Male reproductive success in harem troops of hanuman langurs (Presbytis entellus)

Based on cross-sectional and longitudinal data collected in 1967–1988 by various observers, male reproductive success was studied in the Hanuman langurs of Jodhpur, India. The harem-structured social organization ensures a high degree of paternity certainty. Births occur throughout the year, with significant peaks and minima in March and November, respectively (n =398).The interbirth interval averages 16.7 months (n = 114).The duration of harem residencies varies between 3 days and ≥ 74.0 months, with a mean of 26.5 (n = 64). Harem holder replacements occur during all months of the year. No male achieves residency in more than one troop, suggesting that residency is associated with a distinct peak in the resource holding potential of a given male. Reproductive success among males varies considerably. Male mortality is high due to migration and intrasexual competition, leading to an adult sex ratio of 1:4.9. It is estimated that one-quarter of all adult males will never gain harem residency. Conceptions achieved outside harem residencies are so rare (4.7%) that a viable low-risk strategy, opting for longevity instead of harem residency, is unlikely. Tenure length has a stronger influence on male reproductive success than harem size because interbirth intervals are significantly shorter in small harems than in larger ones. It is assumed that females in one-male breeding structures compete for sperm and that such competition is more intense in larger harems.     

Variance in the reproductive success of dominant male mountain gorillas

Using 30 years of demographic data from 15 groups, this study estimates how harem size, female fertility, and offspring survival may contribute to variance in the siring rates of dominant male mountain gorillas throughout the Virunga Volcano Region. As predicted for polygynous species, differences in harem size were the greatest source of variance in the siring rate, whereas differences in female fertility and offspring survival were relatively minor. Harem size was positively correlated with offspring survival, even after removing all known and suspected cases of infanticide, so the correlation does not seem to reflect differences in the ability of males to protect their offspring. Harem size was not significantly correlated with female fertility, which is consistent with the hypothesis that mountain gorillas have minimal feeding competition. Harem size, offspring survival, and siring rates were not significantly correlated with the proportion of dominant tenures that occurred in multimale groups versus one-male groups; even though infanticide is less likely when those tenures end in multimale groups than one-male groups. In contrast with the relatively small contribution of offspring survival to variance in the siring rates of this study, offspring survival is a major source of variance in the male reproductive success of western gorillas, which have greater predation risks and significantly higher rates of infanticide. If differences in offspring protection are less important among male mountain gorillas than western gorillas, then the relative importance of other factors may be greater for mountain gorillas. Thus, our study illustrates how variance in male reproductive success and its components can differ between closely related species.     

Male reproductive success and its behavioural correlates in a polygynous mammal,the Galápagos sea lion (Zalophus wollebaeki)

Sexual selection theory predicts competitive males and choosy females. Nevertheless, since molecular marker‐based studies, paternity outside the expected mating patterns has increasingly been described. Even in highly polygynous systems, where paternity is expected to be strongly skewed towards large, dominant males, alternative mating tactics have been suggested. We examined reproductive success in the polygynous Galápagos sea lion (Zalophus wollebaeki). Semiaquatic territoriality allows females to move freely and may lower the degree of polygyny otherwise suggested by both territorial behaviour and strong sexual dimorphism. We assigned paternities with 22 microsatellites and analysed how male reproductive success was related to size, dominance status, intra‐sexual agonistic behaviour, proximity to females, and attendance in the colony. Male behaviour was consistent across two seasons for all parameters under consideration. Attendance was by far the most important determinant of paternal success. Skew in reproductive success towards large, dominant males was weak and dominance status played no role. This appears to be caused by an extremely long reproductive season lasting five or more months, making it difficult for any male to monopolize receptive females. Females seem to choose displaying males that were present in the colony for a long time rather than dominance per se. Sexual dimorphism in Galápagos sea lions may thus be more influenced by selection for fasting than fighting ability. Our data provide further evidence for alternative mating tactics, as several males gained relatively high reproductive success despite short attendance and hardly any involvement in agonistic interactions.     

Extreme polygyny among southern elephant seals on Sea Lion Island, Falkland Islands

Elephant seals are known from long-term behavioral studies tobe highly polygynous and to show high variance in reproductivesuccess among males. However, genetic studies have determinedthat the level of polygyny varies between the closely relatednorthern and southern elephant seals. In the present study,we investigate paternal success at the Sea Lion Island southernelephant seal colony in the Falkland Islands by using both behavioralmeasures and genetic markers. We find that the average successof harem holding males at Sea Lion Island is significantly higherthan both the northern species and the nearby southern elephantseal population at Punta Delgada. We compare genetic paternitywith various behavioral indices of male mating success, andwe find that the behavioral measures provide a good estimateof the variance in male reproductive success. Only 28.2% ofmales achieved paternities, and among these, harem holders accountedfor 89.6%. We discuss the implications of our results in thecontext of the demographic and physical environment. Specifically,a comparatively high variance in resource holding potentialamong males, differences in male social behavior, and a smalltidal cycle limiting peripheral male access during female departurefrom the harem at this colony may be important factors leadingto the comparatively high variance in male reproductive successat Sea Lion Island.     

Genetic mating system and the significance of harem associations in the bat Saccopteryx bilineata

We analysed the polygynous mating system of the bat Saccopteryx bilineata using behaviour observations and genetic data on 11 microsatellite DNA loci. Basic social units in S. bilineata are harem groups that consist of single males and up to eight females. Colonies comprise several harem groups, and the composition of colonies and harems is often stable over several reproductive seasons. The combination of parentage exclusion and likelihood-based parentage assignment in this study produced detailed parentage information for a large colony of S. bilineata. Reproduction occurred mostly within the colony (17% extra-colony paternity), but social associations in harems within the colony did not represent reproductive units (70% extra-harem paternity). The latter finding was consistent over three reproductive seasons. Spatial association of the roosting sites of males and females could not explain parentage patterns in the colony. Even though intra-harem paternity was less frequent than expected, it contributed significantly to reproduction of harem males. On average, the number of offspring sired by a male with females in his harem territory increased significantly with harem size, which corresponds to the higher energetic investment that is related to the maintenance of large harems. However, extra-harem paternity was not correlated with a male's harem size or intra-harem reproductive success. This suggests that individual preferences of females rather than male traits associated with the ability to defend large harems are most likely to cause the detected differences between social association and genetic mating system.     

Social mating system and reproductive success in house wrens

Current models explaining the establishment and maintenanceof social monogamy and polygyny within avian populations typicallyassume that the reproductive success of polygynous males exceedsthat of monogamous males. This assumption is almost always supportedwhen the number of fledglings or recruits to future breedingpopulations is used to measure adult reproductive success. However,recent studies using DNA markers indicate that simple countsof fledglings or recruits may be a poor estimator of the numberof nestlings sired by the social father. In this paper, we comparethe number of genetic offspring produced by socially monogamousand polygynous house wren (TrogiodyUs atdon) males in nestsat which they were the social father. Polygynous males did,in fact, sire more nestlings in their own nests than did monogamousmales. Moreover, although we have not identified the sires ofextrapair nestlings, we document that even when all extrapairnestlings in this population are hypotheticaOy assigned to monogamousmales, die total reproductive success of polygynous males exceedsthat of monogamous males. These results and those of severalother recent studies are consistent with the assumption thatpolygynous males produce more offspring than monogamous males.     

Male tactics and reproductive success in the harem polygynous bat Saccopteryx bilineata

Alternative tactics in reproductive behavior enable individualsto maximize their fitness in relation to competitors in thesame population. In many taxa, territoriality is a common tacticof males to increase their reproductive success. In the batSaccopteryx bilineata, territorial males defend roosting areasfor females against other males and court females throughout the year. Peripheral males in the same colonies do not defendterritories but compete with territorial males for reproductionwith females. In this study, we monitored the behavior of themales in a natural colony over three reproductive seasons.We compared morphological and age data and measured the reproductiveoutput of males adopting the territorial or peripheral tactic.No differences in body size or weight were detected betweenmale types, but the probability of adopting a tactic seemedto be age dependent. Peripherals were often young males andreplaced territorials in several cases, whereas the oppositecase was not observed. Peripherals were not excluded from reproduction,but territorials were more likely to reproduce. Variation in reproductive success was high within both male tactics, andthe reproductive success of some peripherals was comparableto territorials, but, on average, the reproductive successof territorials was more than twice as high. Therefore, behavioraltactics do not seem to be equally profitable in general butmay represent different phases in the reproductive life of manyS. bilineata males.     

Age-specific survival of territorial and non-territorial male chamois

How alternative reproductive tactics (ARTs) are maintained in wildlife populations is one of the major questions in evolutionary biology. As a dominant status, territoriality is typically linked to increased mating opportunities, and one explanation why this behaviour coexists with other tactics is that dominance implies survival costs. Such a trade-off may occur in the Northern chamois Rupicapra rupicapra, as reproductive advantages of territorial males over non-territorial males could be counterbalanced by a reduction in survival mediated through energy expenditure, stress and parasitic infections, ultimately favouring ART coexistence. Here, we analysed age-dependent survival probabilities of territorial (n = 15) and non-territorial (n = 16) adult chamois using information collected over 12 years between 2010 and 2021 in the Gran Paradiso National Park (Western Italian Alps). Survival rates were estimated with a CMR approach using Burnham's joint modelling of live encounter and dead recovery data. The model selection procedure, based on AICc value minimisation, supported a linear decrease of survival with age but the results did not match our predictions, as territorial chamois did not have lower survival rates than non-territorial chamois. In contrast, territorial males appeared to enjoy reproductive success at lower survival costs. This, in turn, supports the role of other factors, such as snow-dependent environmental stochasticity, in the maintenance of ARTs in chamois populations. The limited sample size, however, calls for caution in interpretation, and long-term studies of lifetime reproductive success and survival are necessary to clarify the mechanisms underlying the expression and coexistence of different reproductive behaviours in this species.     

Reproductive investment patterns,sperm characteristics,and seminal plasma physiology in alternative reproductive tactics of Chinook salmon (Oncorhynchus tshawytscha)

Although alternative reproductive tactics (ARTs) are common across a range of taxa, little is known about whether the different tactics have adapted to sperm competition risk. Chinook salmon, Oncorhynchus tshawytscha, have two ARTs: large males that participate in dominance‐based hierarchies for access to spawning females, known as hooknoses, and small males that attempt to sneak fertilizations during spawning events from peripheral positions, known as jacks. Jacks continually face sperm competition risk because they always spawn in the presence of another male, whereas hooknoses face relatively low sperm competition risk because other males are not always present during spawning events. Based on the sneak‐guard model of sperm competition this asymmetry in sperm competition risk predicts that jacks ought to invest significantly more into sperm‐related traits important for sperm competition success relative to hooknoses. In the present study we report on reproductive investment patterns, sperm characteristics, and seminal plasma physiology of males that exhibit ARTs in Chinook salmon. We found that jacks invest significantly more of their somatic tissue into gonads compared with hooknoses. Sperm velocity also varied significantly between the ARTs, with jacks having significantly faster sperm than hooknoses. No significant differences in seminal plasma physiology metrics related to sperm quality were detected between the ARTs. We interpret these sperm investment patterns in light of the sneak‐guard model of sperm competition that is based on differences in sperm competition risk and alternative investment possibilities among ARTs. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Alternative reproductive tactics in snail shell‐brooding cichlids diverge in energy reserve allocation

Life history theory predicts that the amount of resources allocated to reproduction should maximize an individual's lifetime reproductive success. So far, resource allocation in reproduction has been studied mainly in females. Intraspecific variation of endogenous energy storage and utilization patterns of males has received little attention, although these patterns may vary greatly between individuals pursuing alternative reproductive tactics (ARTs). ARTs are characterized by systematic variation of behavioral, physiological, and often morphological traits among same‐sex conspecifics. Some individuals may rely on previously accumulated reserves, because of limited foraging opportunities during reproduction. Others may be able to continue foraging during reproduction, thus relying on reserves to a lesser extent. We therefore predicted that, if male tactics involve such divergent limitations and trade‐offs within a species, ARTs should correspondingly differ in energy reserve allocation and utilization. To test this prediction, we studied short‐term and long‐term reserve storage patterns of males in the shell‐brooding cichlid Lamprologus callipterus. In this species, bourgeois males investing in territory defense, courtship, and guarding of broods coexist with two distinct parasitic male tactics: (1) opportunistic sneaker males attempting to fertilize eggs by releasing sperm into the shell opening when a female is spawning; and (2) specialized dwarf males attempting to enter the shell past the spawning female to fertilize eggs from inside the shell. Sneaker males differed from other male types by showing the highest amount of accumulated short‐term and long‐term fat stores, apparently anticipating their upcoming adoption of the nest male status. In contrast, nest males depleted previously accumulated energy reserves with increasing nest holding period, as they invest heavily into costly reproductive behaviors while not taking up any food. This conforms to a capital breeder strategy. Dwarf males did not accumulate long‐term fat stores at all, which they can afford due to their small behavioral effort during reproduction and their continued feeding activity, conforming to an income breeder strategy. Our data confirm that the resource storage patterns of males pursuing ARTs can diverge substantially, which adds to our understanding of the coexistence and maintenance of alternative reproductive patterns within species.     

Linking alternative reproductive tactics and habitat selection in Northern chamois

In polygynous ungulates, males may achieve fertilization through the use of alternative reproductive tactics (ARTs), discrete phenotypic variations evolved to maximize fitness. ARTs are often associated with different male spatial strategies during the rut, from territoriality to female‐following. Although variation in space use patterns of rutting male ungulates is known to be largely affected by the spatial distribution of females, information on the year‐round habitat selection of alternative reproductive types is scant. Here, we investigate the seasonal variation in habitat choice of a large mammal with ARTs (territoriality and nonterritoriality), the Northern chamois Rupicapra rupicapra. Global Positioning System (GPS) data on 28 adult males were collected between February 2010 and December 2013 in the Gran Paradiso National Park (Italy) and used to fit resource selection functions to explore the ART‐specific use of key topographic features, such as elevation, aspect, and slope, and vegetation phenology expressed as NDVI values. Territorial and nonterritorial chamois profoundly differed in their habitat selection not only during the rutting season. Compared to nonterritorial males, territorial males used lower elevations in summer and autumn, preferred southern slopes in spring and summer, and used steeper areas in summer but not in winter. We found no difference in seasonal selection of NDVI values between males adopting ARTs. Our results suggest that territorial males tend to occupy warmer, lower‐food‐quality habitats in late spring and summer, whereas nonterritorial males are free to follow and exploit vegetation phenology and more favorable temperatures. Different patterns of habitat selection may reflect different trade‐offs between the optimization of energy balances throughout the year and the increase of mating opportunities during the rut in males adopting alternative reproductive tactics.     

Correlates and Consequences of Dominance in a Social Rodent

In harem‐polygynous societies, body condition is often correlated with dominance rank. However, the consequences of dominance are less clear. High‐ranking males do not inevitably have the highest reproductive success, especially in systems where females mate with multiple males. In such societies, we expect male reproductive success to be more highly skewed than female reproductive success, but reproductive skew in females can still arise from rankings established within matrilineal societies. Dominance can also impact life‐history decisions by influencing dispersal patterns in yearlings. To better understand the function of dominance in harem‐polygynous societies, we studied the causes and consequences of dominance in yellow‐bellied marmots (Marmota flaviventris), a social rodent with skewed male reproductive success and female reproductive suppression. Specifically, we examined body condition as a predictor and the probability of breeding, number of offspring, and dispersal as outcomes of dominance. Additionally, we looked at variation in dominance between males and females and adults and yearlings, because marmots can engage in distinct interactions depending on the type of individuals involved. We found that marmots in better body condition have higher dominance rank than those in poorer condition. In addition, adults are dominant over yearlings. Within yearlings, dominance does not influence dispersal, but those in better body condition are less likely to disperse. Within all adults, individuals in better condition produce more offspring per year. Within adult males, more dominant males have greater reproductive success. Despite previous evidence of reproductive suppression in females, we found no effects of dominance rank on female reproductive success in the current study. The function of dominance in female marmots remains enigmatic.     

Intracolonial social distance, signaling modality and association choice in the greater sac-winged bat (Saccopteryx bilineata)

Understanding patterns and motivations for social spacing greatly illuminates the structure and internal dynamics of given groups or social systems. The highly social, polygynous greater sac-winged bat, Saccopteryx bilineata, represents an excellent model for social spacing analysis, since the choice of individual roost-sites within a day-roost constitutes an enduring, often repeated decision about relative proximity to conspecifics. Day-roost colonies consist of one or multiple harem groups, each with several females and a single male. Additionally, non-harem males without females may be present. A social-distance–time-budget metric revealed that harem males, females, and non-harem males differed significantly in their respective spatial associations while roosting. Harem males and females were most closely associated, with harem males located at the center of harems instead of at the borders. Non-harem males associated significantly closer with one another than with harem females that they were trying to access. The signaling modality mediating social interactions depended on the respective social distances between communicating bats. Our results suggest a concentric social organization based around harem males, which may select roost sites in closest possible proximity to females to enhance courtship signal strength. This constitutes an interesting deviation from the normative form of harem maintenance, patrolling borders, in mammals.     

Environmental and demographic drivers of male mating success vary across sequential reproductive episodes in a polygynous breeder

Ecological and social factors underpinning the inequality of male mating success in animal societies can be related to sex ratio, sexual conflict between breeders, effects of nonbreeders, resource dispersion, climatic conditions, and the various sequential stages of mating competition that constitute the sexual selection process. Here, we conducted an individual‐based study to investigate how local resource availability and demography interact with annual climate conditions to determine the degree of male mating inequality, and thus opportunity for sexual selection across two sequential reproductive episodes (harem and subsequent mate acquisition) in a naturally regulated (feral) horse population in Sable Island National Park Preserve, Canada. Using a 5‐year, spatially explicit, mark‐resight dataset and hierarchical mixed‐effects linear modeling, we evaluated the influence of adult sex ratio (ASR) on mating success and then tested for effects of freshwater availability, density, unpaired male abundance, and precipitation during each breeding season. Unpaired male abundance, freshwater availability, and ASR differed in their effects on male mating success according to year and selection episode. Opportunity for sexual selection in males associated with harem acquisition increased with ASR, and unpaired male abundance further explained weather‐related interannual variation after accounting for ASR. In contrast, once a harem was secured, ASR had little effect on male mating inequality in regard to acquiring additional females, while interannual variation in mating inequality increased with decreasing freshwater availability. Our findings show that local demography, resource availability, and weather effect opportunity for sexual selection in males differently depending on selection episode, and can attenuate or accentuate effects of ASR.     

Social network predicts loss of fertilizations in nesting males of a fish with alternative reproductive tactics

Alternative reproductive tactics (ARTs) evolve when there is strong intra-sexual competition between conspecifics for access to mates. Typically, larger “bourgeois” males reproduce by securing the access to reproductive resources while smaller “parasitic” males reproduce by stealing fertilizations from larger males. A number of factors can influence the reproductive success of each tactic, including intrinsic (e.g. size) and extrinsic (e.g. tactic relative frequency) variables. An example where plastic ARTs occur is the peacock blenny Salaria pavo, with large males reproducing by defending nests and attracting females (bourgeois tactic) and small males reproducing by achieving sneaked fertilizations (parasitic tactic). In this study, we conducted field observations on individually tagged animals to determine their social network and collected eggs from 11 nests to determine the fertilization success of each male tactic. Paternity estimates for 550 offspring indicated an average fertilization success for nest-holder males of 95%. Nest-holder male morphological traits and social network parameters were tested as predictors of fertilization success, but only the number of sneakers present in the nest-holder’s social networks was found to be a predictor of paternity loss. Although male morphological traits had been previously found to be strongly correlated with reproductive success of nest-holder males, as measured by the number of eggs collected in the male’s nest, no correlation was found between any of the measured morphological traits and fertilization success for these males. The results suggest a stronger influence of the social environment than of morphological variables in the proportion of lost fertilizations by nest-holder males of this species.     

Female survival,lifetime reproductive success and mating status in a passerine bird

In facultatively polygynous birds, secondary females of polygynously mated males typically have reduced annual reproductive success, because polygynous males provide less paternal care than monogamous males. Life history theory predicts that, as a result of increased reproductive investment, secondary females should suffer from reduced survival and lifetime reproductive success, but previous studies provided only weak support for this hypothesis. We used 7 years of data to study the fitness of female collared flycatchers Ficedula albicollis in relation to mating status by estimating survival and lifetime reproductive success. Taking differences in recapture probability into account, a mark-recapture analysis revealed that females observed at least once to breed as secondary female had higher survival than other females. This relationship was not confounded by laying date, because when we assessed the impact of laying date on survival, we found similar survival patterns. Females of polygynous males had reduced breeding success in terms of number of young fledged during the current reproductive event. However, during their lifetime females found at least once in primary or secondary mating status produced significantly more eggs, and at least the same number of fledglings and recruits as monogamous females. Thus, in the collared flycatcher, females of polygynously mated males seem to suffer from mating status during the most recent reproductive event, but considering survival and lifetime reproductive success, the apparently disadvantageous mating event is not necessarily associated with reduced residual reproductive value.     

Determinants and long‐term costs of early reproduction in males of a long‐lived polygynous mammal

In long‐lived polygynous species, male reproductive success is often monopolized by a few mature dominant individuals. Young males are generally too small to be dominant and may employ alternative tactics; however, little is known about the determinants of reproductive success for young males. Understanding the causes and consequences of variability in early reproductive success may be crucial to assess the strength of sexual selection and possible long‐term trade‐offs among life‐history traits. Selective pressures driven by fluctuating environmental conditions may depend on age class. We evaluated the determinants of reproduction in male bighorn sheep (Ovis canadensis) aged 2–4 years using 30 years of individual‐level data. These young males cannot defend estrous ewes and use alternative mating tactics. We also investigated how the age of first detected reproduction was correlated to lifetime reproductive success and longevity. We found that reproductive success of males aged 3 years was positively correlated to body mass, to the proportion of males aged 2–4 years in the competitor pool, and to the number of females available per adult male. These results suggest that reproductive success depends on both competitive ability and population age–sex structure. None of these variables, however, had significant effects on the reproductive success of males aged 2 or 4 years. Known reproduction before the age of five increased lifetime reproductive success but decreased longevity, suggesting a long‐term survival cost of early reproduction. Our analyses reveal that both individual‐level phenotypic and population‐level demographic variables influence reproductive success by young males and provide a rare assessment of fitness trade‐offs in wild polygynous males.     

Relative fitness of alternative male reproductive tactics in a mammal varies between years

1. In many species, males can use different behavioural tactics to achieve fertilization, so-called alternative reproductive tactics (ARTs). Few field studies have measured fitness consequences of ARTs under varying environmental conditions. 2. Here, we describe fitness consequences of three phenotypically plastic ARTs in the African striped mouse (Rhabdomys pumilio) and show that relative fitness of ARTs differs between years. Each year represents a different generation. 3. For the generation living under high population density, tactics differed in relative fitness in accordance with the theory of conditional strategies, with highly successful territorial breeding males having 10 times higher success than solitary roaming males and 102 times higher success than adult natally philopatric males. 4. For the generation living under intermediate population density, the territorial breeding and roaming tactics yielded similar fitness, which would be in agreement with the theory of mixed strategies. No philopatric males occurred. 5. For the generation living under low population density, roaming was the only tactic used and some roamers had very high fitness. 6. The main prediction of status-dependent selection for conditional strategies is a correlation between fitness and status, often measured as body mass, but we did not find this correlation within tactics when more than one tactic was expressed in the population. 7. Female distribution seems to have an effect on which reproductive tactics male chose: female defence polygyny when females are clumped (interference competition), but a searching tactic when females are dispersed (scramble competition). In contrast to predictions arising from theory on scramble competition, male body mass was important in determining fitness only in the year when females were dispersed, but not in other years. 8. Our results indicate that the differentiation between conditional and mixed strategies is not an absolute one. In many other species, environmental conditions might fluctuate temporally and spatially so that the normally suboptimal tactic yields similar fitness to the (usually) dominant tactic or that only a single tactic prevails. 9. We suggest the term single strategy, independent of current fitness consequences, for systems where tactics are not genetically determined, in contrast to genetically determined alternative strategies.     

Impact of male alternative reproductive tactics on female costs of sexual conflict under variation in operational sex ratio and population density

Sexual conflict over mating rate is both pervasive and evolutionarily costly. For females, the lifetime reproductive fitness costs that arise through interactions with potential mates will be influenced by the frequency of such interactions, and the fitness cost of each interaction. Both of these factors are likely to be influenced by variation in operational sex ratio (OSR) and population density. Variation in OSR‐ and density‐dependent male alternative reproductive tactics (ARTs) may be particularly important if the fitness costs that females experience vary with the reproductive tactics that males express. Using a simple model, we consider several examples of OSR‐ and/or density‐dependent variation in male ARTs and the frequency of male–female interactions, and find that variation in the expression of male ARTs has the potential to augment or diminish the costs of frequent male interactions for females. Accurately documenting variation in the expression of male ARTs and associated female fitness costs will benefit future work in this area.