Mating Tactics Research Articles

Female mating tactics in lekking fallow deer (Dama dama): experience explains inter-individual variability more than costs

Most studies on ungulate reproduction have focused on the covariates of male reproductive success, while there is much less information on female tactics of mate choice. The aim of this work is to fill this gap and to assess condition-dependent variations in female tactics in a lekking fallow deer (Dama dama) population. In particular, we investigated three indirect selection mechanisms: i) aggregation: when females join an already formed female group; ii) copying: when females copy the mate choice of other females and iii) territory choice: when females select a territory where many copulations had previously occurred. Our results show that female fallow deer, which are less experienced (younger) and/or incur higher travel costs (home range far from the lek), adopt indirect forms of mate selection more often than older females or females residing near the lek, respectively. Compared to adults, younger females remained longer in the lek (almost three times) and in male territories, returning to the lek after copulation. However, despite the time spent at the lek, younger females were not able to select the highest-rank males, and relied on territory choice more often than older females. Farther does visited the lek less frequently (farthest females only once) and arrived on average 5 days later than closer females (which performed up to 7 visits), but they were seen more often within female groups (aggregation). We did not find a different amount of copying in younger or in farther females. Our results contribute to advance our understanding of female behaviours in ungulate leks.

Multilevel societies facilitate infanticide avoidance through increased extrapair matings

In mammals characterized by a mating system in which a single male monopolizes reproduction, infanticide is reported to occur following a male take-over, often resulting in females returning to oestrus more rapidly than if their infant has survived. However, over the course of a 17-year study of golden snub-nosed monkeys, Rhinopithecus roxellana, a polygynous colobine species, we found no behavioural or suspected evidence of infanticide. Based on social network and genetic analyses, we found that more than half of the infants were sired as a result of extrapair matings (EPMs). Female golden snub-nosed monkeys initiated EPMs with bachelor or neighbouring resident males. These were considered ‘sneaky’ copulations because they did not occur in the presence of the leader male of the female's one-male unit (OMU). We suggest that through a process of paternity confusion, females decreased the likelihood of infanticide after a male take-over. In contrast, in a group of the same species in which the number of bachelor males was artificially reduced, EPMs were infrequent and four cases of infanticide were observed, three of them following a male take-over. Golden snub-nosed monkeys reside in a large multilevel society that develops by the fusion of several independent OMUs to form a breeding band, which is characterized by increased social cohesion and intrasexual tolerance among leader males. Females play an active role in mate choice, and engage in a diverse set of mating tactics, including counterstrategies such as EPMs to avoid infanticide. These results offer new insights into the diversity of behavioural strategies facilitated by complex social structures in nonhuman primates, as well as other social mammals.

Going beyond conventional parameters to unveil sperm quality in fish: the use of fibre optic technology to assess mitochondrial respiratory performance.

ABSTRACTSperm fertilisation success depends on both intrinsic quality and the interactions with the surrounding reproductive fluids. In several fish species, these interactions have a variable effect on sperm performance. Although specific responses to reproductive fluids may depend on intrinsic differences in sperm quality, variations in the traditionally recorded sperm functional traits do not fully account for the observed patterns. New methods to enhance the evaluation of sperm quality may prove to be valuable at both applied and theoretical levels, by improving the breeding protocol of reared species and the understanding of mating success in sperm competition contexts. Here we develop a fibre optic-based technique, also adequate for small ejaculate samples, to test the role of mitochondrial respiratory efficiency in deciphering sperm performance variability. We purposely used as model the grass goby, Zosterisessor ophiocephalus, a fish with guard-sneaker mating tactics where the sperm in each male tactic have similar intrinsic qualities (velocity, viability, ATP content), but sneakers' sperm exploit territorial males' seminal fuid, overall displaying better fertilization ability. We found that sperm differed in their mitochondrial respiratory efficiency, which was higher in sneakers’ sperm compared to territorial ones. This result draws the attention to an indicator of sperm quality that might be helpful in disentangling the mechanisms driving sperm-reproductive fluid interactions.

Alternative mating tactics in a cannibalistic widow spider: do males prefer the safer option?

Mating generally occurs with adult females, which undergo a suite of changes in morphology, physiology and behaviour during maturation. In the brown widow spider, Latrodectus geometricus, however, males can mate with immature females during a short period before they moult to the adult stage. Mating with immature females seems beneficial for males, because they are not at risk of being cannibalized, whereas cannibalism inevitably occurs in matings with adult females. We conducted choice experiments to elucidate male preference, courtship and mating behaviour with immature and adult females of different ages. We controlled for age of the females’ webs to provide males with potential web-borne attractants of similar age. We tested whether males distinguish immature females that are ready to mate (late subadult stage) from adult females and from immature females that do not mate (early subadults), and we examined male response to young versus old adult females. Males approached and mated with adult females more frequently than late subadult females, but there were no differences in the frequencies of approach to early and late subadults or to adult females of different ages. Once on the web, however, males attempted to mate with the late subadults. We suggest that web-borne volatile cues, typical of adult females, may be reduced or lacking in late subadult females, yet less volatile cues may indicate receptivity.

Novel ablation technique shows no sperm priming response by male eastern mosquitofish to cues of female availability

Changes in mate availability and sperm competition should generate selection to adjust investments into different pre- and post-copulatory traits so that the product of mating and fertilization success maximize net male reproductive success. Given costly sperm production and the risk of sperm depletion, males should invest strategically in ejaculates. Here, we use the eastern mosquitofish (Gambusia holbrooki), where males have a single coercive mating tactic, to test whether the number of cues indicative of female availability affects the rate of sperm available for mating (so-called sperm priming). We also tested whether plasticity in sperm production varies with male body size. We created four socio-sexual treatments that differ in the number of female-derived cues: none, chemical, chemical and visual, and full access to a female. We used ablation surgery, removing the tip of the male gonopodium (intromittent organ), to prevent males from mating with a female in the treatment where they interacted with females. We hypothesized that elevated sperm priming would be associated with more cues about female availability, and be more apparent in smaller, subordinate males due to their lower baseline sperm count (higher risk of sperm depletion) and their potential disadvantage during premating competition (leading to higher marginal benefits from sperm investment). There was, however, no evidence for sperm priming. The rate of sperm availability for mating and the baseline sperm reserves were, however, dependent on male body size. We discuss possible reasons for our findings. We also note that our study provides novel insights into the proximate mechanisms associated with sperm release in Poeciliids. Our confirmation of the fact that removing the gonopodium tip prevents a male from releasing sperm when housed with a female has many potential applications (e.g., in the study of effects of ejaculate investment and mating effort on male mating success and longevity). When ejaculates are energetically costly, males should strategically adjust sperm production in response to relevant social cues such as female availability. Using four socio-sexual scenarios, we demonstrate that male mosquitofish G. holbrooki do not produce less sperm when housed alone, compared to being exposed only to chemical cues from females, or to chemical and visual cues, or even when allowed full access to a female. The absence of plasticity in sperm production, when compared to that reported in other Poeciliid fishes, suggests that the relationship between sperm number and mating success might depend upon the mating system. If increased sperm number has a small effect on male reproductive success, there might not be selection for plastic shifts in sperm production. We also showed that ablation surgery on the male’s gonopodium allows us to let males interact with females without ejaculating.

Exposure to predator models during the fertile period leads to higher levels of extra-pair paternity in blue tits.

The perceived risk of predation can affect breeding behaviour and reduce reproductive success in prey species. Individuals exposed to predators may also adopt different mating tactics with potential consequences for the distribution of paternity in socially monogamous species that engage in extra-pair copulations. We experimentally increased perceived predation risk during the fertile period in blue tits Cyanistes caeruleus. Every morning between nest completion and the onset of egg laying, we presented a model of either a predator or a non-predator (control) near active nestboxes. Broods from pairs exposed to predators had higher levels of extra-pair paternity than control broods. This mainly resulted from a higher proportion of extra-pair offspring in broods with at least one extra-pair young. Females exposed to predators first emerged from the nestbox later in the morning, stayed away from the nestbox for longer and were less likely to be visited at the nest by their social mate, but we detected no behavioural differences once the model was removed. Our results suggest that the higher rates of extra-pair paternity resulted from the disruption of morning routines, which may have inhibited within-pair copulations or increased opportunities for females to engage in extra-pair copulations. We conclude that the perceived risk of predation can have substantial effects on levels of extra-pair paternity.

Nuptial feeding and genital coupling of Neopanorpa scorpionflies (Insecta: Mecoptera: Panorpidae) with notal organs of various lengths

Neopanorpa, the second largest genus in Panorpidae, is mainly characterized by the well-developed notal organ on male tergum III. However, it remains largely unknown how the length of the notal organ influences the nuptial feeding behaviour of Neopanorpa. Here, we investigated the nuptial feeding by comparing the morphology of mating-related structures and the genital coupling of a) Neopanorpa lui Chou & Ran, 1981 with a weakly-developed notal organ, b) N. carpenteri Cheng, 1957 with a medium-sized notal organ, and c) N. longiprocessa Hua & Chou, 1997 with an extremely elongated notal organ. The couples of N. lui and N. carpenteri maintain an intermittent mouth-to-mouth mode but do not exchange any edible food. After that the males secrete a salivary mass onto the surface as a nuptial gift, which is distinctly larger in N. carpenteri than in N. lui. Correspondingly, the male salivary glands are more developed in N. carpenteri than in N. lui. Males of N. longiprocessa bear very short salivary glands corresponding to a coercive mating tactic. The genital couplings are similar among the three species of Neopanorpa. The paired hypovalves of males are used to control the cerci of females. The prominent basal processes of male gonostyli grasp the posterior portion of the female medigynium across the intersegmental membrane. The male aedeagus physically couples with the female medigynium to ensure the male phallotreme to connect to the female copulatory pore. The influence of the notal organ length on the nuptial feeding behaviour of Neopanorpa is briefly discussed.

Tactical Tentacles: New Insights on the Processes of Sexual Selection Among the Cephalopoda.

The cephalopods (Mollusca: Cephalopoda) are an exceptional class among the invertebrates, characterised by the advanced development of their conditional learning abilities, long-term memories, capacity for rapid colour change and extremely adaptable hydrostatic skeletons. These traits enable cephalopods to occupy diverse marine ecological niches, become successful predators, employ sophisticated predator avoidance behaviours and have complex intraspecific interactions. Where studied, observations of cephalopod mating systems have revealed detailed insights to the life histories and behavioural ecologies of these animals. The reproductive biology of cephalopods is typified by high levels of both male and female promiscuity, alternative mating tactics, long-term sperm storage prior to spawning, and the capacity for intricate visual displays and/or use of a distinct sensory ecology. This review summarises the current understanding of cephalopod reproductive biology, and where investigated, how both pre-copulatory behaviours and post-copulatory fertilisation patterns can influence the processes of sexual selection. Overall, it is concluded that sperm competition and possibly cryptic female choice are likely to be critical determinants of which individuals' alleles get transferred to subsequent generations in cephalopod mating systems. Additionally, it is emphasised that the optimisation of offspring quality and/or fertilisation bias to genetically compatible males are necessary drivers for the proliferation of polyandry observed among cephalopods, and potential methods for testing these hypotheses are proposed within the conclusion of this review. Further gaps within the current knowledge of how sexual selection operates in this group are also highlighted, in the hopes of prompting new directions for research of the distinctive mating systems in this unique lineage.

Old females rarely mate with old males in roe deer, Capreolus capreolus

Abstract Little is known about whether female mating tactics vary with age based on their preference for mates. To fill this knowledge gap, we examined how maternal age is related to the age of their mates using detailed individual long-term monitoring of a genotyped and pedigreed European roe deer (Capreolus capreolus Linnaeus, 1758) population. We found that mating between old females and prime-aged males was more frequent than mating between prime-aged females and prime-aged males. This suggests that old females avoid old mates. Old females might be more selective in their mate choice than prime-aged females owing to increased mate-sampling effort. Our finding is in line with the terminal investment/allocation hypothesis. The study of age-related variation in female mating behaviour is particularly important because this behaviour can influence the intensity and direction of sexual selection and the maintenance of variation in male sexually selected traits. Further studies are needed to quantify the exact fitness benefits of age-specific mating tactics in females.

On the discovery of a male morph with a novelty alternative mating tactic in the neotropical cricket Macroanaxipha macilenta Orthoptera: Gryllidae)

Several animal taxa exhibit discrete male phenotypes, which are related to alternative mating tactics. In this study, we describe a new male phenotype and mating behavior of the cricket species Macroanaxipha macilenta. The most common male phenotype shows male-biased sexual size dimorphism, with wider forewings than those of the new male phenotype. Wide-forewing males produce longer and louder calling songs than narrow-forewing males, and after attracting a female, the wide-forewing male transfers a spermatophore during a 21-s copulation. On the other hand, narrow-forewing males occur at a low frequency in the population (< 20%), produce short whisper calls, and copulate twice with the female. In each copulation, the narrow-forewing male transfers one spermatophore. The first one is removed and eaten by the female shortly after copulation. Then, if the female stays near the male, they copulate again, and a second spermatophore is transferred to the females’ genitalia. Mating duration in narrow-forewing males can last up to 12 min. Both male morphs may represent alternative mating tactics.

Interplay between paternal germline and maternal effects in shaping development: The overlooked importance of behavioural ecology

Abstract Environmental conditions can have a lasting epigenetic impact on development, and there is increasing evidence that these effects can be transmitted across generations. Evidence for parental transmission of epigenetic variation to offspring has been primarily focused on paternal epigenetic influences induced by a male's experience of nutritional, social and toxicological exposures. There is an assumption in the literature that paternal influence on offspring in non‐biparental species is mediated exclusively through epigenetic transmission via the germline. However, integration of concepts from behavioural ecology into the study of parental transmission of environmental effects reveals the importance of mating tactics and maternal–paternal interplay in shaping resource allocation towards offspring in considering the mechanism(s) of epigenetic transmission. This paper describes the current state of knowledge regarding paternal epigenetic germline effects, the interplay between maternal and paternal influences and the importance of considering the complex nature of reproduction when predicting the transmission of phenotype across generations. Further, this paper highlights how incorporating concepts from behavioural ecology into the study of epigenetic transmission can refine predictions of phenotypes that emerge and create a more integrated notion of development and inheritance. It is proposed that theoretical and methodological approaches that consider the impact of reproductive context, which include mating dynamics, fertility, variation in parental life history and assessment of maternal effects, could improve the predictions made within studies of paternal epigenetic effects on offspring development. A free Plain Language Summary can be found within the Supporting Information of this article.

Size‐dependent investment in tusk length, testis size and sperm length in a biparental geotrupid beetle

AbstractMales of extreme small or large sizes often experience different levels of pre‐ and postcopulatory sexual selection that result in alternative ways to gain fertilization success. Here, we investigated such alternative mating tactics in Lethrus apterus, a biparental geotrupid beetle species with noticeable intermale size variation by comparing tusk (mandibular process) length, testis size and sperm length between large and small males. Firstly, we demonstrated evidence for male polymorphism as extremely large males had longer tusks relative to their body size than extremely small individuals. Secondly, large males had bigger testes than small males throughout the breeding season, however, a significant decrease was observed over time in large but not in small individuals. Thirdly, sperm length did not differ between the two size categories. Although these results do not explain how the observed large body size variation can be maintained in L. apterus, the non allometric relationship found between tusk length and body size and the lower decrease in testis size over the breeding season in case of small individuals might refer to the presence of alternative mating tactics in this species.

Aggression, color signaling, and performance of the male color morphs of a Brazilian lizard (Tropidurus semitaeniatus)

Behavior can help to establish dominance in intrasexual interactions, preventing more costly aggressive interactions and improving access to mates. Distinct color morphs often correlate with behavior, driving differential reproductive success between them. The lizard Tropidurus semitaeniatus usually expresses two male color morphs, Yellow or Black. It is likely that morphs play a role in reproduction, which is still unexplored. Here, we test whether there is morph-related dominance during intrasexual interactions. We used ex situ behavioral trials to test whether a particular morph shows dominance, gathering dominance by attributing scores to aggressive/evasive behaviors. We also tested whether winner individuals show higher performance (sprint speed), and whether spectrophotometric measures of body coloration predict winners of male encounters. Morphs showed differences in behaviors suggesting alternative behavioral tactics: Black males behave more aggressively and less evasively while Yellow males show the opposite sets of behavior. Black males also tend to be dominant, but dominants do not show higher sprint speeds than submissive males. Chest coloration, often displayed during encounters, highly predicts winnings (particularly high yellow chroma and low lightness and UV). Our results show that lizards signal competitive condition by behaviorally exposing their chest. Males displaying more head bobs and with darker chests are more likely to win encounters. Our results suggest that Yellow males might undertake a sneaker tactic, preventing aggression costs by evasiveness even though they might perform similarly to Black males. Further studies should address whether female preference is biased in relation to male morphs and its colorations, which would suggest selective processes towards costly signals and morph maintenance. In the struggle for survival and reproduction, often, there is no single best strategy and multiple distinct tactics may evolve. Behavior, color signaling, and performance are frequently correlated with distinct color morphs, which can coexist as alternative mating tactics. However, studies that are able to integrate all these traits are scarce. Here, we test whether different color morphs of the lizard Tropidurus semitaeniatus show different behaviors and dominance patterns. We also test whether these color morphs differ in their performances (sprint speed) and visual signaling (behavioral displays and intensity of coloration). We demonstrate that Black and Yellow-morph males adopt distinct behavioral tactics: an aggressive (Black-morph) and an evasive (Yellow-morph) tactic. We also show that dominance is highly correlated to chest’s intensity of dark yellow colorations and that lizards signal their dominance status through displays of head bob bouts.

Nutrition during sexual maturation and at the time of mating affects mating behaviour in both sexes of a burying beetle

Theory predicts that the outcome of mating interactions should be influenced by the condition of both males and females. First, females should base their mating decisions on reliable cues about male quality, which are often condition dependent. Second, the costs and/or benefits of being choosy during mating may depend on the female's own condition. Finally, when males divide their time between different mating tactics, investment in alternative mating tactics may depend on male condition. Here we examined the effects of male and female nutritional condition on mating behaviour in the burying beetle Nicrophorus vespilloides. We manipulated male and female nutritional condition either during sexual maturation or at the time of mating and monitored female mate choice and male mating tactics. We found that females in poor condition (i.e. starved either during sexual maturation or at the time of mating) preferred to mate with males in good condition over males that were starved at the time of mating. In contrast, well-fed females showed no such preference. Furthermore, males that were starved during sexual maturation increased their investment in alternative mating tactics by spending more time signalling for females. Our results add to evidence suggesting that females in poor condition bias mating towards males in good condition although it is currently unclear why these females are choosier in this species. Ours is the first study to demonstrate that nutritional condition during sexual maturation can influence mating behaviour, which may have implications for the rate and direction of sexual selection.

Maintenance of deceptive gifts in a natural spider population: ecological and demographic factors

AbstractAlternative mating tactics are expected to occur predominantly when mate competition is intense, resources are in short supply, or as a result of asymmetric power relationships between individuals. Males of the nuptial gift-giving spider Pisaura mirabilis use a prevailing tactic of offering a nutritive gift (insect prey) and a deceptive tactic of offering a worthless gift (consumed prey) to prospective mates. If the male’s tactic depends on precopulatory male–male competition, worthless gifts should occur primarily late in the season, when the operational sex ratio (OSR) becomes male-biased. If it depends on resource availability and/or postcopulatory sexual selection (sperm competition), worthless gifts should occur mostly early in the mating season, when prey availability is low and most females are unmated (i.e., postcopulatory sexual selection is weak). Nuptial gift construction correlated positively with prey availability and negatively with OSR, suggesting that males increase reproductive effort when resource and mate availability increase. We did not find evidence for body condition affecting male tactic use. Male size had a marked effect on the reproductive tactic employed. Males that matured early in the season were very small and employed mostly the nutritive gift tactic during their short life. Among the males that matured later and persisted through the season, relatively small males employed the worthless gift tactic whereas large males employed the nutritive gift tactic. We suggest that the existence of 2 distinct life-history strategies among males (early small and late large size) interacts with environmental and demographic conditions to maintain the deceptive tactic.

Me against who? Male guppies adjust mating behaviour according to their rival’s presence and attractiveness

AbstractSexual selection theory suggests that males need to constantly reappraise their mating decisions to take account of the presence and the phenotypes of their rivals. Here we examine this expectation by asking: (i) If the presence of a rival influences male mating behaviour; (ii) How important is the attractiveness of the rival (absolute attractiveness) in shaping male behaviour; and (iii) How does a male's attractiveness in comparison to his rival (relative attractiveness) influence a male's mating decisions. Using the Trinidadian guppy, a species in which female mate choice (based on males’ attractive traits) plays an important role in male mating outcomes, we recorded the frequency of courtship displays and unsolicited attempts by focal males. First, we quantified focal male mating behaviour with and without a rival. Since the probability of a successful mating is, on average, halved by the presence of a rival, we predicted that under competition the focal male would invest more in less costly mating tactic—unsolicited attempts. Second, we examined how the rival's standard length and area of orange coloration mediated focal male mating behaviour. We found that rival presence influenced how focal males responded to females in terms of both mating tactics. However, the rival attractiveness elicited changes only in male courtship display. Focal males increased courtship display rate if his rival was small or if possessed large amounts of orange, regardless of considering rival absolute or relative attractiveness. Our results show that males invest in the costlier mating tactic when there is no rival or in the presence of a smaller rival. Interestingly, they make a similar investment in the presence of an attractive orange rival. Overall, this study highlights the importance of fine‐grained male decisions in mating encounters and shows that mating tactics are differentially shaped by multiple competition risk cues.

Testosterone-dependent facial and body traits predict men's sociosexual attitudes and behaviors.

Strategic Pluralism Theory contends that human mating strategies are calibrated toward short-term (ST) or long-term (LT) mating according to the expression of condition-dependent traits and characteristics of the social and physical environment. Traits reflecting the effects of testosterone have been considered condition-dependent traits that provide information about the calibration of male mating strategy. We investigated the relationship of muscle mass and facial masculinity with attitudes and behaviors reflecting ST and LT mating tactics. We measured skeletal muscle mass (SMM) through bioelectrical impedance and facial width-to-height ratio (fWHR) in a sample of Chilean men (n = 206; mean age = 22.52 ± 4.65 SD), and collected information about sociosexual attitudes and past sexual behavior. Our results showed an interaction effect of SMM and fWHR on unrestricted (but not restricted) sociosexual attitudes and past sexual behavior. Individuals with a consistent expression of both traits (ie, high SMM and fWHR or low SMM and fWHR) reported higher levels of unrestricted sociosexual attitudes and a greater number of lifetime and previous-year sexual partners. These findings suggest that the intensity and consistency of expression of body and facial masculinity is important in signaling male mating tactics and sociosexual attitudes.

Growth and reproductive characteristics of rarely observed resident female Dolly Varden (Salvelinus malma malma) in North America

Among North American populations of northern form Dolly Varden (Salvelinus malma malma) exhibiting partial migration, the resident female life history is rarely encountered. Between 2012 and 2016, three sexually mature females confirmed as residents using otolith strontium analysis were captured from three rivers in the western Canadian Arctic (< 1% of residents sampled). Size-at-capture and size-at-age, estimated using otolith back-calculation, were compared to resident males and anadromous females. Fecundity, egg diameter, and gonadosomatic index (GSI) were compared to anadromous female current-year spawners. Resident females (fork length range 220–360 mm) tended to be among the largest-sized residents (two were > 90th percentile). Early size-at-age of resident females either exceeded or were among the largest sizes compared to resident males and pre-smolt anadromous females. Residents had similar fecundity predicted for length and egg size (range 3.5–4.2 mm) compared to anadromous, although GSI (range 13.2–17.4%) was inconsistent among populations. Interestingly, one resident female attained a greater size-at-capture and fecundity than the smallest anadromous current-year spawner. Our results suggest that conditional mating tactics of Dolly Varden can be expressed by both sexes in multiple populations, and increases understanding of Dolly Varden life history diversity and bet-hedging strategies in partially migratory populations.

Alternative Mating Tactics in Socially Monogamous Prairie Voles, Microtus ochrogaster

ABSTRACT: Alternative mating tactics appear to evolve when sexual selection is strong. Because such conditions are usually observed in species with polygynous or polyandrous mating systems, alternative mating tactics in monogamous mating systems are seldom documented and are poorly understood. In prairie voles, Microtus ochrogaster, a species widely known for forming monogamous pair-bonds, the expression of territoriality within each sex is dimorphic, and includes non-territorial “wanderers” as well as territorial “residents.” To explore the variance in fitness, measured in offspring numbers, among breeding individuals expressing these alternative mating tactics, we compiled parentage data over three years for male and female prairie voles from natural populations in Indiana and Kansas, USA. We found that: (1) the average fitnesses of males and females within each population were identical when adjusted by the sex ratio; (2) the variance in fitness in male and female prairie voles was comparable to that of many highly polygynous species; (3) The average fitnesses of male tactics, and of female tactics, were equivalent within and among years within each location; (4) consistent with negative frequency-dependent selection acting on mating phenotypes, the between-tactic variance in fitness for male and female mating tactics decreased with increasing study duration; (5) consistent with negative assortative mating, resident males and wanderer females produced offspring primarily in monogamous partnerships, whereas wanderer males and resident females produced offspring primarily in polygamous partnerships. Our results show that the conditions necessary for the persistence of alternative mating tactics are indistinguishable from those for phenotypically less flexible alternative mating strategies, and that alternative mating tactics can evolve in both sexes in monogamous species when fitness variance within each sex is large.

Examining the 'cosmetics placebo effect'.

Previous studies have found a positive effect of cosmetics on certain behavioral measures, such as the tip given to waitresses by male patrons. These studies have employed confederates who usually wear cosmetics. We therefore sought to examine whether the positive effect found in these studies could, in part, be explained by a change in behavior. In order to test the possibility of a ‘cosmetics placebo effect’, we employed a confederate to solicit donations from passersby. On some days our confederate would not have any cosmetics applied to her face (i.e., no cosmetics condition), on some days cosmetics were pretended to be applied to her face (i.e., placebo cosmetics condition), and on other days cosmetics were actually applied to her face (i.e., cosmetics condition). In line with previous research, we found that across conditions men donated significantly more than women to our female solicitor, providing support for the ‘showoff hypothesis’, in which male generosity serves as a mating tactic. When investigating men’s donations in more detail, we found that the highest percentage of donations came in the cosmetics condition, followed by the placebo cosmetics condition, and then by no cosmetics condition. The effect of condition on donation rates, however, was not statistically significant. Our study was limited to one solicitor and one dependent variable (i.e., percentage of people approached who donated) and therefore future research would benefit from using more confederates as well as examining other behavioral measures. Given the influence of cosmetics use on so many real-world outcomes, we believe that further exploration into a possible ‘cosmetics placebo effect’ would be valuable.