Male Mating Effort Research Articles

Strategic male mating effort and cryptic male choice in a scorpionfly.

In animal species with high male mating effort, males often find themselves in a dilemma: by increasing their mating effort, the gain from each copulation increases but simultaneously reduces available resources and, thus, the opportunity for future copulations. Therefore, we expect males to spend less reproductive resources on matings that provide low reproductive potential, thereby saving resources for future copulations, possibly with high-quality females, a sort of cryptic male choice. However, the strength of the trade-off between investment in a current mating and resources available for future matings must not be the same for all males. Males with relatively high mating costs should allocate their limited resources more cautiously than males with more plentiful resources. Here, we examine this prediction in the scorpionfly Panorpa cognata. Prior to copulation, males produce a large salivary mass on which females feed during copulation. We show that the production of larger salivary masses leads to longer copulations. Moreover, the size of the salivary gland and salivary mass increases with increasing male condition. However, males in poor condition make a relatively higher mating investment than males in good condition. We therefore expect male condition to influence cryptic male choice. In accordance with our hypothesis, only males in poor condition choose cryptically, producing larger salivary masses in copulations with females of high fecundity.

Male care and mating effort among Hadza foragers

Paternal care figures prominently in many scenarios of human evolution. Recently, however, such scenarios have been challenged on two scores. First, the level of male contribution may be insignificant. Second, male care may be provided as a form of mating effort, rather than parenting effort. In theory, since men can enhance their Darwinian fitness both by providing care to their own offspring if this raises offspring fitness and by pursuing additional mates if this leads to additional offspring, men should respond to payoffs from both mating and parenting effort. If men respond to payoffs from parenting effort, paternity ought to make a difference. And if men respond to payoffs from mating effort, mating opportunities ought to make a difference. I analyzed the impact of these two factors on variation in male care among the Hadza, a foraging society in Tanzania. Two predictions were tested: (1) biological children will receive more care than stepchildren, and (2) men will provide less care to their biological children as their mating opportunities increase. Both predictions were supported. These results suggest men provide care, in part, as parenting effort, and that they trade off parenting effort for mating effort when they have greater mating opportunities.

SIZE, SYMMETRY, AND SEXUAL SELECTION IN THE HOUSEFLY, MUSCA DOMESTICA.

Relationships between measures of body size, asymmetry, courtship effort, and mating success were investigated in the housefly, Musca domestica (Diptera: Muscidae). A previous study indicated that both male and female flies with low fluctuating asymmetry enjoyed enhanced mating success. The aim of our investigations was to determine whether the greater success of symmetrical males is due to variation in male mating effort or to female choice and whether males exhibited mate choice. However, our study found directional rather than fluctuating asymmetry with both male and female flies having, on average, longer left wings than right. Also, asymmetry was not related to mating success in either sex. Rather, both males and females appeared to exhibit choice on the basis of the size of potential mates, with males preferring females with long bodies and females preferring heavy males. Possible benefits from choice of large mates are discussed. The initial mating strikes (in which the male leaps onto the back of the female) did not appear to be targeted according to female morphology, and their frequency did not vary according to male morphology. This indicates that mate choice by both sexes according to size probably occurs during the later stages of courtship, when the flies are in intimate contact. Possible reasons for the absence of choice according to asymmetry are discussed.

Competition for Mates in the Mole Salamander, Ambystoma Talpoideum: Tactics That May Maximize Male Mating Success

The relatively brief mating periods that are typical of mole salamanders (Amphibia: Caudata: Ambystomatidae) have surely selected for males that are efficient in locating and mating with females in the presence of high densities of competitors. We analyzed quantitatively the competitive mating tactics of the mole salamander, Ambystoma talpoideum, in two laboratory studies. First, we observed competitive interactions in encounters staged between two males and a single female. Such interactions were frequent, with males scrambling to interrupt one another's courtship efforts in an apparent attempt to 'steal' inseminations (and, we assume, fertilizations). The competitive behaviour patterns exhibited by male A. talpoideum appear typical of many other ambystomatid salamanders. We then conducted an experiment to determine the influence of a male-biased operational sex ratio on male mating effort (comparing the performance of target males placed with females alone and in the presence of three potential rivals). Contrary to our expectation, target males decreased their mating effort when density was high and the operational sex ratio was male-biased; many simply abandoned any attempt to court and mate. We hypothesize that decreased male mating effort under a currently male-biased operational sex ratio will be favoured if there exist alternative opportunities for relatively competition-free encounters with females. We suggest a method of testing this hypothesis using comparative data.

Testosterone and mate choice in the dark-eyed junco

Investigations of the effects of testosterone on male mating effort have focused on behaviours associated with intra-sexual interactions. We tested whether testosterone may also affect male reproductive behaviour by mediating the intensity and frequency of male courtship. In two simultaneous choice experiments, we assessed the relative attractiveness of testosterone-implanted males, whose testosterone levels were manipulated to match naturally occurring spring peaks, and empty-implanted control males, whose testosterone levels were lower and resembled those of males caring for young. In both experiments, testosterone-males outperformed control-males, giving both more frequent and more exaggerated displays. Females showed a significant preference for the peak-testosterone males as measured by both female attendance and female courtship displays. We concluded that variation in testosterone can affect male attractiveness to females and thus male copulatory success. Thus, testosterone has the potential to mediate all aspects of male reproductive behaviour and may provide a mechanism through which males adjust their full range of breeding behaviours (i.e. inter-sexual as well as intra-sexual and parental behaviour) to fit their current status. In a second experiment, we tested the effect of oestradiol treatment on female mating preferences. No evidence was found that oestradiol changed the preferences of females.

Male display rate reveals ejaculate characteristics in the Trinidadian guppy,Poecilia reticulata.

Previous work (Reynolds and Gross 1992) has demonstrated that mate choice enables female guppies, Poecilia reticulata , to obtain heritable benefits (‘good genes’) for their offspring. It is not yet known whether males also signal their functional fertility, that is, their viability as fathers, to female guppies. Our study tested the hypothesis that a male9s behaviour reveals characteristics of his ejaculate. We uncovered a strong correlation between display rate and sperm number in male guppies derived from two wild Trinidadian populations. This result indicates that information on the functional fertility of potential mates is available to females. However, our investigation also found a significant relationship between the frequency of sneaky mating and sperm number. Female guppies in wild populations, particularly those experiencing a high predation regime, are constantly subjected to sneaky mating attempts. As the males responsible for these sneaky matings have highest reserves of sperm they may have the capacity to undermine female choice. The implications of these findings for sperm competition are discussed.

Effect of male body size on sperm precedence in the polyandrous butterfly Pieris napi L. (Lepidoptera: Pieridae)

Male Lepidoptera produce an ejaculate during copulation that contain* both sperm and accessory gland nutrients and may function as paternal investment and/or male mating effort Several studies have examined how ejaculates function-as paternal investment, but few have determined the influence of sperm competition on male investment This study examines the effect of male body size on sperm precedence in the polyandrous butterfly Pitris napi L. We used male body mass as an indicator of die size of ejaculate transferred and found that relative male size had a significant effect on paternity. The offspring of twicemated females showed a low incidence of mixed paternity. Larger males obtained the majority of fertilizations, and the degree of second-male sperm precedence was influenced by relative body size of mating males. In general, second mates obtained fewer fertilizations the larger the size of the first mate. The interval between the first and second mating was influenced by the m* of the first male maty Females first mated to small males remated sooner than females first mated to large rPaW Our results suggest that large males may have a selective advantage over small males when both a male's fertilization success and a female's refractory period are influenced by the size of ejaculate transferred. Furthermore, the effect of male body size on the proportion of offspring sired lends support to the hypothesis that sperm competition has played a major role in the evolution of ejaculate size. Key words: body size, ejaculate size, maring frequency, Pitris napi, polyandry, sperm competition. [BAavEcol 8:511-523 (1997)]

Male-infant-male interactions in Tibetan macaques

Event-sampling and scans were used for collecting data on male-infant-male triadic interactions, and their effects on member spacing respectively in a group ofMacaca thibetana at Mt. Emei in 1989. The group was partially provisioned by human visitors in seasons other than winter, and could be observed closely. In addition, a stable linear male-hierarchy among five males existed for two years since the end of 1987, providing a good social condition for this topic. The triadic interactions were specific to the birth season, and recognized as three types being on a continuum functionally changing from passive “agonistic buffering” (4.8%) to active spatial cohesion, which resulted in a significant decline of intermale distances. Positive correlations were documented between the triad initiation rate and the number of females in consort with the males in the mating season (MS), and between the triad reception rate and the number of infants in proximity to the males in the MS when maternal care was significantly reduced. Thus the male's mating effort and kin/sexual selection may deeply be involved in the triad of this species. Considering that the two triad-species,M. sylvanus andM. thibetana, had different levels of paternity, but shared similar foraging conditions, and showed similar intensities of male-infant caretaking, the triad was very likely a by-product of male-infant caretaking, which was probably shaped to compensate heavy maternal investment to young offspring in harsh conditions. Accordingly, the long-term arguments about the triad inM. sylvanus can be united to a model of the way in which “male-infant caretaking” hypothesis works ultimately, and “regulating social relations” hypothesis does proximately.

Phenotypic engineering: using hormones to explore the mechanistic and functional bases of phenotypic variation in nature

Perhaps the best way to determine whether and how traits of organisms are currently adaptive is to alter them experimentally and compare the relative fitness of altered and unaltered individuals. We call this method phenotypic engineering. To the extent that natural selection moulds organisms on a trait‐by‐trait basis, we would expect fitness of unmanipulated (control) individuals to be higher than that of experimentally altered individuals. However, other outcomes are possible and of interest. If, for example, a single trait were altered and the fitness of manipulated and unmanipulated organisms were found to be similar, we might conclude that selection is not currently operating on the altered trait. Phenotypic engineering with hormones describes an experimental approach to the study of adaptive variation in suites of traits that are hormonally mediated and correlated in their expression. A likely outcome of such manipulations is that some traits would be altered so as to elevate fitness but that changes in other, correlated traits would lower fitness. If the net effect were to depress fitness, a process by which natural selection shapes and maintains organisms as integrated units would be demonstrated. We have employed this approach in studies of the Dark‐eyed Junco Junco hyemalis, a small passerine whose reproductive success varies with the abundance of nest predators. We treated males with testosterone, documented the phenotypic consequences and related these to various measures of fitness. Summarizing results to date: Behavioural comparison of males treated with testosterone (T‐males) and control males (C‐males) shows that T‐males sing more frequently, are less attentive to offspring, have larger home ranges and are more attractive to females. Physiologically, testosterone accelerates entry into breeding condition in spring (loss of winter lipid stores) and results in higher levels of corticosterone. If exposure to testosterone is prolonged beyond the breeding season, pre‐basic moult is delayed or prevented. We are currently comparing T‐ and C‐males with respect to corticosteroid binding proteins, sperm reserves, response to nestling vocalizations and neuroanatomy. The relationship between testosterone‐induced phenotypic variation and fitness is still under study. When treatment extends well beyond the breeding season, testosterone significantly reduces survivorship; otherwise it does not. With respect to apparent reproductive success (i.e. estimates of paternity that are not based on genetic analysis), more young leave the nests of C‐males than of T‐males, but treatment groups do not differ in the number of young that reach independence. Preliminary data on realized reproductive success (i.e. number of genetic offspring sired) suggest that production as the result of extra‐pair fertilizations is greater in T‐ than in C‐males but that T‐males lose paternity of more of the offspring of their social mates to other males. Continued investigation will, we hope, reveal the factors governing the trade‐offs between male mating effort and parental effort and between survival and current reproduction, as well as the frequency with which the typical phenotype outperforms one that has been experimentally altered.

The male's dilemma: Increased offspring production is more paternity to steal

Large potential effects of male care on the number of offspring females successfully raise are not sufficient to select for caring males because of the pervasive importance of mating competition. Males face a version of ‘the social dilemma’, in which increased production increases the pay-off for theft. Models of the allocation of male effort partitioned between caring for babies and competing for paternity show that the optimal allocation to care is very low under a wide range of conditions. Like sex allocation where the alternatives are male versus female function or sons versus daughters, the pay-offs to one alternative are always strongly frequency dependent. Because that alternative (male function, sons, male mating effort) pays so well when rare, it cannot remain rare under most conditions. Here we consider the consequences of partitioning mating effort into mate guarding and all other forms of mating conflict. If a male gets all his partner's conceptions while guarding, gaining them at a constant rate, there are two possible regions of stability. The evolutionarily stable strategy (ESS) depends on a parameter scaling the decisiveness of (non-guarding) mating conflict. When marginal returns from conflict decrease with scale, almost all effort goes into guarding. When marginal returns increase, the ESS devotes all effort to mating. Even when the potential effect of care is large, male equilibrium strategies allocate little effort to it. We also report the results of computer simulations showing that care increases if gains from guarding saturate quickly, so that a male is assured of the paternity of most of his partner's offspring with little guarding, and consequently the pool of unguarded conceptions open to competion shrinks sharply. But even when the male's dilemma is very much reduced, it still substantially limits the allocation to care. The results of both computer simulations and mathematical analysis converge with other lines of evidence that mating has much stronger effects than parenting in shaping male strategies.

Sex ratios, mating behavior and sexual size dimorphism of the northern water snake, Nerodia sipedon

Competition among males to mate is generally associated with male-biased size dimorphism. In this study we examine mating behavior in the northern water snake (Nerodia sipedon), a species in which males are much smaller than females despite substantial competition among males to mate. Competition among males was a consequence of a male-biased operational sex ratio due to slightly higher female mortality from a birth sex ratio of 1 : 1, and, in 1 year, more synchronous and longer mating activity by males. Approximately one-third of both males and females appeared not to mate in a given year. Larger males were generally more likely to attempt mating, but size did not explain the variance in the number of aggregations in which individual males participated. Within aggregations, males that were successful at achieving intromission were larger than unsuccessful males in 1 of 2 years. Variation in condition (mass relative to length) and relative tail length were not generally useful predictors of either mating effort or success in males. Because large size was often advantageous to males, sexual size dimorphism appeared not to be a consequence of sexual selection favoring smaller males. Because sexual dimorphism was evident at birth, and both males and females matured sexually at about 4 years, sexual dimorphism was not simply a consequence of one sex growing at the maximum rate for longer. Female fecundity increased with size, and sex differences in size-fecundity relations may underly the pattern of sexual size dimorphism. However, because multiple mating by females is common, sperm competition is likely to be important in determining male reproductive success. Therefore, allocation of energy to sperm rather than growth may also prove to be an important influence on male growth rates and sexual size dimorphism.

Why do male Callosobruchus maculatus beetles inseminate so many sperm?

Male Callosobruchus maculatus F. (Coleoptera: Bruchidae) inseminate more sperm than females can effectively store in their spermathecae. This study examines the adaptive significance of “excess” sperm transfer by measuring components of male and female reproductive success in response to manipulating the number of sperm inseminated. The number of sperm transferred during copulation was reduced from 56,000 ±4,462 to 8,700±1,194 by sequentially mating males to virgin females. Reducing the number of sperm inseminated by the first male to mate had no effect on the extent of sperm precedence, but reducing the number of sperm inseminated by the second male resulted in a significant reduction in the extent of sperm precedence. When large numbers of sperm are inseminated the remating refractory period of females is increased. These results indicate that males transferring large numbers of sperm during copulation have a two-fold advantage at fertilization; they are more effective at preempting previously stored sperm and they are likely to father more offspring by delaying the time of female remating. The transfer of “excess” sperm does not appear to serve as nonpromiscuous male mating effort; the number of eggs laid, their fertility and the subsequent survival of zygotes were unaffected by manipulating the number of sperm inseminated. The underlying mechanisms of sperm precedence were also examined. Simple models of sperm displacement failed to accurately predict the patterns of sperm precedence observed in this species. However, the results do not provide conclusive evidence against the models but rather serve to highlight our limited understanding of the movement of sperm within the female's reproductive tract.

Mating effort function of the spermatophore in the bushcricket Poecilimon veluchianus (Orthoptera, Phaneropteridae): support from a comparison of the mating behaviour of two subspecies

To analyse spcrmatophore function, various aspects of the mating behaviour (e.g. spermatophore mass, duration of sperm transfer, mating frequency) were compared in two subspecies of the bushcricket P. veluchianus. Body mass was significantly different in both subspecies and had a strong effect on spermatophore mass, resulting in a large difference in absolute and relative (percentage of male body mass) spermatophore mass in both subspecies. After copulation the small P. v. minor spermatophores were consumed much faster by the female than the larger ones of P. v. veluchianus. The time necessary for sperm transfer from the spermatophore to the female spermatheca was much shorter in the subspecies with small spermatophores than in that with large spermatophores, and in both subspecies similar to the time required to consume the spermatophores. Mating frequency varied also between the subspecies and was murh higher in P. v. minor than in P. v. veluchianus. Differences in body mass between the two subspecies therefore resulted in changes in several aspects of mating behaviour. However, despite large differences in the mass of the spermatophore, its main function seems to be to ensure sperm transfer. This can be concluded from the similarity between the duration of sperm transfer and the time period necessary for spermatophore consumption in each of the subspecies. The spermatophore is thus considered to be male mating effort.

Mating effort function of the spermatophore in the bushcricket Poecilimon veluchianus (Orthoptera, Phaneropteridae): support from a comparison of the mating behaviour of two subspecies

To analyse spermatophore function, various aspects of the mating behaviour (e.g. spermatophore mass, duration of sperm transfer, mating frequency) were compared in two subspecies of the bushcricket P. veluchianus. Body mass was significantly different in both subspecies and had a strong effect on spermatophore mass, resulting in a large difference in absolute and relative (percentage of male body mass) spermatophore mass in both subspecies. After copulation the small P. v. minor spermatophores were consumed much faster by the female than the larger ones of P. v. veluchianus. The time necessary for sperm transfer from the spermatophore to the female spermatheca was much shorter in the subspecies with small spermatophores than in that with large spermatophores, and in both subspecies similar to the time required to consume the spermatophores. Mating frequency varied also between the subspecies and was much higher in P. v. minor than in P. v. veluchianus. Differences in body mass between the two subspecies therefore resulted in changes in several aspects of mating behaviour. However, despite large differences in the mass of the spermatophore, its main function seems to be to ensure sperm transfer. This can be concluded from the similarity between the duration of sperm transfer and the time period necessary for spermatophore consumption in each of the subspecies. The spermatophore is thus considered to be male mating effort.

The association between rank, mating effort, and reproductive success in male Barbary macaques (Macaca sylvanus)

The association between social rank, mating effort, and reproductive success of male Barbary macaques (Macaca sylvanus) has been evaluated by longterm behavioral observations and subsequent paternity determination via oligonucleotide DNA fingerprinting in a large semifreeranging group. All offspring born between 1985 and 1988 that survived to at least 1 year of age (n=75) were available for paternity testing. The exclusion of all but one of the potential fathers from paternity was possible in 70 cases (93%). Mating activities were recorded using ad lib. and focal female sampling techniques. The analysis of male mating effort was restricted to the most likely days of conception. Male rank correlated significantly with male mating success in all four breeding seasons and with male reproductive success in three of the four seasons. Mating success and reproductive success also showed a significant correlation, with the exception of one breeding season, in which the proportion of males per fertilizable female was especially high. Poor mating success was almost always associated with poor reproductive success, while good mating success was less predictive for a male's actual reproductive success. This was apparently a consequence of sperm competition, resulting from the promiscuous mating system. Male mating success is not necessarily an unreliable indicator for reproductive success, provided that sufficient sample sizes are available and that conception periods can be determined. Sperm competition and other factors may weaken the association, however.

The Biology of a Subtropical Population ofHalictus ligatusSay (Hymenoptera; Halictidae)

AbstractIn the subtropical climate of the Florida Keys,Halictus ligatushas a continuously brooded, multivoltine colony cycle. This results in young gynes and workers being active at all times of year, potentially causing problems for males with respect to mate choice. Males responded to females by ignoring them, touching them briefly or by knocking them off of flowers into the surrounding vegetation, where mating takes place. Over half of the females at this locality are mated although males prefer large, young individuals. Multiple mating of females does occur. Males search for females around flowers and, less commonly, near nest sites. Because females of this social insect offer varied returns to male mating effort, it is not surprising that males exhibit mate choice.

Sexual Dimorphism in Bullfrogs

Data on body size, age/size at sexual maturity, and adult survival were obtained between 1975 and 1978 for a population of bullfrogs, Rana catesbeiana, at the E. S. George Reserve of the University of Michigan. Both males and females continued to grow when adults; older individuals were often 50% larger than newly matured individuals. No sexual differences in adult growth rate were observed, but data on average and maximum adult body size indicated that females were significantly larger than males during each year of the investigation. The discrepancy between these measures resulted from sex—specific differences in adult age distribution: males matured at earlier ages and/or smaller sizes than females, and large males suffered higher mortality than large females. Such life history differences between the sexes can in turn be related to patterns of mating effort and parental effort. Apparently, selection for mating effort in males to defend territories and parental effort in females to produce large clutches has resulted in sexual maturation at different ages but in similar advantages of large body size. The influence of mating effort and parental effort on sexual dimorphism is discussed for other anuran species as well as birds and mammals. It is suggested that an observed body size dimorphism in any species in which individuals grow appreciably as adults could result from a difference in the age distributions of males and females as well as from differential growth rates.

Cumulative Scaling of Paternalistic Behavior in Primates

Previous articleNext article No AccessNotes and CommentsCumulative Scaling of Paternalistic Behavior in PrimatesKevin B. BalesKevin B. Bales Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 116, Number 3Sep., 1980 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/283640 Views: 7Total views on this site Citations: 7Citations are reported from Crossref Copyright 1980 The University of ChicagoPDF download Crossref reports the following articles citing this article:Alice Baniel, Guy Cowlishaw, Elise Huchard Stability and strength of male-female associations in a promiscuous primate society, Behavioral Ecology and Sociobiology 70, no.55 (Mar 2016): 761–775.https://doi.org/10.1007/s00265-016-2100-8Patrick Ogola Onyango, Laurence R. Gesquiere, Jeanne Altmann, Susan C. Alberts Testosterone positively associated with both male mating effort and paternal behavior in savanna baboons (Papio cynocephalus), Hormones and Behavior 63, no.33 (Mar 2013): 430–436.https://doi.org/10.1016/j.yhbeh.2012.11.014Susan C. Alberts, Courtney L. Fitzpatrick Paternal care and the evolution of exaggerated sexual swellings in primates, Behavioral Ecology 23, no.44 (Jun 2012): 699–706.https://doi.org/10.1093/beheco/ars052S. Rosenbaum, J.B. Silk, T.S. Stoinski Male-immature relationships in multi-male groups of mountain gorillas (Gorilla beringei beringei), American Journal of Primatology 73, no.44 (Nov 2010): 356–365.https://doi.org/10.1002/ajp.20905Nga Nguyen, Russell C. Van Horn, Susan C. Alberts, Jeanne Altmann “Friendships” between new mothers and adult males: adaptive benefits and determinants in wild baboons (Papio cynocephalus), Behavioral Ecology and Sociobiology 63, no.99 (Jun 2009): 1331–1344.https://doi.org/10.1007/s00265-009-0786-6Carel P. van Schaik, Andreas Paul Male care in primates: does it ever reflect paternity?, Evolutionary Anthropology: Issues, News, and Reviews 5, no.55 (Jan 1996): 152–156.https://doi.org/10.1002/(SICI)1520-6505(1996)5:5<152::AID-EVAN3>3.0.CO;2-HCharles T. Snowdon, Stephen J. Suomi Paternal Behavior in Primates, (Jan 1982): 63–108.https://doi.org/10.1007/978-1-4613-3605-1_3