The courtship behavior of the cabbage moth,Mamestra brassicae (Lepidoptera: Noctuidae), and the role of male hair-pencils

The courtship behavior of the cabbage moth, Mamestra brassicae(L.), was studied in moving air conditions in a wind tunnel, using video techniques. Quantitative analyses were undertaken to determine the behavioral sequence occurring in the courtship. Comparison of successful and unsuccessful courtship suggested that courtship success was more dependent on the behavior of the female than that of the male. In an attempt to elucidate the function of the male hair-pencils (HPs), courtships involving males without HPs were also studied. HP removal did not affect the overall courtship success rate of males, but detailed analysis showed significant changes infernale behavior during such courtships. HP removal also affected female behavior following pair formation, with females struggling more when paired with males without HPs. Consequently, it is proposed that the HP volatiles act as an arrestant for the female, both during courtship and after pair formation, to increase female acceptance and to prevent premature termination of copulation. Experiments were also conducted to test previous hypotheses for HP function. However, no evidence was found to suggest that the HP volatiles in M. brassicaeact to attract females, affect female calling behavior, or affect the behavior of other males. A further possible function of HPs in defense is discussed.     

Do Male Veiled Chameleons,Chamaeleo calyptratus,Adjust their Courtship Displays in Response to Female Reproductive Status?

Variation in male courtship behavior may be due to inherent differences among males or may arise from males adjusting their courtship displays according to female responsiveness. Female veiled chameleons, Chamaeleo calyptratus , exhibit two distinctive suites of body coloration and behavior patterns that vary according to receptive and non-receptive stages of their reproductive cycle. We presented male chameleons with both receptive and non-receptive females, and recorded differences in their mating frequency, courtship intensity and courtship behavior patterns. As expected, males were more likely to court and attempt mating with receptive females. Although fewer males courted non-receptive females, their courtship displays were significantly longer than those directed towards receptive females. Males also adjusted the contents of their displays according to female reproductive condition. Certain behavior patterns were unique to courtship displays directed towards each class of females. Males exhibited the behavior pattern `head roll' only when paired with receptive females, and `chin rub' was displayed only during courtship of non-receptive females. We hypothesize that these differences in male courtship frequency, intensity and content reflect differences in female reproductive value. Although males may benefit from mating with both receptive and non-receptive females, the costs associated with courtship may depend on female responsiveness. Thus, males adjust their courtship tactics accordingly.     

The hormonal response of female European Stonechats to a territorial intrusion: the role of the male partner

In many bird species, the female participates in defending a pair's breeding territory, however, the endocrine control mechanism of female aggressive behavior is largely unknown. The general statement that androgens are involved in the regulation of aggressive behavior is based on studies conducted only in males. Here, we tested whether paired female stonechats show a hormonal response to a simulated male territorial intruder. Since in males of territorial bird species androgen levels usually increase following a male-male encounter, we measured androgen-levels before and after a simulated male intrusion. In addition, we measured estradiol, the main gonadal hormone in females, and corticosterone, a stress hormone. The results show that a male intruder does not affect any of the measured hormones in females. In a second experiment, we also tested whether the endocrine state of the male partner affects the hormonal response of females to a male intruder by comparing the hormonal response of females paired with pharmacologically castrated males and females paired with control males. Females paired with pharmacologically castrated males had lower corticosterone levels both before and after the intrusion than females paired with control males. Additionally, in both groups, female corticosterone levels were increased following a male intrusion. We suggest that the differences found between females paired with pharmacologically castrated males and females paired with control males are due to differences in intra-pair interactions.     

Courtship Solicitation by Females of the Barred Sulphur Butterfly (<Emphasis Type="Italic">Eurema daira</Emphasis>) (Lepidoptera: Pieridae)

Virgin females of the subtropical pierid butterfly Eurema daira were observed to actively solicit male courtship. The resulting interactions involved both aggressive contact with male individuals and elaborate female posturing. Cage-based trials showed that there was a direct relationship between the frequency of courtship solicitation attempts and female age. Virgin females under 3 days old showed little or no interest in initiating courtship. By contrast, 23.2 percent of the virgin females over three days old actively solicited available males with peak solicitation behavior exhibited from five day old individuals.     

Behavioral, hormonal, and morphological responses of free-living male pied flycatchers to estradiol treatment of their mates

A field experiment was performed implanting female pied flycatchers (Ficedula hypoleuca) during the nest-building period with silastic tubes containing 17 beta-estradiol. Control females were given empty silastic tubes. The pied flycatcher is a polygamous and polyterritorial bird species. During two successive breeding seasons effects on reproductive behavior and the reproductive systems of males were studied. Reproductive success was not affected by the treatment. Estradiol treatment of females caused marked changes in the behavior of males, increasing aggressive and mate-guarding behavior. The results of the present study also support the idea that cuckoldry is a problem for the territory holder. Fewer males paired with estradiol-treated females established secondary territories, and significantly more of the polyterritorial males from the experimental population showed up in the home-territory when a simulated territorial intrusion was performed there. Control males were much more successful in getting a second female to breed. Spermatogenesis and hormonal cycles (DHT, LH, and testosterone) in males were not prolonged as a result of estradiol treatment of the females.     

Previous Motor Experience Enhances Courtship Behavior in Male Cricket <Emphasis Type="Italic">Gryllus bimaculatus</Emphasis>

In crickets Gryllus bimaculatus, flight has been shown to be able to promote aggressive encounters between males and to suppress escape behavior. The aim of this study was to examine the influence of flight on male behavior in male–female interactions. We found that flown males demonstrate enhanced courtship behavior. The latency of calling song was significantly shorter, while the relative total duration of singing as well as the duration of singing episodes longer in flown males than in the control. Mating rate was also significantly higher in the experimental group containing flown males. The results suggest that, in addition to previously reported effects on aggressiveness and escape, flying has a profound accelerating effect on male courtship behavior.     

雌星豹蛛性信息素的行为学证据

采用星豹蛛(Pardosa astrigera)成熟雄蛛求偶时潜伏时间、静止时间、身体震动和第一墩步足伸展次数等行为参数,利用行为学方法测定了不同性别、日龄和生殖状态的星豹蛛雌蛛释放的拖丝对雄蛛求偶行为的影响。结果表明,雄蛛第一对步足伸展和身体震动等典型求偶行为是进行星豹蛛性信息素生物测定的可靠评价指标。星豹蛛雄蛛能通过拖丝上的性信息素辨别星豹蛛的性别、日龄和生殖状态。雄蛛在成熟3周未交配雌蛛拖丝处理过滤纸上潜伏时间和静止时间都相应最短,在交配未产卵雌蛛、雌亚成蛛和成熟雄蛛拖丝上时间中等,在卵孵化雌蛛拖丝处理滤纸上潜伏时间和静止时间都相应最长。成熟3周未交配雌蛛和交配未产卵雌蛛释放的拖丝都能引起雄蛛第一对步足伸展和身体震动等典型求偶行为,雄蛛对成熟3周未交配雌蛛拖丝典型求偶行为的频率都相应高于交配未产卵雌蛛。卵孵化雌蛛释放的拖丝虽也能引起雄蛛第一对步足伸展行为,但其伸展频率显著降低;而其它拖丝都不能引起雄蛛典型求偶行为。     

同种雄性竞争对手的存在对星豹蛛雄蛛求偶和交配行为的影响

越来越多的研究发现,雄性产生精子(精液)也需付出代价。雄性除了依据配偶质量和竞争对手的竞争强度适应性调整生殖投入外,雄性在求偶和交配行为上也相应产生适应性反应,求偶和交配行为具有可塑性。目前雄性求偶和交配行为可塑性研究主要集中于雌性多次交配的类群中,在雌性单次交配的类群中研究甚少。以雌蛛一生只交配一次而雄蛛可多次交配的星豹蛛为研究对象,比较:(1)前一雄性拖丝上信息物质对后续雄蛛求偶和交配行为的影响,(2)雌雄不同性比对雄蛛求偶和交配行为的影响。研究结果表明,星豹蛛前一雄蛛拖丝上的信息物质对后续雄蛛求偶潜伏期、求偶持续时间和交配持续时间都没有显著影响,但前一雄蛛拖丝上的信息物质对后续雄蛛求偶强度有显著抑制作用。同时,性比对星豹蛛雄蛛求偶和交配行为都没有显著影响。可见,星豹蛛雄蛛对同种雄性拖丝上的化学信息可产生求偶行为的适应性调整,而对性比不产生适应性反应。     

Effects of Male Vocal Learning on Female Behavior in the Budgerigar, Melopsittacus undulatus

Parrots are unusual among birds and animals in general in the extent of their ability to learn new vocalizations throughout life and irrespective of season. The budgerigar (Melopsittacus undulatus), a small parrot that is well suited for laboratory studies, has been the subject of numerous studies investigating the neurobiology of vocal learning. To date, few studies have focused on the function of vocal imitation by parrots. Previous work from our research group has shown that vocal imitation in budgerigars is sex‐biased, as males paired with females learn vocalizations from their new mates, but not vice versa. This bias led us to hypothesize that vocal learning has a reproductive function. To test this hypothesis, we conducted two experiments. In the first experiment, we tutored males so that they could produce a call similar to one shared by a group of experimental females. The experimental females were then presented with one of the tutored males and another, equally unfamiliar, male that had not been tutored. We found that the females spent a greater proportion of time in proximity of, and made more affiliative displays toward, the tutored males. In the second experiment, seven males received small bilateral brain lesions that disrupt vocal learning. These males and an equal number of control males were then released into an aviary containing females and reproductive resources. We found that lesioned and control males were equally successful in obtaining social mates, but females mated to lesioned males were more likely to engage in extra‐pair activities. These experiments indicate that a male's ability to imitate a female's call can influence the sexual behavior of the female even though lack of imitation ability does not appear to influence social pairing. We hypothesize that mate choice in budgerigars has multiple stages. Upon meeting a strange male, a female quickly assesses its ability for social acquisition of calls by the presence or absence of a call type similar to its own in its repertoire. As courtship proceeds into pair formation, the female assesses the ability of male to learn more directly by the extent of the male's perfection of imitation.     

Low mate encounter rate increases male risk taking in a sexually cannibalistic praying mantis

Male praying mantises are forced into the ultimate trade-off of mating versus complete loss of future reproduction if they fall prey to a female. The balance of this trade-off will depend both on (1) the level of predatory risk imposed by females and (2) the frequency of mating opportunities for males. We report the results of a set of experiments that examine the effects of these two variables on male risk-taking behavior and the frequency of sexual cannibalism in the praying mantis Tenodera sinensis. We experimentally altered the rate at which males encountered females and measured male approach and courtship behavior under conditions of high and low risk of being attacked by females. We show that male risk taking depends on prior access to females. Males with restricted access to females showed greater risk-taking behavior. When males were given daily female encounters, they responded to greater female-imposed risk by slowing their rate of approach and remained a greater distance from a potential mate. In contrast, males without recent access to mates were greater risk-takers; they approached females more rapidly and to closer proximity, regardless of risk. In a second experiment, we altered male encounter rate with females and measured rates of sexual cannibalism when paired with hungry or well-fed females. Greater risk-taking behavior by males with low mate encounter rates resulted in high rates of sexual cannibalism when these males were paired with hungry females.     

Size-dependent precopulatory behavior as mate-securing tactic in the Japanese stag beetle, Prosopocoilus inclinatus (Coleoptera; Lucanidae)

Males of the Japanese stag beetle Prosopocoilus inclinatus show dimorphism in body size. Since females frequently resist male courtship behavior, males often fail to mate after encounters with females. The males of two morphs showed different precopulatory behavior. During encounters with females, small males acted more persistently against females resistance than large males by grasping the female more solidly and as a result, succeeded in copulation more frequently. This persistent precopulatory behavior could be regarded as an alternative mating tactic of small males that are inferior to large males in direct physical competition.     

Pheromonal and behavioral cues trigger male-to-female aggression in Drosophila

Appropriate displays of aggression rely on the ability to recognize potential competitors. As in most species, Drosophila males fight with other males and do not attack females. In insects, sex recognition is strongly dependent on chemosensory communication, mediated by cuticular hydrocarbons acting as pheromones. While the roles of chemical and other sensory cues in stimulating male to female courtship have been well characterized in Drosophila, the signals that elicit aggression remain unclear. Here we show that when female pheromones or behavior are masculinized, males recognize females as competitors and switch from courtship to aggression. To masculinize female pheromones, a transgene carrying dsRNA for the sex determination factor transformer (traIR) was targeted to the pheromone producing cells, the oenocytes. Shortly after copulation males attacked these females, indicating that pheromonal cues can override other sensory cues. Surprisingly, masculinization of female behavior by targeting traIR to the nervous system in an otherwise normal female also was sufficient to trigger male aggression. Simultaneous masculinization of both pheromones and behavior induced a complete switch in the normal male response to a female. Control males now fought rather than copulated with these females. In a reciprocal experiment, feminization of the oenocytes and nervous system in males by expression of transformer (traF) elicited high levels of courtship and little or no aggression from control males. Finally, when confronted with flies devoid of pheromones, control males attacked male but not female opponents, suggesting that aggression is not a default behavior in the absence of pheromonal cues. Thus, our results show that masculinization of either pheromones or behavior in females is sufficient to trigger male-to-female aggression. Moreover, by manipulating both the pheromonal profile and the fighting patterns displayed by the opponent, male behavioral responses towards males and females can be completely reversed. Therefore, both pheromonal and behavioral cues are used by Drosophila males in recognizing a conspecific as a competitor.     

Singing-Related Activity in Anterior Forebrain of Male Zebra Finches Reflects Courtship Motivation for Target Females

A critical function of singing by male songbirds is to attract a female mate. Previous studies have suggested that the anterior forebrain system is involved in this courtship behavior. Neural activity in this system, including the striatal Area X, is strikingly dependent on the function of male singing. When males sing to attract a female bird rather than while alone, less variable neural activity results in less variable song spectral features, which may be attractive to the female. These characteristics of neural activity and singing thus may reflect a male''s motivation for courtship. Here, we compared the variability of neural activity and song features between courtship singing directed to a female with whom a male had previously formed a pair-bond or to other females. Surprisingly, across all units, there was no clear tendency for a difference in variability of neural activity or song features between courtship of paired females, nonpaired females, or dummy females. However, across the population of recordings, there was a significant relationship between the relative variability of syllable frequency and neural activity: when syllable frequency was less variable to paired than nonpaired females, neural activity was also less variable (and vice-versa). These results show that the lower variability of neural activity and syllable frequency during directed singing is not a binary distinction from undirected singing, but can vary in intensity, possibly related to the relative preference of a male for his singing target.     

Discrimination of conspecific individuals via cuticular pheromones by males of the cricket Gryllus bimaculatus

Cuticular substances on the body surface of crickets serve as pheromones that elicit a variety of different behaviors in male crickets. Antennal contact between males and females resulted in courtship behavior, and that between two males resulted in aggressive displays. As a first step in elucidating how crickets recognize and discriminate individuals, behavioral responses of male individuals to cuticular substances of conspecific males or females were investigated. The behavioral responses of males to antennal or palpal stimulation with an isolated antenna from a male or a female were recorded. To both antennal and palpal stimulation with female antennae, the majority of males responded with courtship behavior; to stimulation with male antennae, males responded with aggressive displays. To gain insight into the chemical nature of the behaviorally relevant components, isolated antennae were washed in either n-hexane, acetone or ethanol before behavior assays. Washed antennae no longer elicited courtship or aggressive responses in males. Next, polypropylene fibers were smeared with substances from the body surface of females and used for antennal stimulation. This experiment showed that the quality and quantity of cuticular substances appear to be highly age-dependent. Significantly more males responded with courtship behavior to cuticular substances from younger females. Isolated males generally showed higher levels of aggression than males reared in groups. Grouped males also were more likely to display courtship behavior towards antennae from younger females, and aggressive behavior towards antennae from older females. These results suggest that male discrimination of mating partners depends on the nature of female cuticular substances.     

Call Convergence within Groups of Female Budgerigars (Melopsittacus undulatus)

The budgerigar (Melopsittacus undulatus) is a promising model species for the study of adult vocal learning. To date, several studies have confirmed the existence of vocal plasticity and, more importantly, rapid imitation of contact calls by adult male budgerigars. Vocal learning has not been investigated in female budgerigars, however. Since one likely function of the contact call is to denote group affiliation, we tested the hypothesis that female budgerigars, when placed into groups, would develop a shared contact call. We recorded the contact call repertoires of eight adult female budgerigars that were unfamiliar with one another, then placed them into two groups. Each group was deprived of visual contact with other birds. Recording sessions continued for the subsequent 8 wks, and behavioral observations were also conducted during this time. Within 4–7 wks, females in both groups converged on a common call type. This rate of convergence is slower than that observed in prior experiments limited to male birds, and much slower than vocal imitation by male budgerigars paired with females. Therefore, while our study documents vocal plasticity in adult female budgerigars, it also suggests that female budgerigars learn new vocalizations more slowly than males do.     

Temporal patterning of external stimuli and reproductive behaviour in female budgerigars

The role of stimuli from the nestbox, the male and breeding females in regulating the course of reproductive development in female budgerigars is examined. When females were paired with males but deprived of nestboxes no development of the overy, oviduct or brood patch occurred. Females visually and auditorily isolated from males entered their nestboxes, but fewer (8 per cent) laid eggs than females paired with males (75 per cent). More females (50 per cent) hearing only breeding females laid eggs than females (8 per cent) isolated from breeding females and males. The differential effects of the stimuli are discussed.     

Sexual signal loss,pleiotropy, and maintenance of a male reproductive polymorphism in crickets

Pleiotropy between male signals and female preferences can facilitate evolution of sexual communication by maintaining coordination between the sexes. Alternatively, it can favor variation in the mating system, such as a reproductive polymorphism. It is unknown how common either of these scenarios is in nature. In Pacific field crickets (Teleogryllus oceanicus) on Kauai, Hawaii, a mutation (flatwing) that segregates as a single locus is responsible for the rapid loss of song production in males. We used outbred cricket colonies fixed for male wing morph to investigate whether homozygous flatwing and normal-wing (wild-type) females differ in responsiveness to male calling song and propensity to mate when paired with either a flatwing or normal-wing male in the presence or absence of courtship song. Flatwing females were less likely to mount a male than normal-wing females. Females of both genotypes showed a preference for normal-wing males and were more likely to mate in the presence of courtship song; normal-wing females were particularly likely to mate with song. Our results show that negative pleiotropy between obligate male silence and female mating behavior can constrain the evolution of sexual signal loss and contribute to the maintenance of a male reproductive polymorphism in the wild.     

The influence of environmental quality on sexual selection in Nauphoeta cinerea (Dictyoptera: Blaberidae)

We examined the impact of environmental conditions on the sexpheromone and mating behavior of the cockroach, Nauphoeta cinerea.Previous research on this species has shown that female behaviorduring courtship reflects female mate choice, male behaviorcorrelates with male social status, and the male sex pheromoneis the character used by females to assess males. In the presentstudy, males and females were allowed to develop from adultemergence to sexual maturity in either a high- or low-qualityenvironment. The environment affected the quantities of sexpheromone components. We found significantly less 3-hydroxy-2-butanoneand 4-ethyl-2-methoxyphenol, but not 2-methylthiazolidine, inthe pheromone glands of males from a poor environment. Pheromonequality was also affected; the ratios involving 2-methylthiazolidinewere altered, while the ratio 3-hydroxy-2-butanone to 4-ethyl-2-methoxyphenoldid not change. Development to sexual maturity under these environmentalconditions also influenced male and female sexual behavior.Male courtship activity reflected environmental influences;males from the low-quality environment took longer to initiatecourtship and spent more time copulating with females from allenvironments. Male quality, as assessed by females, was alsoaffected by their environment. Females were slower to respondto the courtship of males from the poor environment, regardlessof the females' own rearing environments. However, females fromthe low-quality environment also took longer to respond to thecourtship, and required more courtship, regardless of the males'rearing environments. Thus, poor environments also increasefemale choosiness. However, there was only one significant interactionterm, suggesting that the environmental effects are generaland that females do not show adaptive plasticity in mate choice.Studies of sexual selection that consider the effects of variableenvironments on behavior as well as the sexually selected morphologyin other systems are likely to provide new insights into thisevolutionary process     

Sand goby (Pomatoschistus minutus) males exposed to an endocrine disrupting chemical fail in nest and mate competition

Endocrine disrupting chemicals (EDCs) are a widely studied group of chemicals that interfere with the endocrinology of organisms. So far, few studies have demonstrated the effect of EDCs on the reproductive behavior of aquatic wildlife. Here we show that sand goby males' (Pomatoschistus minutus) success in mating competition greatly decreases after an exposure for 7 to 24 days to 17α-ethinyl estradiol (EE2, measured concentration 4 ng L^− 1). The sand goby exhibits a polygynous mating system with male parental care, in which males compete for nest sites and females. The aim of this study was to test how EE2 exposure affects the ability of males to compete for breeding resources, i.e. nest sites and mates. First, EE2 exposed males competed over a nest site against a non-exposed, control male of the same size. Secondly, we examined male courtship behavior and female mate preferences for EE2 exposed males and similar-sized non-exposed, control males. In addition to the behavioral experiments we determined the zona radiata protein (Zrp) mRNA gene expression and measured morphometric indicators of sexual maturation. Our study revealed that EE2 treated males were not able to acquire or defend a nest site. Additionally, EE2 treated males spent significantly less time in active courtship and nest leading behavior than control males. As a result, females clearly preferred to mate with control males. However, we found no significant differences in Zrp mRNA expression or the morphometric indicators between treatments. Our study illustrates that exposure to this EDC can greatly reduce the chances of an individual reproducing successfully. Moreover, it demonstrates that severe behavioral effects can be seen before any effects are detectable at the molecular or morphometric level.     

Early Administration of 17β-Estradiol Partially Masculinizes Song Control Regions and α2-Adrenergic Receptor Distribution in European Starlings (Sturnus vulgaris)

The vocal control system in many songbird species is a sexually dimorphic neural circuit that mediates learning and production of song. The mechanism by which this system is sexually differentiated has been investigated in only one species, the zebra finch (Taeniopygia guttata). Estradiol may be involved in the sexual differentiation of this system, as female zebra finches treated with estradiol as nestlings develop a male-like song system; however, blocking estradiol action in embryonic and nestling male zebra finches does not demasculinize the song system. Therefore, the role of estradiol in song system development is unclear. The role of estradiol in song system sexual differentiation was assessed in European starlings (Sturnus vulgaris). This species is of potential interest because it is less extreme in the degree of sexual dimorphism of the song system and song behavior than zebra finches. While in the field, starling nestlings were implanted with 500 μg of estradiol at 3 days of age. These birds were brought into the laboratory at Day 11 and hand-reared. In females, estradiol produces significant increases in the volumes of song control regions defined by Nissl stain, as well as by autoradiography for α₂-adrenergic receptors; however, these estradiol-treated females have song systems that more closely resemble those of control females than control males. Estradiol-treated males exhibit significant hypermasculinization at 210 days of age, but this effect is transient and hypermasculinization is no longer evident at Day 345. The role of estradiol in sexual differentiation of the neural circuit mediating song behavior remains enigmatic.