Vertical bars on male Xiphophorus multilineatus: a signal that deters rival males and attracts females

We examined the function of the vertical bar pattern on maleswordtails (Xiphophorus multilinneatus) as a signal in bothmale-male competition and female choice. This pattern had previouslybeen described as an aggressive signal because males intensifiedthe bars during male-male encounters in the laboratory. Ourfield observations supported this observation and also showedthat bars intensified when males courted females. The intensityof bars was correlated with access to females in the field.Within the size range of males that have bars, however, neitherbar number nor male size appeared to influence access to females.We used freeze-branding to remove the bars from males in thelaboratory so that we could control for characters correlatedwith bar intensity, and tested males and females separatelyso that we could separate the influence of these two componentsof sexual selection. We compared the responses of males andfemales to males that had their bars removed and control malesfreeze-branded between the bars. Test males responded more aggressivelyto males without bars as compared to control males. In addition,females showed a preference for control males over males thathad their bars removed. These results suggest that the barsmay function as a signal that deters rival males and attractsfemales.     

Ownership-dependent mating tactics of minor males of the beetle <Emphasis Type="Italic">Librodor japonicus</Emphasis> (Nitidulidae) with intra-sexual dimorphism of mandibles

Intra-sexual dimorphism is found in the weapons of many male beetles. Different behavioral tactics to access females between major and minor males, which adopt fighting and alternative tactics, respectively, are thought to maintain the male dimorphism. In these species major males have enlarged weapons that they use in fights with rival males. Minor males also have small weapons in some of these species, and it is unclear why these males possess weapons. We examined the hypothesis that minor males might adopt a fighting tactic when their status was relatively high in comparison with that of other males (e.g., ownership of a territory). We observed the behavioral tactics of major and minor males of the beetle Librodor japonicus, whose males have a dimorphism of their mandibles. Major males fought for resources, whereas minor males adopted two status-dependent tactics, fighting and sneaking, to access females, depending on their ownership of a sap site. We suggest that ownership status-dependent mating tactics in minor males may maintain the intra-sexual dimorphism in this beetle.     

Costs and benefits of variable breeding plumage in the red-backed fairy-wren

The red-backed fairy-wren is a socially monogamous passerine bird which exhibits two distinct types of breeding male, bright males that breed in bright red and black plumage and dull males that breed in dull brown plumage. Most males spend their first potential breeding season in dull plumage and subsequent breeding seasons in bright plumage, but a relatively small proportion of males develop bright plumage in their first breeding season. This study quantifies morphology, behavior, and reproductive success of dull and bright males to assess the adaptive costs and benefits of bright plumage while controlling for age. Older bright males (two years of age or older) attempted to increase their reproductive success via copulations with extrapair females, whereas younger (one-year old) bright males and dull males did not. Thus, older bright males spent less time on their own territories, intruded on neighboring groups with fertile females more frequently, gave more courtship displays, and had larger sperm storage organs than did younger bright males and dull males. Microsatellite analyses of paternity indicate that the red-backed fairy-wren has extremely high levels of sexual promiscuity, and that older bright males had higher within-brood paternity than dull males or younger bright males. Regardless of age, bright males were more attractive to females in controlled mate choice trials than were dull males, and both age classes of bright males obtained higher quality mates earlier in the breeding season than did dull males, when nesting success was higher. In conclusion, although it appears that bright plumage increases access to higher quality mates, age also plays a central role in determining a male's overall reproductive success because of the high levels of sexual promiscuity exhibited by the red-backed fairy-wren.     

Reduced Reproductive Success for a Conditioning Mutant in Experimental Populations of DROSOPHILA MELANOGASTER

Male Drosophila melanogaster that have courted newly-emerged males can modify their subsequent courtship behavior to avoid further courtship with immature males for up to 6 hr (previously reported). Here, it was hypothesized that such an experience-dependent modification would afford a mating advantage to normal males over males that carried a mutation that affects learning and memory. Coisogenic lines were constructed which varied at the dunce gene (dnc+ and dncM14 alleles) in order to test this hypothesis. Whether previously experienced with immature males or not, dnc+ and dncM14 males were indistinguishable in their response and mating efficiency when individually paired with virgin females. However, courtship performance of dnc+ and dncM14 males was different if they were first experienced with immature males and were then individually tested in an artificial population of nine immature males and one virgin female. In this situation, dnc+ males spent much less time in courtship with immature males and achieved copulation in one-third the time required for dncM14 males. As a control, the behavior and mating efficiency of courtship-naive dnc+ and dncM14 males in the artificial population was indistinguishable. In competition for a single virgin female, experienced dncM14 males showed a slight mating advantage over experienced dnc+ males. But when competition by experienced males for a single virgin female took place in the presence of nine immature males, dnc+ males were the successful maters in three-fourths of the trials.     

False promises: females spurn cheating males in a field cricket

Females commonly prefer to mate with males that provide greater material benefits, which they often select using correlated male signals. When females select higher-benefit males based on correlated signals, however, males can potentially deceive females by producing exaggerated signals of benefit quality. The handicap mechanism can prevent lower-quality males from producing exaggerated signals, but cannot prevent cheating by higher-quality males that choose to withhold the benefit, and this poses a major problem for the evolution of female choice based on direct benefits. In a field cricket, Gryllus lineaticeps, females receive seminal fluid products from males with preferred songs that increase their fecundity and lifespan. We tested the hypothesis that female behaviour penalizes males that provide lower-quality benefits. When females were paired with males that varied in benefit quality but had experimentally imposed average songs, they were less likely to re-mate with males that provided lower-quality benefits in the initial mating. This type of conditional female re-mating may be a widespread mechanism that penalizes males that cheat on direct benefits.     

The cost of peripheral males in a brook trout mating system

A focus on the reproductive contributions of males displaying alternative life histories has neglected the role of size-dependent peripheral males in salmonine mating systems. We documented mating behaviour of brook trout Salvelinus fontinalis, including observations of spawning, over two breeding seasons to determine the mating costs of peripheral males to dominant males (kleptogamy) and females (egg cannibalism). For males and females, the mating costs of peripheral males were substantial because more than half (56%) of all observed brook trout spawnings involved peripheral males. Males that paired with large females experienced a greater incidence of kleptogamy due to increased numbers of peripheral males present. Large males face a conflict when mating in that they prefer to spawn with large females; however, these same females attract numerous males against which the dominant male cannot defend. From paternity studies, we estimated that males that had peripheral males participate in spawning may fertilize, on average, equal numbers of eggs compared to males spawning solely with a smaller female. Females that paired with relatively smaller males had significantly more eggs eaten by peripheral males than females that paired with relatively larger males. Latency to spawn by females increased when paired with a relatively small male, and resulted in females obtaining a larger spawning partner. The observed patterns of size-assortative mating, kleptogamy and cannibalism are discussed in relation to mate choice for this population of brook trout. Copyright 1999 The Association for the Study of Animal Behaviour.     

Too big for his boots: Are social costs keeping condition‐dependent status signalling honest in an Australian lizard?

Australian painted dragon lizards Ctenophorus pictus occur in three head colours (red, orange and yellow) that differ in their level of aggression (reds being most aggressive), hormone profile (reds having higher testosterone levels) and in their frequency in our study population over time. They are also polymorphic in bib colour; some males have a bright yellow area under the chin, while others lack this coloured area entirely. We show that red males with a bib are in better body condition than red males that lack a bib. This contrasts sharply to yellow males, in which males with a bib are in poorer condition than yellow males that lack a bib. Our analysis also shows that following exposure to a high percentage of red (more aggressive) neighbours, all males suffer a reduction in body condition, and importantly, males with a bib (regardless of their head colour) suffer a more severe loss of body condition than males that lack a bib. Finally, this condition loss is significantly higher for yellow bibbed males than for red bibbed males, suggesting that the cost of sporting a bib may be higher for them. Orange males showed a non‐significant difference in condition between bib morphs. Our analysis also shows that bibbed yellow males (the morph with lower body condition), but no other morph category, declined significantly in their frequency between 2 years.     

Effect of auxiliary males on territory ownership in the oribi and the attributes of multimale groups

I observed free-ranging oribi, Ourebia ourebi, in Serengeti National Park, Tanzania, to determine whether group formation by males provides evidence for cooperative territory defence, a behaviour that is rare among male vertebrates. Socially dominant males that shared territories with subordinate auxiliary males were replaced by rivals less often than males that defended territories without auxiliary males. Auxiliary males marked territories with preorbital glands, dung and urine, and territories defended by male groups were marked more thoroughly than those defended by single males. Fifteen of 24 (62.5%) auxiliary males whose histories were known were born on territories defended by males that probably were their fathers. But 37.5% of auxiliary males probably were unrelated to dominant males, because male groups also formed when territory owners accepted adult male immigrants as subordinates, and when owners allowed young males to remain philopatric after evicting a male likely to have been the young male's father. All males in groups probably had some mating access to females, but dominant males may have minimized matings of auxiliary males by guarding fertile females. These results suggest that auxiliary male oribi aided dominant males in territory defence, and that dominants traded off the risks of losing matings to auxiliaries, or being overthrown by them, in exchange for a reduction in their chance of being evicted by rival neighbours or immigrants. Copyright 1999 The Association for the Study of Animal Behaviour.     

Description of alternative male reproductive tactics in a shell-brooding cichlid, Telmatochromis vittatus, in Lake Tanganyika

Telmatochromis vittatus (Cichlidae) is a Tanganyikan substrate brooder which spawns in the gastropod-shell nests of a cichlid, Lamprologus callipterus. We describe male reproductive tactics of T. vittatus in and around the shell nests, where males of various sizes were found. Based on utilization patterns of the shell nests, interactions among males, and spawning behaviors, males could be categorized into four types based on reproductive tactics and in order of body size: sneaker males, satellite males, territorial males and piracy males. Size range of males in tactic groups rarely overlapped. Territorial males defended shell nests harboring multiple females, but during pair-spawning they were occasionally taken over by large piracy males that visited several nests repeatedly. Small sneaker males darted to pair-spawning territorial males and might ejaculate sperm. Satellite males did not perform parasitic spawning but pair-spawned in a single shell outside the nests. Spawning of satellite males was infrequently parasitized. The largest gonado-somatic index (GSI) was found in sneaker males followed by piracy males, territorial males and satellite males, suggesting that gonadal investment of males using the four tactics may be consistent with intensity or risk of sperm competition.     

Diploid males sire triploid daughters and sons in the parasitoid wasp Cotesia vestalis

In the Hymenoptera, males develop as haploids from unfertilized eggs and females develop as diploids from fertilized eggs. In species with complementary sex determination (CSD), however, diploid males develop from zygotes that are homozygous at a highly polymorphic sex locus or loci. We investigated mating behavior and reproduction of diploid males of the parasitoid wasp Cotesia vestalis (C. plutellae), for which we recently demonstrated CSD. We show that the behavior of diploid males of C. vestalis is similar to that of haploid males, when measured as the proportion of males that display wing fanning, and the proportion of males that mount a female. Approximately 29% of diploid males sired daughters, showing their ability to produce viable sperm that can fertilize eggs. Females mated to diploid males produced all-male offspring more frequently (71%) than females mated to haploid males (27%). Daughter-producing females that had mated to diploid males produced more male-biased sex ratios than females mated to haploid males. All daughters of diploid males were triploid and sterile. Three triploid sons were also found among the offspring of diploid males. It has been suggested that this scenario, that is, diploid males mating with females and constraining them to the production of haploid sons, has a large negative impact on population growth rate and secondary sex ratio. Selection for adaptations to reduce diploid male production in natural populations is therefore likely to be strong. We discuss different scenarios that may reduce the sex determination load in C. vestalis.     

The effects of reproduction on courtship, fertility and longevity within and between alternative male mating tactics of the horned beetle, Onthophagus binodis

Life history theory provides a powerful tool to study an organism's biology within an evolutionary framework. The notion that males face a longevity cost of competing for and displaying to females lies at the core of sexual selection theory. Likewise, recent game theory models of the evolution of ejaculation strategies assume that males face a trade-off between expenditure on the ejaculate and expenditure on gaining additional matings. Males of the dung beetle Onthophagus binodis adopt alternative reproductive tactics in which major males fight for and help provision females, and minor males sneak copulations with females that are guarded by major males. Minor males are always subject to sperm competition, and consistent with theoretical expectation, minor males have a greater expenditure on their ejaculate than major males. We used this model system to seek evidence that mating comes at a cost for future fertility and/or male expenditure on courtship and attractiveness, and to establish whether these traits vary between alternative mating tactics. We monitored the lifespan of males exposed to females and nonmating populations, and sampled males throughout their lives to assess their fertility and courtship behaviour. We found a significant longevity cost of reproduction, but no fertility cost. On average, males from mating populations had a lower courtship rate than those from nonmating populations. This small effect, although statistically nonsignificant, was associated with significant increases in the time males required to achieve mating. Minor males had lower courtship rates than major males, and took longer to achieve mating. Although we did not measure ejaculate expenditure in this study, the correlation between lower courtship rate and longer mating speed of minor males documented here with their greater expenditure on the ejaculate found in previous studies, is consistent with game theory models of ejaculate expenditure which assume that males trade expenditure on gaining matings for expenditure on gaining fertilizations.     

The production of female sex pheromone in Bactrocera oleae (Rossi) young males does not influence their mating chances

In Bactrocera oleae females attract males, which is in contrast to the majority of Tephritidae. However, the major component of the secretion of the female rectal ampulla glands, 1,7‐dioxaspiro‐[5,5]‐undecane (DSU), was also isolated from the glands of young males. The DSU produced by females and young males attracts males, but not females. In this study, we investigated the role of the production of DSU in young males. The mating performances of young and old males were evaluated, as well as the male‐male courtships by old males oriented at young and old males. Young males were found not to have a mating advantage. Young males were courted more by other males. Frame‐by‐frame analysis of male wing vibrations showed that this behavior did not differ when oriented at females and young males, highlighting that young males are perceived as females by the courting males. Overall, the production of DSU in young B. oleae males did not seem to be a case of female chemical mimicry. The hypothesis that young olive fruit fly males could benefit indirectly from the DSU production, simply distracting mature males away from females, is discussed.     

Alternative male mating tactics of the substrate brooding cichlid Telmatochromis temporalis in Lake Tanganyika

Telmatochromis temporalis is a bi-parental substrate brooding cichlid endemic to Lake Tanganyika. Paired males were always larger than their mates and had territories around nests against conspecific males. However, males smaller than the paired females were found in 18% of the nests. Here we report a reproductive tactic of these small males. The small males had as heavy gonads as paired males, and the gonad somatic index (GSI) of the small males was much higher than that of the latter. The examinations of the paternity and maternity using microsatellite-DNA as a genetic marker revealed that the small males were not genetically related to the pair members, and sired some young in 3 of 5 nests. These small males did not guard the broods, suggesting that they are likely to perform reproductive parasitism as sneakers. Paired males could not enter their spawning nests due to their large size, which made it difficult to chase out sneakers once they entered the nest. Some males as small as the sneakers were found outside the territories of paired males, and their gonads were quite small. Circumstantial evidence suggests that small males have two alternative investment patterns: investing in gonad to be sneakers, and investing in growth to probably be territorial males.     

Eavesdropping in crabs: an agency for lady detection

Although conspicuous courtship displays are an effective way of attracting the attention of receptive females, they could provide valuable information to rival males on the location of these females. In fiddler crabs, males that see a receptive female wave their single, greatly enlarged claw in a highly conspicuous courtship display. We test whether other males use this courtship display to alert them to the presence of receptive females that they cannot directly see. We show that male fiddler crabs (Uca mjoebergi) eavesdrop on the courtship displays of nearby males to detect mate-searching females. This allows males to begin waving before a female becomes visible. Furthermore, males appear to adjust their waving according to the information available: eavesdropping males wave 12 times faster than non-courting males but only 1.7 times slower than males in full visual contact with the female.     

Social costs and development of nuptial coloration in male Psammodromus algirus lizards: an experiment

In the lizard Psammodromus algirus, larger and older males show orangenuptial coloration on most of the head and are dominant oversmaller and younger, albeit sexually mature, males which donot show such extensive nuptial coloration. This raises thequestion of why young, small males delay the development ofnuptial coloration until a later breeding season. We tested thehypothesis of social costs by manipulating the color of thehead of small males. The results of agonistic interactions suggestedthat small males may pay a cost in terms of being punished bylarge males. Small males with heads painted orange were stillrecognized as small by other small males, suggesting that theywould not gain in social status relative to normal, dull, small males.We also manipulated the coloration of large males. Small malesshowed a similar response toward all large males, independentof coloration. This suggests that in short-distance communication,males used other cues, such as body size and behavior, whenjudging fighting ability. In staged experiments without malecompetition, female acceptance of matings was influenced bymale body size but not by coloration because large males weremore successful in obtaining matings than were small males,and within each age/size category there was no difference inmating success between experimental and control males.     

Delayed courtship in the fiddler crab Uca musica terpsichores

Courting male fiddler crabs of the species Uca musica terpsichores congregate in the upper central portion of the colony, while receptive females leave their burrows located at the colony's periphery and wander among the communally displaying males prior to choosing a mate. I observed that courting males in a newly-established population were significantly smaller than courting males in large high-density colonies. This observation led to a series of translocation experiments designed to ascertain whether high population density influences the size (=age) at which males begin to court. Smaller courting males from a low-density population failed to court after being placed among larger courting males in a high-density population. The reciprocal translocation revealed that smaller noncourting males from the high-density population would start courting shortly after being placed in a low-density population. Smaller males placed in the high-density population were subsequently observed significantly further away from where they were initially placed than were larger males similarly translocated. The results suggest that smaller males delay courtship activities once they are forced, via encounters with larger males, to the periphery of the colony. I believe that both intrasexual selection (competition from larger males) and intersexual selection (female choice of large males) are responsible for the delay in male courtship activities.     

Female swamp sparrows do not show evidence of discriminating between the songs of peak‐aged and senescent males

Sexual selection theory predicts that females face contrasting selection pressures when choosing the age of their mate. On the one hand, older males have demonstrated their ability to survive and they may be more experienced than younger males. At the same time, however, younger males are expected to have accumulated fewer deleterious mutations in their germline as compared to older males. These contrasting pressures on female preference may result in a preference for intermediate‐aged males. A preference for males of a particular age can only be expressed, however, if females are able to identify males of different ages. We have previously shown that male swamp sparrows display age‐related changes in vocal quality, such that males display sharp increases in vocal quality in early adulthood, followed by gradual senescent declines thereafter. We have also shown that territorial males discriminate these within‐individual differences, giving stronger aggressive responses to songs of peak‐aged males than to those of senescent males. Here, we use a copulation solicitation assay to test whether females also discriminate these within‐signaler markers of senescence in song. Contrary to our prediction, females did not show any evidence of discriminating between songs recorded from peak‐aged males as compared to songs from the same males following song senescence. We suggest that this difference in demonstrated discrimination between males and females may be the result of the two sexes attending to different song characteristics.     

Male age and its association with reproductive traits in captive and wild house sparrows

Evolutionary theory predicts that females seek extra‐pair fertilizations from high‐quality males. In socially monogamous bird species, it is often old males that are most successful in extra‐pair fertilizations. Adaptive models of female extra‐pair mate choice suggest that old males may produce offspring of higher genetic quality than young males because they have proven their survivability. However, old males are also more likely to show signs of reproductive senescence, such as reduced sperm quality. To better understand why old males account for a disproportionally large number of extra‐pair offspring and what the consequences of mating with old males are, we compared several sperm traits of both captive and wild house sparrows, Passer domesticus. Sperm morphological traits and cloacal protuberance volume (a proxy for sperm load) of old and young males did not differ substantially. However, old males delivered almost three times more sperm to the female's egg than young males. We discuss the possibility of a post‐copulatory advantage for old over young males and the consequences for females mated with old males.     

The Behavioral Significance of Male Body Size in the Tarantula Hawk Wasp Hemipepsis ustulata (Hymenoptera: Pompilidae)

Large males of the tarantula hawk wasp Hemipepsis ustulata appear to have an advantage in the competition for mates. Large males are more likely to acquire perch territories used to scan for incoming receptive females and territorial males appear more likely to mate than non‐territorial males. In addition, among the males that do secure a mate, those that intercept a female on a territory are larger than those that do so elsewhere. Despite the mating advantages apparently enjoyed by larger males of this species, average male size has remained essentially constant over the last 25 yr. Moreover, larger males are not seen to employ certain competitive tactics that might otherwise enhance their reproductive success. Thus, larger males did not preferentially visit the most popular landmark territory compared to a site that attracted fewer visitors overall. Nor were larger males more likely to return to potential territories after marking, capture, and release, either immediately or on a subsequent day. Finally, although large males made up a significantly greater proportion of the males captured at two territories as the 2005 flight season progressed, over all the years of the study, receptive females have not been concentrated in the latter part of the flight seasons.     

EVOLUTION OF PLUMAGE COLOR IN MALE PIED FLYCATCHERS (FICEDULA HYPOLEUCA): EVIDENCE FOR FEMALE MIMICRY

We present the first evidence for sexual deception by female mimicry in birds. Using live, caged birds we show that territorial male pied flycatchers behave aggressively toward bright-colored males but display sexually toward female-like male intruders. We also show that the males that are fooled are those that lack recent sexual experience. All male pied flycatchers are dull-colored in winter. It is possible that young males are more constrained during the spring molt than older males since the former are more dull-colored in spring. According to the molt-constraints hypothesis a subadult plumage would be maladaptive in the breeding season. Analysis of male settling pattern at breeding sites in spring suggests that brownish males are allowed to settle closer to already-established males than dark-colored males. This result suggests an adaptive value of having a subadult plumage color, in particular for young males arriving late from spring migration. However, we also show that mimicry incurs a cost, that of increased aggression from females, which may explain why female-like males have reduced mating success.