amarus

Individual differences in behavioural traits may play a role in reproductive behaviour and it is likely that different personality types have different reproductive success across specific social environments. This suggests a role for sexual selection for personality types, including a link between behavioural traits and alternative reproductive tactics. While research on morphological differences between guarders (bourgeois males defending resources) and sneakers (males parasitizing the territories of bourgeois males) is well characterized, the role of personality in the adoption of alternative mating tactics has hitherto been largely ignored. We investigated individual behavioural differences in a sneaker‐guarder mating system using size/age-matched males of a small freshwater fish, the European bitterling (Rhodeus amarus). We predicted distinct behavioural responses by guarder and sneaker males that were consistent in different contexts, indicating the existence of behavioural syndromes associated with male mating tactic. No behavioural syndromes were detected in male R. amarus, despite ability of individual male bitterling to establish dominance, boldness and investment in sperm competition being relatively repeatable across three consecutive trials. Male aggression, though not repeatable, was negatively correlated with the number of ejaculations, indicating a trade-off between aggression and sperm loading. No association between the tendency of males to guard a territory and behavioural traits was found, despite a significant association between the tendency to guard and morphological and physiological traits, with higher relative testis size and more breeding tubercles in guarder males. Our data suggest male bitterling mating tactics are largely unconstrained by innate factors and likely to be the product of prevailing environmental and social conditions.

Male Mating Tactics in Captive Rhesus Macaques (Macaca mulatta): The Influence of Dominance, Markets, and Relationship Quality

Male mating success in a multimale–multifemale group can depend on several variables: body condition, dominance, coalitions, “friendship,” or an exchange of services for mating access. Exchange patterns may also be determined by market effects or social relationships. We studied the mating tactics of males in a captive, multimale–multifemale group of rhesus macaques and the resulting patterns of mating and paternity to determine the influence of dominance rank, mating markets, and relationship quality on their mating tactics. Male rank was positively related to the total number of copulations and the number of mating partners, but did not explain male mating distribution completely. Moreover, male fertilization success was not related to male rank. Males did not exchange grooming for mating access on the same day and neither the supply nor the rank (as a proxy for quality) of receptive females affected the amount of male grooming, suggesting that market effects did not explain male mating access. However, there was a positive correlation between long-term grooming patterns of both males and females and mating access, indicating that social relationships were important for male mating access. Paternity data revealed that these social relationships were also important for male reproductive success. We conclude that both male rank and male–female “friendship” determined male mating access in these rhesus macaques, but that “friendship” was more important in determining paternity, emphasizing the importance of intersex social bonds in male mating success in multimale primate societies.Electronic supplementary materialThe online version of this article (doi:10.1007/s10764-011-9552-5) contains supplementary material, which is available to authorized users.

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

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

Competition and Opportunity Shape the Reproductive Tactics of Males in the Ant Cardiocondyla obscurior

Context-dependent adjustment of mating tactics can drastically increase the mating success of behaviourally flexible animals. We used the ant Cardiocondyla obscurior as a model system to study adaptive adjustment of male mating tactics. This species shows a male diphenism of wingless fighter males and peaceful winged males. Whereas the wingless males stay and exclusively mate in the maternal colony, the mating behaviour of winged males is plastic. They copulate with female sexuals in their natal nests early in life but later disperse in search for sexuals outside. In this study, we observed the nest-leaving behaviour of winged males under different conditions and found that they adaptively adjust the timing of their dispersal to the availability of mating partners, as well as the presence, and even the type of competitors in their natal nests. In colonies with virgin female queens winged males stayed longest when they were the only male in the nest. They left earlier when mating partners were not available or when other males were present. In the presence of wingless, locally mating fighter males, winged males dispersed earlier than in the presence of docile, winged competitors. This suggests that C. obscurior males are capable of estimating their local breeding chances and adaptively adjust their dispersal behaviour in both an opportunistic and a risk-sensitive way, thus showing hitherto unknown behavioural plasticity in social insect males.

Variation in number of copulations in Theclini butterfly females (Lycaenidae: Lepidoptera)

AbstractThe number of spermatophores inseminated in the bursa copulatrix of females of 21 species of Theclini butterflies varied from 0 to 38, a maximum much larger than reported so far. The variation of spermatophore number observed was analyzed on a phylogenetic tree recently determined, together with variation of wing colors and male mating tactics. Monandrous species tended to be sexually dimorphic in wing color and associated with male territoriality.

Male Responses to Conspecific Advertisement Signals in the Field Cricket Gryllus rubens (Orthoptera: Gryllidae)

In many species males aggregate and produce long-range advertisement signals to attract conspecific females. The majority of the receivers of these signals are probably other males most of the time, and male responses to competitors' signals can structure the spatial and temporal organization of the breeding aggregation and affect male mating tactics. I quantified male responses to a conspecific advertisement stimulus repeatedly over three age classes in Gryllus rubens (Orthoptera: Gryllidae) in order to estimate the type and frequency of male responses to the broadcast stimulus and to determine the factors affecting them. Factors tested included body size, wing dimorphism, age, and intensity of the broadcast stimulus. Overall, males employed acoustic response more often than positive phonotactic response. As males aged, the frequency of positive phonotactic response decreased but that of the acoustic response increased. That is, males may use positive phonotaxis in the early stages of their adult lives, possibly to find suitable calling sites or parasitize calling males, and then later in life switch to acoustic responses in response to conspecific advertisement signals. Males with smaller body size more frequently exhibited acoustic responses. This study suggests that individual variation, more than any factors measured, is critical for age-dependent male responses to conspecific advertisement signals.

An experimental test for alternative reproductive strategies underlying a female‐limited polymorphism

Polymorphism often corresponds to alternative mating tactics in males, but much less is known about this relationship in females. However, recent work suggests that selection for alternative reproductive strategies in females can maintain genetic variation in important life-history traits. Brown anole lizards (Anolis sagrei) exhibit a genetically based polymorphism in dorsal pattern that is expressed only by females, which occur in bar (B), diamond (D) and intermediate diamond-bar (DB) morphs. Here, we use a combination of natural history data, captive breeding studies and phenotypic manipulations of reproductive investment to test the hypothesis that this polymorphism corresponds to morph-specific patterns of reproductive investment. Three years of data from wild females and two generations of captive breeding revealed no differences among morphs in the frequency of egg production or in the number, frequency, size or sex ratio of offspring. Manipulations of reproductive investment via surgical ovariectomy revealed significant costs of reproduction with respect to survival, growth, immune function and haematocrit, but the magnitudes of these costs did not differ among morphs. Collectively, our results refute the hypothesis that this sex-limited polymorphism is maintained by selection for alternative reproductive strategies. We compare this finding to other systems in which polymorphic females exhibit alternative reproductive tactics and discuss other selective factors that could maintain polymorphism in anoles.

Correlation between Male Social Status, Testosterone Levels, and Parasitism in a Dimorphic Polygynous Mammal

Life history trade-offs have often been assumed to be the consequence of restrictions in the availability of critical resources such as energy and nutrients, which necessitate the differential allocation of resources to costly traits. Here, we examined endocrine (testosterone) and health (parasite burdens) parameters in territorial and non-territorial New Zealand fur seal males. We documented intra-sexual differences in sexual behaviours, testosterone levels, and parasitism that suggest a trade-off exists between reproductive success and physical health, particularly susceptibility to helminths and acanthocephalans, in males displaying different mating tactics (i.e., territorial and non-territorial tactics). Levels of testosterone were higher in territorial males and correlated positively with reproductive effort (i.e., intra- and inter-sexual interactions). However, these territorial males also exhibited high levels of parasitic infection, which may impair survival in the long-term. Our study, while limited in sample size, provides preliminary evidence for a link between male mating tactics, testosterone levels and parasite loads, and potential effects on reproductive success and life history that should be explored further.

Male mating tactics in spider monkeys: sneaking to compete

I investigated the mating system and male mating tactics for a population of wild spider monkeys (Ateles belzebuth chamek), to identify the behaviors males used to achieve and maintain access to sexually receptive females, and to examine if some males used more tactics than other males and/or had differential access to females. Results show that the mating system mostly involved scramble competition polygyny and that males used a range of mating tactics and behaviors, previously unreported for spider monkeys. The most unusual feature of spider monkey mating behavior was the secretive nature of copulations-nearly all copulations were clandestine, but a few were in the presence of other group members. Fifteen sexually mature males were observed to copulate 43 times. These data provide the first opportunity to evaluate how female availability influences male-male competition. First, the operational sex ratio was highly skewed toward males because usually only one female was receptive in each community per month. Second, females only mated with a few males in their community in any one mating period, but some females mated over the course of multiple consecutive mating periods, eventually mating with most or all of the males in their community. Across all communities, 9 (21%) of the 43 copulations involved a single male-female partner, 20 (47%) involved four males mating with the same female, and males mated with from one to four different females. Fourteen of the 16 total adult males and 1 subadult male (10 total) copulated. One or two males in each community were successful in monopolizing access to receptive females, and these males did not usually have the highest rates of copulation. In this system, clandestine copulations are one behavioral solution to the complex problem of gaining mating exclusivity and, probably, exercising mate choice.

Alternative male mating tactics in Hypoptychus dybowskii (Gasterosteiformes): Territoriality, body size and nuptial colouration

Alternative male mating tactics in Hypoptychus dybowskii (Gasterosteiformes): Territoriality, body size and nuptial colouration

Experimental demonstration of alternative mating tactics of male Ptilothrix fructifera (Hymenoptera, Apidae)

Ptilothrix fructifera is a solitary, oligolectic bee dependent on the flowers of Opuntia (Cactaceae). We conducted field studies to identify the mating tactics used by P. fructifera males and to determine whether factors such as male body size and available resource flowers contribute to variation in male mating tactic. Males in a population in southern Brazil showed pronounced variation in body size, but no distinct size classes. Larger males aggressively defended territories of flowering Opuntia plants, the sole pollen source for the females. Smaller males nonaggressively patrolled nonflowering shrubs growing between the nest aggregation and patches of Opuntia . Only unmated females were attractive to males. When offered to males in patrolled shrubs, up to eight males attempted to mate with the same female, but in territories only the territory owner mated with the introduced female. About 10 min after mating, females were unattractive to males. These results identify the species as monogamous and indicate that territoriality is an adaptive mating tactic. Experimental addition of Opuntia flowers to patrolled shrubs showed that nonterritorial males can switch to territorial behaviour. Thus, the number of available flowers together with the number of competitor males determines the ratio of territorial males to patrolling males at a given site. The experiment shows that male P. fructifera show a conditional reproductive strategy in which males adopt alternative tactics according to their size.

Geographic variation in sperm traits reflects predation risk and natural rates of multiple paternity in the guppy

Guppies (Poecilia reticulata) are models for understanding the interplay between natural and sexual selection. In particular, predation has been implicated as a major force affecting female sexual preferences, male mating tactics and the level of sperm competition. When predation is high, females typically reduce their preferences for showy males and engage more in antipredator behaviours, whereas males exploit these changes by switching from sexual displays to forced matings. These patterns are thought to account for the relatively high levels of multiple paternity in high-predation populations compared to low-predation populations. Here, we assess the possible evolutionary consequences of these patterns by asking whether variation in sperm traits reflect differences in predation intensity among four pairs of Trinidadian populations: four that experience relatively low levels of predation from a gape-limited predator and four that experience relatively high levels of predation from a variety of piscivores. We found that males in high-predation populations had faster swimming sperm with longer midpieces compared to males in low-predation populations. However, we found no differences among males in high- and low-predation populations with respect to sperm number, sperm head length, flagellum length and total sperm length.

Acoustic Experience Shapes Alternative Mating Tactics and Reproductive Investment in Male Field Crickets

Developmental plasticity allows juvenile animals to assess environmental cues and adaptively shape behavioral and morphological traits to maximize fitness in their adult environment. Sexual signals are particularly conspicuous cues, making them likely candidates for mediating such responses. Plasticity in male reproductive traits is a common phenomenon, but empirical evidence for signal-mediated plasticity in males is lacking. We tested whether experience of acoustic sexual signals during juvenile stages influences the development of three adult traits in the continuously breeding field cricket Teleogryllus oceanicus: male mating tactics, reproductive investment, and condition. All three traits were affected by juvenile acoustic experience. Males of this species produce a long-range calling song to attract receptive females, but they can also behave as satellites by parasitizing other males' calls. Males reared in an environment mimicking a population with many calling males were less likely to exhibit satellite behavior, invested more in reproductive tissues, and attained higher condition than males reared in a silent environment. These results contrast with other studies and demonstrate how the effects of juvenile social experience on adult male morphology, reproductive investment, and behavior may subsequently influence sexual selection and phenotypic evolution.

Effect of body size and sex ratio on male alternative mating tactics of the West Indian sweetpotato weevil, Euscepes postfasciatus

AbstractMale body size is considered to be one of the major determinants of mating success among many insect species. Because the effectiveness of the sterile insect technique (SIT) depends on the ability of released sterile males to mate with and inseminate wild females, it is indispensable to understand the effect of male body size on the mating behavior of both sexes for the progress of the SIT program. We investigated how male body size and the presence of other rival males affect the guarding and copulatory durations of the West Indian sweetpotato weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae). In this species, males guard females before and after copulation. By observing the mating behavior under two sex‐ratio conditions (male‐to‐female ratios of 1:1 and 2:1), we found that small males hastened to court females when rival males were present, but the females rejected these small males as mates. Therefore, we consider that female weevils adopt a counter‐adaptation for mate preference in response to this male mating strategy. Body size did not affect the durations of copulation and post‐copulatory guarding. Although we found a conditional mating strategy for body size in E. postfasciatus, it is unlikely to have a large influence on the weevil‐eradication program using SIT.

Male-male and male-female aggression may influence mating associations in wild octopuses (Abdopus aculeatus).

Abdopus aculeatus engages in frequent aggression and copulation, exhibits male mate-choice, and employs multiple mating tactics. Here we draw upon established hypotheses to compare male-male aggression (MMA) and male-female aggression (MFA), as they relate to their mating behavior in the wild. When contesting for females, males appear to balance mate preference (resource value) with perceived chances of winning contests (resource holding potential). Although males spent more time mating with and contesting for large "Adjacent Guarded" females (those occupying a den within arm's reach of a large "Adjacent Guarding" male), they exhibited higher rates of aggression over nonadjacent "Temporarily Guarded" females that may be more accessible. The major determinant of male-male aggressive success was size, and this factor may dictate the expression of conditional mating tactics in males. "Adjacent Guarding" males were the largest and most aggressively successful males, earning the most time copulating with females. They are considered to have the highest resource holding potential (RHP) in MMA. By contrast, in MFA, some larger individuals fled from smaller individuals, indicating that RHP appears to be a function of both size and sex in intersexual aggression. This result suggests variation in aggressiveness, or potential for severe injury-even sexual cannibalism during MFA. Male-female aggression may also be influenced by the sexual nonreceptivity of some individuals, or attempts by both sexes to increase foraging behavior by delaying mate-guarding activity.

Short term changes in sex ratio and density alter coercive male mating tactics

AbstractShort term fluctuations in operational sex ratio (OSR) and density can strongly influence male mating, often exacerbating conflict between males and females. Livebearing fishes of the genus Gambusia are ideal for investigating sexual conflict because males of all sizes mate coercively. In this study, we tested how short-term fluctuations in OSR and density influence coercive male mating behaviours. Specifically, we tested the prediction that as OSR becomes more female biased, males will mate with all available females. In contrast, as OSR becomes more male biased, male aggression will inhibit mating frequency. As predicted, males mated with more females as the number of available females increased. Moreover, males were less aggressive as the proportion of females increased and more aggressive as the number of males increased. This resulted in an inverse relationship between mating and aggression with OSR and density. Coercive males attempt to maximize their reproductive success by mating with all available females, which supports classic theory on the impact of OSR and density on reproductive activity.

Seasonal changes in reproductive and physical condition, sexual dimorphism, and male mating tactics in the jewelled blenny Salarias fasciatus

To investigate seasonal changes in reproductive and physical condition, sexual dimorphism, and mating tactics in the jewelled blenny Salarias fasciatus, monthly collections were conducted on the fringing reef in northern Okinawa, Japan. Monthly variation in the female gonadosomatic index suggested that the breeding season of this species is from April to June. The physical condition and hepatosomatic index of both sexes considerably deteriorated during the course of the breeding season. Such declines may be primarily due to egg production in females and brood care in males. Males’ elongated anal spines were longer than females’, but no other apparent sexual dimorphisms were detected, indicating that S. fasciatus exhibits a low degree of sexual dimorphism. Examinations of testes size and the testicular gland area during the estimated breeding season revealed that the gonadosomatic index values of smaller males did not differ from those of larger males. This result may differ from other blenny species that exhibit alternative male reproductive tactics. However, patterns of male testicular glands of S. fasciatus were similar to those of other blennies with alternative tactics, i.e., smaller males had poorly developed testicular glands compared with larger males.

Terry Burke - recipient of the 2009Molecular EcologyPrize

Terry Burke - recipient of the 2009<i>Molecular Ecology</i>Prize

Love bites: male fang use during coercive mating in wolf spiders

Evolutionary conflicts of interest between the sexes are common, as mating tactics and strategies that increase fitness benefits for one sex may incur costs for the other. As a consequence, antagonistic coevolution between the sexes often results in a complex arms race between male persistence and female resistance. Coercive mating (e.g., forced copulation) likely benefits males by increasing the probability of mating; however, costs to females may be high, including injury or even death. Here, we report on a study of the use of fangs by males of the wolf spider Schizocosa ocreata (Hentz) during forcible mating with resistant females, which results in hemolymph loss and scar tissue formation in females. Microscopic inspection revealed that fang wounds (evidenced by scar tissue) were absent on unmated (virgin) females but were found on mated females and were significantly more frequent in coercively mated females. Experimental fang immobilization studies found no difference in copulation success between experimental (fangs immobilized) and control (sham manipulation) males. However, males that had use of their fangs had significantly longer copulation duration. These findings represent a previously unknown male mating tactic in spiders and an unrecognized potential cost of mating for female spiders.