Effects of extreme variation in female morph frequencies on the mating behaviour of male damselflies

Female-limited polymorphism is often attributed to selection to avoid excessive male mating attempts. It is encountered in various taxonomic groups, but is particularly common in damselflies, where one female morph (andromorph) typically resembles the conspecific male in colour pattern, while the other(s) (gynomorph(s)) do not. Two sets of theories have been proposed to explain the phenomenon in damselflies, which can be classified as the learned mate recognition (LMR) and male mimicry (MM) hypotheses. To test predictions of these hypotheses, we evaluated the rate of male sexual response towards female morphs and conspecific males in the damselfly Nehalennia irene. The LMR hypothesis predicts that males should respond sexually to andromorphs at greater rates in populations containing a higher relative frequency of andromorphs. The MM hypothesis predicts that males respond more often sexually to both andromorphs and males as the ratio of andromorphs to males increases. While LMR predicts that the rate of mating attempts towards gynomorphs should vary, the MM predicts that it should be relatively fixed. On experimentally presenting live specimens to focal males in five different populations with extreme variation in female morph frequencies, we observed that as the andromorph frequency and ratio of andromorphs to males increased, the proportion of male mating attempts increased on both andromorphs and males, whereas it decreased on gynomorphs. While the simplest form of the MM hypothesis is rejected, the results support specific predictions of both hypotheses and suggest that future studies should not treat these hypotheses as mutually exclusive.     

Identification of the putative aggregation pheromone components emitted by the European earwig, <Emphasis Type="Italic">Forficula auricularia</Emphasis>

The European earwig, Forficula auricularia is an invasive insect found in many temperate regions of the world and is regarded as an urban and agricultural pest of numerous crops. Several studies have shown that F. auricularia aggregate in large numbers with the use of an aggregation pheromone. However, the identity of compounds which constitute the pheromone remains elusive. Our aim was to isolate and identify the aggregation pheromone used by F. auricularia using both solvent washes of individuals and thermal desorption of substrates exposed to earwigs. Solvent washes of male, female and juvenile earwigs isolated 51 different branched and unbranched alkanes, alkenes and alkadienes. Substrates exposed to aggregating field populations in situ were demonstrated to be attractive to earwigs after less than 24 h of exposure. Analysis of these substrates using thermal desorption and solvent washes showed that hydrocarbons were the only detectable compounds laid down by earwigs on these surfaces. Significant behavioural responses were observed to synthetic blends of the unsaturated hydrocarbons containing (Z)-7-tricosene, (Z)-9-tricosene, (Z)-7-pentacosene and (Z)-9-pentacosene at ≥25 insect equivalents in field-based bioassays. However, behavioural responses to these blends proved inconsistent particularly later in the field season, possibly due to a missing component within the pheromone blend or plasticity in the pheromones production and response.     

Paternal care in the European starling,Sturnus vulgaris: nestling provisioning

The extent to which male birds in polygynous species with biparental care assist in nestling feeding often varies considerably between nests of different mating status. Both how much polygynous males assist and how they divide their effort between nests may have a profound effect on the evolution of mating systems. In this study we investigated how males in the facultatively polygynous European starling Sturnus vulgaris invested in their different nests. The amount of male assistance affected the quality of the offspring. Polygynous males invested as much as monogamous males, but divided their effort asymmetrically between nests, predominantly feeding nestlings of first-mated (primary) females. Although females partly compensated for loss of male assistance, total feeding frequency was lower at primary females’ nests than at monogamous females nests. Secondary females received even less assistance with nestling rearing, and the extent to which males assisted decreased with the length of the interval between the hatching of the primary and secondary clutches. These results are contrasted with those from a Belgian populations of starlings with a much more protracted breeding season and thus greater opportunities for males to attract additional mates during the nestling rearing period. The results show that both the “defence of male parental investment model” and the “asynchronous settlement model” have explanatory power, but that their validity depends on the potential length of the breeding season. Received: 21 July 1995/Accepted after revision: 13 July 1996     

Sex allocation in a monomorphic seabird with a single-egg clutch: test of the environment, mate quality, and female condition hypotheses

Sex allocation theory posits that mothers should preferentially invest in sons when environmental conditions are favorable for breeding, their mates are of high quality, or they are in good body condition. We tested these three hypotheses in rhinoceros auklets (Cerorhinca monocerata), monomorphic seabirds that lay a single-egg clutch, in 2 years that differed in environmental conditions for breeding. Results supported the environment and mate quality hypotheses, but these effects were interactive: offspring sex was independent of paternal traits in the poor year for breeding, while females mated to larger and more ornamented males reared more sons in the better year. Conversely, offspring sex was unrelated to female condition, as indexed by hatching date. We propose that good rearing conditions enable females to rear sons possessing the desirable phenotypic attributes of their mates. Results also supported two critical assumptions of sex allocation theory: (1) dimorphism in offspring condition at independence: daughters fledged with higher baseline levels of corticosterone than sons and (2) differential costs of rearing sons versus daughters: mothers rearing sons when environmental conditions were poor completed parental care in poorer condition than mothers rearing daughters in the same year and mothers rearing either sex when conditions were better. These novel results may help to explain the disparate results of previous studies of avian sex allocation.     

The morphology and behavior of dimorphic males in Perdita portalis (Hymenoptera : Andrenidae)

Summary In Perdita portalis, a ground nesting, communal bee, males are clearly dimorphic. The two male morphs are easily distinguished based on head size and shape into (1) a flight-capable, small-headed (SH) morph that resembles the males of other closely related species and (2) a flightless, large-headed (LH) morph that possesses numerous derived traits, such as reduced compound eyes, enlarged facial foveae and fully atrophied indirect flight muscles. The SH morph occurs exclusively on flowers while the LH morph is found only in nests with females. While on flowers, SH males are aggressive, fighting with conspecific males and heterospecific male and female bees, and they mate frequently with foraging females. Using artificial observation nests placed in the field, I observed the behavior of females and LH males within their subterranean nests. LH males are aggressive fighters; males attacked each other with mandibles agape, and male-male fights always ended in the death of one male. LH males are highly attentive to the reproductive behavior of females; they spend increasing amounts of time near open cells during cell provisioning, and mating only takes place immediately prior to oviposition when females are forming the accumulated pollen and nectar into a ball. Based on larvae reared to adulthood in the laboratory, the two male morphs occur in equal proportions. The behavior of males in closely related species, especially P. texana, and the origin and maintenance of male dimorphism are discussed.     

Evolution of male mating behavior: male spadefoot toads preferentially associate with conspecific males

The evolution of male breeding aggregations is difficult to explain because males may reduce their reproductive success by associating with their closest competitors. We examined aggregative behavior by male New Mexico spadefoot toads, Spea multiplicata, which form breeding choruses in rain-filled pools. We specifically asked whether males are attracted to conspecific calls and, if so, whether they preferentially associate with those male calls that are also attractive to females. Field observations revealed that males showed significant clustering with conspecifics within breeding ponds, whereas laboratory phonotaxis experiments revealed that males preferentially associated with conspecific male calls. Moreover, when males were presented with conspecific calls that differed in call rate, smaller males associated with the stimulus preferred by females (average call rate). Thus, males appear to evaluate the attractiveness of competitors using the same trait employed by females to assess potential mates, and males adjust their positions relative to competitors depending on their size. We discuss these results in the light of several current hypotheses on the adaptive significance of male breeding aggregations. Received: 20 December 1999 / Accepted: 18 March 2000     

Parental investment, adult sex ratios, and sexual selection in a socially monogamous seabird

Although most birds are monogamous, theory predicts that greater female parental investment and female-biased adult sex ratios will lower the polygyny threshold. This should result in polygynous mating, unless obligate biparental care or the spatial and temporal distribution of fertilizable females constrains a male’s ability to take advantage of a lowered polygyny threshold. Here we present data on the extent of male sexually dimorphic plumage, adult sex ratios and breeding season synchrony in three populations of a socially monogamous seabird, the brown booby Sula leucogaster. For one of these populations, San Pedro Mártir Island, we also present data on differences in male and female parental investment, mortality and probability of pairing. The extent of plumage dimorphism varied among populations. Sex ratios were female biased in all populations. On San Pedro Mártir Island, parental investment was female biased, females failed more often than males to find a mate, but there was no polygyny. We suggest that on San Pedro Mártir: (1) a period of obligate biparental care coupled with a relatively synchronous breeding season constrained the ability of males to take advantage of a high environmental polygamy potential and (2) the resulting socially monogamous mating system, in combination with the female-biased adult sex ratio, caused females to be limited by the availability of males despite their greater parental investment. Received: 18 November 1999 / Accepted: 24 January 2000     

Polyandrous mating in treetops: how male competition and female choice interact to determine an unusual carnivore mating system

The diversity of mammalian mating systems is primarily shaped by sex-specific reproductive strategies. In the present study, we explored determinants and consequences of a unique mating system exhibited by fossas (Cryptoprocta ferox), the largest Malagasy carnivore, where females mate polyandrously on traditional mating trees, and males exhibit intrasexual size dimorphism. Males face both contest and scramble competition, and inter-sexual size dimorphism can be pronounced, but its magnitude depends on the male morph. Using a continuous behavioral observation of six estrous females over 4 years, we investigated correlates of male contest competition and female choice based on 316 copulations. Furthermore, we assessed correlates of male scramble competition based on testes size and movement data obtained from GPS tracking. We found that females dominated males regardless of their smaller size and that females actively solicited copulations. Heavy males had highest mating success during the female’s peak mating activity, but were discriminated against afterwards. Female choice and male–male competition thus converged to generate a mating advantage for heavier males. Our results suggest that females actively seek polyandrous matings, presumably for indirect genetic benefits. Since body mass is the major determinant of male mating success and is at the same time dependent on the degree of sociality and associated hunting mode of the respective male morph, a male’s feeding ecology is likely to influence its reproductive tactic. A combination of benefits from female polyandry and the consequences of different subsistence strategies may thus ultimately explain this unusual mating system.     

Tests of the harassment-reduction function and frequency-dependent maintenance of a female-specific color polymorphism in a damselfly

Color polymorphisms have provided classical examples of how frequency-dependent selection maintains genetic variation in natural populations. Here we tested for the first time, the hypothesized adaptive function of a female-specific color polymorphism in odonates to lower male harassment towards females generally. Under conditions controlling for sex ratio, population density and morph frequency, we also tested two major frequency-dependent selection hypotheses for the maintenance of the polymorphism. Using groups of captive Enallagma hageni, whose females are either green or a male-like blue, we varied morph frequency at two sex ratios. We quantified sexual harassment towards females by visual observations, and by the presence of dust on females that was transferred from dusted males. Per capita harassment rate for the female-monomorphic treatments did not differ from that of the female-polymorphic treatments. At a male-biased sex ratio, per capita harassment rate towards blue, but not green females increased with morph frequency, providing partial support for frequency-dependent selection resulting from male learning of female morphs. Even at high frequency, green females were not harassed more than blue, contrary to the prediction that males should always recognize green females as mates. Moreover, frequency-dependent harassment towards blue females was not detectable using harassment measured with dust evidence, which greatly underestimated the incidence of sexual harassment. Our findings identified problems with the use of insectaries and the dusting technique to quantify male sexual harassment towards females, as well as with a past insectary experiment on Ischnura elegans that failed to demonstrate frequency-dependent harassment.     

Scramble competition selects for greater tailfin size in male red-spotted newts (Amphibia: Salamandridae)

Darwin predicted that scramble competition for access to reproductive females would result in sexual dimorphism of locomotory structures, but direct evidence for this is extremely rare. I examined the relationship between variation in tailfin size and mating success in a field and laboratory study of red-spotted newts, Notophthalmus viridescens. Over three breeding seasons, male tailfin size was positively correlated with variation in male amplexus frequency, and indirectly correlated with male insemination frequency. In a laboratory study, I confirmed that males' ability to capture females is affected by variation in tailfin size. This is the first study to show that naturally occurring variation in male locomotory structures affects male mating success. It corroborates the prediction that scramble competition leads to sexual selection on locomotory structures and, potentially, to dimorphism in these structures. Received: 16 April 1999 / Received in revised form: 16 May 1999 / Accepted: 12 June 1999     

Maternal investment in rhesus macaques (Macaca mulatta): reproductive costs and consequences of raising sons

Maternal investment in offspring is expected to vary according to offspring sex when the reproductive success of the progeny is a function of differential levels of parental expenditure. We conducted a longitudinal investigation of rhesus macaques to determine whether variation in male progeny production, measured with both DNA fingerprinting and short tandem repeat marker typing, could be traced back to patterns of maternal investment. Males weigh significantly more than females at birth, despite an absence of sex differences in gestation length. Size dimorphism increases during infancy, with maternal rank associated with son’s, but not daughter’s, weight at the end of the period of maternal investment. Son’s, but not daughter’s, weight at 1 year of age is significantly correlated with adult weight, and male, but not female, weight accounts for a portion of the variance in reproductive success. Variance in annual offspring output was three- to fourfold higher in males than in females. We suggest that energetic costs of rearing sons could be buffered by fetal delivery of testosterone to the mother, which is aromatized to estrogen and fosters fat accumulation during gestation. We conclude that maternal investment is only slightly greater in sons than in daughters, with mothers endowing sons with extra resources because son, but not daughter, mass has ramifications for offspring sirehood. However, male reproductive tactics supersede maternal investment patterns as fundamental regulators of male fitness. Received: 23 July 1999 / Received in revised form: 23 February 2000 / Accepted: 13 March 2000     

Provisional rejection of three alternative hypotheses on the maintenance of a size dichotomy in males of Dawson’s burrowing bee,Amegilla dawsoni (Apidae,Apinae, Anthophorini)

I examine three alternative hypotheses on the male size dimorphism of Dawson’s burrowing bees (Amegilla dawsoni) in which there are large (major) and small (minor) males. One possibility is that minor males are simply the incidental byproduct of environmental conditions that prevent females from provisioning brood cells optimally. This hypothesis is not supported by the finding that males of intermediate size are consistently rare in populations sampled across years and in different regions, nor can it easily account for the absence of a size dichotomy in females. A second possibility is that minors represent a “best of a bad job” response of those females that are small or otherwise disadvantaged. However, presumptive male siblings sometimes include both majors and minors, a result not predicted from this hypothesis. A third explanation is that female brood provisioning strategy results in the production of minors and majors with equal fitness benefit to fitness cost ratios. However, although it is true that minor males weigh on average about half what a major weighs, and so represent approximately half the provisioning expense of a major, minor males on average appear to secure far fewer than half the number of matings of majors. If the estimate of mating success of minors is accurate, the net gain to females from producing a minor son is unlikely to equal that derived from a major son. Therefore the third hypothesis must also be tentatively rejected, although with caution given the uncertainties in estimating the relative costs and benefits of producing major and minor sons. Received: 12 January 1996/Accepted after revision: 27 April 1996     

Female resistance and male preference in a stream-dwelling isopod: effects of female molt characteristics

In the stream-dwelling isopod, Lirceus fontinalis, mating contests between males and females occur prior to pair formation. We examined the relative contribution of male preference and female resistance to contest outcomes. We first quantified male and female behavior during typical mating interactions and examined the relationship between time until molt (TTM) and mating outcomes. We then examined the role of male preference and female resistance in determining mating outcomes when females differed in molt type (growth, egg deposition) and appeared to differ in TTM (due to hormone applications). Both male preference and female resistance contributed to different components of the mating sequence but female resistance ultimately determined whether or not pair formation occurred. Males expressed a preference for females that appeared to be close to molt, using variation in levels of molt hormone as a cue. However, males did not discriminate between females based on molt type. Received: 5 March 1999 / Received in revised form: 10 August 1999 / Accepted: 16 October 1999     

Population frequencies of alternative male phenotypes in tree lizards: geographic variation and common-garden rearing studies

Tree lizards (Urosaurus ornatus) vary in throat fan (dewlap) color. Earlier, we described five dewlap types (Orange, Orange-Blue, Yellow, Yellow-Blue, and Blue), and reported that only males had blue in the dewlap and that presence or absence of a discrete blue patch was correlated with male alternative reproductive phenotypes in a central Arizona population. Here, with a modified scheme characterizing two dewlap elements, background color (orange, yellow, blue) and blue patch occurrence, we assessed: (1) sexual, annual, and geographic variation in the frequencies of dewlap elements; (2) simple habitat correlates; and (3) the effects of laboratory rearing regime on dewlap type. Within a population, frequencies of males and females expressing orange or yellow backgrounds did not differ, suggesting that control of background is similar in the sexes. Within several populations, frequencies of the dewlap elements did not differ across years (and probably generations), indicating that phenotype frequencies are relatively stable. Among five populations frequencies of background colors varied, as did frequencies of male types (blue patch present or absent). Dewlap frequencies did not correlate with habitat (boulders or mesquite trees), although few populations were sampled. In male and female offspring reared from eggs to sexual maturity in a common-garden laboratory study, background color frequencies in both sexes and blue patch frequencies in males differed among offspring from different populations. Offspring frequencies matched respective parental population frequencies. Results suggest that among-population variation in frequencies of the two dewlap elements are mediated by differences in genetics, in maternal effects, or both. Thus, differences in male behavior functionally linked to the blue patch also may be controlled by genetic or maternal effects. Received: 17 January 1997 / Accepted after revision: 30 August 1997     

Exaggerated male eye span influences contest outcome in stalk-eyed flies (Diopsidae)

Evolution of male weapons or status signals has been hypothesized to precede evolution of female mating preferences for those traits. We used staged male fights among three species of Malaysian stalk-eyed flies (Diptera: Diopsidae) to determine if elongated eye span, which is preferred by females in two sexually dimorphic species, influences contest outcome. Extreme sexual dimorphism, with large males possessing longer eye span than females, is shared by Cyrtodiopsis whitei and C. dalmanni. In contrast, C. quinqueguttata exhibits a more ancestral condition – short, sexually monomorphic eye stalks. Videotape analysis of 20-min paired contests revealed that males with larger eye span and body size won more fights in the dimorphic, but not monomorphic, species. To determine if males from the dimorphic species use eye span directly to resolve contests, we competed male C. dalmanni from lines that had undergone artificial selection for 30 generations to increase or decrease eye span. We found that eye span, independently of body size, determines contest outcome in selected-line males. Furthermore, in both dimorphic species, the average encounter duration declined as the eye span difference between contestants increased, as expected if males use eye span to assess opponent size. The number of encounters also increased with age in dimorphic, but not monomorphic, species. Selected-line males did not differ from outbred males in either fight duration or number of encounters. We conclude that exaggerated male eye stalks evolved to influence both competitive interactions and female mating preferences in these spectacular flies. Received: 20 July 1998 / Received in revised form: 2 February 1999 / Accepted: 12 March 1999     

A test of male mating and hunting success in the kestrel: the advantages of smallness?

We tested female choice for male wing and tarsus length and body mass in the kestrel (Falco tinnunculus), a species in which males average about 10% smaller than females. We also studied how male characters are related to their hunting success. In the laboratory, females preferred lighter males with shorter tarsi as mates, if the difference in those characters between competing males was larger than average. Lighter and shorter-winged males seemed to be better hunters than heavier and longer-winged males. Field observations in a year in which voles were scarce suggested that shorter-winged males were also better food providers in courtship feeding than longer-winged males,although in good vole years such a relationship was not found. We argue that females may prefer to pair with smaller males, because they have higher flight performance and better hunting success than heavier males. By doing so, females may gain direct breeding advantages. We conclude that both female choosiness and the hunting efficiency of males well contribute to reversed sexual size dimorphism (RSD, females larger than males) in the kestrel. Received: 18 July 1995/Accepted after revision: 17 August 1996     

Frequency-dependent male mate harassment and intra-specific variation in its avoidance by females of the damselfly Ischnura elegans

We focused on male harassment on different female color morphs of the damselfly Ischnura elegans and on variation in morph-specific mating avoidance tactics by females. In I. elegans, one of the female morphs is colored like the conspecific male (andromorphs) while the other morphs are not (gynomorphs). Our first goal was to quantify morph-specific male mating attempts, hence male harassment, in populations with manipulated population parameters (densities, sex ratios, and proportion of andromorphs). Second, we examined the female's perspective by looking for potential differences in morph-specific mating avoidance tactics and success of those tactics in a natural population. Differences in population conditions did influence the number of male mating attempts per morph. The less frequent female morph was always subject to fewer mating attempts, which contradicts earlier hypotheses on mimicry, but supports those that assume that males learn to recognize female morphs. Gynomorphs occupy less open habitat and often fly away when a male approaches, while andromorphs use more open habitat, do not fly large distances and directly face approaching males. Female morphs did not differ in the proportion of successful mating-avoidance attempts. Our results suggest that the maintenance of the color polymorphism is most probably the result of interactive selective forces depending on variation in all population conditions, instead of solely density- or frequency-dependent selection within populations.     

Quantitative variation in ecological and hormonal variables correlates with spatial organization of pronghorn (Antilocapra americana) males

Whereas variation in pronghorn (Antilocapra americana) spatial organization is well documented, underlying ecological or physiological explanations are not well understood. This study quantitatively describes spacing systems of pronghorn males and correlates of their spatial organization. I collected behavioral data from two populations in South Dakota (Wind Cave) and Montana (Bar Diamond) to determine if males differed in space use, response to intruders, and behavior patterns indicative of area defense. I measured sex ratio and population density, and I examined characteristics of food resources, including forb species diversity, richness, coverage, biomass, and nitrogen content, and how they changed during the growing season. I also collected and analyzed fecal samples to determine if males differed in testosterone concentrations. Pronghorn males at Wind Cave were more territorial than males at Bar Diamond, although males at Bar Diamond became more territorial during the second year. The forb community at Wind Cave was more diverse, contained greater amounts of forbs later in summer, and had a higher nitrogen content later in summer. Population density was lower at Wind Cave, although density dropped at Bar Diamond during the second year, and sex ratios were skewed toward males at Bar Diamond. Finally, males at Wind Cave had higher testosterone concentrations than did Bar Diamond males, although differences were not statistically significant. With lower population density and higher forb abundance and quality, food resources were more economically defensible at Wind Cave, and males were more territorial there. Analyses using these and other pronghorn populations revealed that population density and sex ratio correlated weakly with spatial organization, whereas precipitation correlated most strongly, which suggests plant productivity has a powerful role in determining pronghorn territoriality. Received: 16 June 1999 / Received in revised form: 21 September 1999 / Accepted: 31 December 1999     

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.     

Alternative mating tactics in dimorphic males of the harvestman <Emphasis Type="Italic">Longiperna concolor</Emphasis> (Arachnida: Opiliones)

Intense male–male competition for females may drive the evolution of male morphological dimorphism, which is frequently associated with alternative mating tactics. Using modern techniques for the detection of discontinuous allometries, we describe male dimorphism in the Neotropical harvestman Longiperna concolor, the males of which use their elongated, sexually dimorphic legs IV in fights for the possession of territories where females lay eggs. We also tested three predictions related to the existence of alternative mating tactics: (1) if individuals with relatively longer legs IV (majors) are more likely to monopolize access to reproductive resources, they are expected to remain close to stable groups of females more than individuals with relatively shorter legs IV (minors) do; (2) if minors achieve fertilization by moving between territories, they are expected to be less faithful to specific sites; and (3) majors should be observed in aggressive interactions more often. We individually marked all the individuals from a population of Longiperna during the reproductive season and recorded the location of each sighting for males and females as well as the identity of males involved in fights. Majors were more likely to have harems, and large majors were even more likely to do so. Majors were more philopatric and all males involved in fights belonged to this morph. These results strongly suggest that the mating tactic of the majors is based on resource defense whereas that of the minors probably relies on sneaking into the territories of the majors and furtively copulating with females.