Effects of the antiandrogen cyproterone acetate on reproduction in male and female ring doves

The present experiment was designed to study the role of increased plasma androgens which are seen in male and female doves during courtship. In pairs of doves either the male or female was injected daily with oil or with 6 or 15 mg of cyproterone acetate (CA), starting 3 days before pairing. Cyproterone acetate at both dose levels reduced the amount of bow-cooing shown by the male on the day of pairing, and at the higher dose resulted in a reduction of nest soliciting by injected males and their untreated mates over the 7 days of testing. At the high dose only, the size of the testes was reduced. In pairs where females received CA, there was a decrease in levels of nest soliciting by both partners and ovarian development was blocked. The results are discussed in terms of the possible significance of fluctuating androgen levels found in doves during the prelaying period.     

Do Female Red-winged Blackbirds Engage in a Mixed Mating Strategy?

Parentage analyses of broods of nestling red-winged blackbirds (Agelaius phoeniceus) revealed that extra-pair fertilizations (EPFs) accounted for 24% of the offspring. 8% of attempted copulations and 13% of male courtship displays during observations of focal females were by extra-pair males. In addition, mates and non-mates often chased and occasionally made physical contact with females; 34% of those chases in which contact was made were extra-pair chases. Females behaved variably during both within-pair and extra-pair events; females crouched less and resisted more frequently during extra-pair courtship than during within-pair courtship. All extra-pair events, whether natural or induced by male removal, were either resisted or accepted by the female. In 318 focal female-hours of observation during the fertilizable period, no female was ever seen in another male's territory soliciting a copulation. In addition, removal of females' mates resulted in frequent extra-pair courtship and copulation; all of these occurred on the removed male's territory. Some females left their mates' territories on occasion — these forays were nearly always off the study area, no female was ever seen copulating with an extra-pair male while on these forays, and neither the frequency nor the duration of female forays correlated with the frequency of extra-pair fertilizations within broods. There were no associations between extra-pair fertilizations and female age, settlement order, nest order, or clutch size. The number of fledglings produced from a nest was significantly positively associated with the number of sires of the brood. Fewer offspring apparently starved in broods that were multiply sired, yet males did not provide courtship feedings during either within-pair or extra-pair copulations, nor was any paternal care provided to young sired through extra-pair matings. The frequency of infertile eggs was low (< 1%); in those instances of infertile eggs the territory owner sired some young in the same nest or another nest on his territory. Fewer broods were a mixture of within-pair and extra-pair paternity than expected by chance. Clear evidence implicating a mixed strategy on the part of females could not be gathered. Because females behaved variably and because not all costs and benefits to females of extra-pair copulations could be measured, it remains possible that female behavior patterns are either (1) part of a mixed strategy, or (2) part of a strategy minimizing the costs of copulation.     

The effect of an androgen inhibitor on behavior and testicular morphology in the stickleback Gasterosteus aculeatus

It is generally held that the decline in courtship which is seen at the beginning of incubation during the reproductive cycle of the male ring dove (Streptopelia risoria) is the result of changes in endocrine secretion rather than changes in response to the external situation. To test this hypothesis, male ring doves proceeding through a cycle with their mates were tested at selected intervals to determine whether there was a decline in courtship behavior in the course of a reproductive cycle. Four conditions were examined. Inexperienced and experienced males were tested with a stimulus female in two situations; once after the mate and nest were removed from the home cage, and once after the mate only was removed. In the former situation the male courted a stimulus female irrespective of the stage of the cycle he had reached with his mate. In the latter situation, as incubation with the mate progressed, males continued to incubate when the stimulus female was introduced. Thus, the male's display of courtship during the reproductive cycle is influenced by the external stimulus situation presented by the female and the nest.     

Plastic sex-roles in the common goby – the effect of nest availability

One of the most important factors shaping animal sex-roles is the operational sex ratio, since a skew of this ratio promotes mating competition in the more abundant sex. In this study, we wanted to see if a change in sex-roles, related to an environmental induced change in operational sex ratio, could be demonstrated in a field situation. Common goby ( Pomatoschistus microps ) males build nests under bivalve shells and provide exclusive parental care. Therefore, available nest sites are crucial for successful breeding in this species and should also affect the operational sex ratio. We addressed the question of whether the availability of nest sites, through an effect on the operational sex ratio, affects courtship and mating competition in the common goby. We increased nest site availability in the field by adding potential nest material (bivalve shells) to one location. We then compared the reproductive behaviour of the gobies at this and another location with lower nest site abundance. In general, the reproductive behaviour differed as predicted. Under nest shortage, males occupied new nests and received eggs faster than under nest excess. Behavioural observations of nests revealed that males initiated courtship more often than females where nest sites were abundant, whereas female courtship dominated where nests were scarce. Males more often rejected females attempting to enter their nests under nest shortage, male sneaking attempts were also more common in this bay. Male-male aggression was frequent at both locations, whereas agonistic interactions between females only occurred in the nest shortage bay. Thus, males should be subject to sexual selection in both bays even though courtship roles differed. These results suggest that nest site availability affects mating competition and courtship roles in the common goby.     

Antiphonal duetting and sex hormones in the tropical bush shrike Laniarius funebris (HARTLAUB).

We investigated changes in antiphonal duetting with phases of reproduction and circulating levels of luteinizing hormone, testosterone, and estradiol in slate-colored boubous (Laniarius funebris) breeding in aviaries. Frequency of overall male singing did not vary with reproductive phase while frequencies of female singing and female vocal responses to male song were reduced during incubation and feeding of nestlings. This resulted in significant changes in frequency of duetting. Males sang the sexual song type M1 more often during courtship and nest building than during the nestlings phase. Their territorial song types M2 and M4 did not vary with breeding phase. Females were less responsive to M1 during incubation and to M2 during the nest building and nestlings than during the courtship phase. Plasma levels of luteinizing hormone and testosterone increased in males from the prebreeding to the courtship phase. While testosterone decreased already during nest building and remained low during subsequent phases of reproduction, luteinizing hormone decreased during incubation and feeding of nestlings. Female luteinizing hormone levels were highest during nest building. Female estradiol levels decreased from nest building to incubation and increased again during subsequent nest building. Female testosterone levels were low but not basal and did not vary with phase. Neither the overall male and female singing frequencies nor the frequencies of male song types were correlated with hormonal state. However, female participation in territorial duets M4 correlated positively with their testosterone levels. It is suggested that in this monogamous, duetting species with prolonged pairbonds behavioral cues between the mates are more important than the hormonal state in control of male and female singing.     

Nest ornamentation by female spotless starlings in response to a male display: an experimental study

1. The use of behavioural traits by females in signalling condition has been practically ignored in evolutionary theory. However, females may also exhibit ornaments and behavioural displays, although less elaborated than those of males. 2. In this study we suggest that the carrying of feathers by spotless starlings Sturnus unicolor Temminck females to decorate the nest represents an elaborated and costly behaviour that is displayed in response to a courtship male behaviour: the carrying of nest green plants. 3. By experimentally increasing the amount of green plants in the nests, to give the appearance that highly attractive males defended them, we induced females to increase their feather carrying rates. 4. The amount of feathers carried to the nest was correlated to female reproductive experience and laying date, two variables correlated with female body condition. These results suggests that this behaviour may work as an honest indicator of female quality. 5. We conclude that male carrying plants and female carrying feathers can be viewed as two sex-specific functionally related signalling behaviours involved in mutual courtship or status signalling.     

Aggression versus courtship in threespine sticklebacks and the role of habituation to neighbours

Interaction of courtship and territorial aggression in male threespine sticklebacks, Gasterosteus aculeatus, was investigated by presenting dummy females to subjects nesting alone (solitary situation) and in view of males nesting in adjacent tanks (rival situation). During dummy presentation subjects engaged in more courtship and nest activity when solitary than when in the rival situation. Behaviour of subjects in the latter situation was dominated by threats and attempts to bite rivals during dummy presentation. Thus, rivals can interfere with another male's courtship by competing for the time during which he could court a female or by eliciting in him an aggressive state that is incompatible with sexual behaviour. Subjects in the rival situation gradually decreased the time spent with rivals but increased the time spent courting the dummy and tending the nest during presentations. This decrease in aggression towards neighbouring males is presumed to result from habituation. Thus, habituation can play an important role in mitigating the aggressive response to familiar rivals, allowing males to devote more time and energy to courtship and nest activities while still forming breeding aggregations in which members may mutually benefit.     

Spawning behavior and interspecific breeding in three japanese greenlings (hexagrammidae)

The spawing behavior ofHexagrammos otakii. H. octogrammus andH. agrammus was observed in two different regions of northern Japan using underwater video cameras placed near nests guarded by males. The spawning behavior of the three species consisted of similar patterns, although body size and nuptial coloration and nest location of territorial maleH. otakii differed from those of the other twoHexagrammos species. The courtship display of territorial males in each species involved rushing, butting and undulation of the trunk. When a female entered the nest, the male leaned his head on the future spawning bed in the nest and spasmodically undulated his trunk. The female that responded to the courtship laid her eggs within the seaweed bed. The territorial male then passed over the eggs, touching his genital pore to the egg mass, and released sperm. Sneaking by other males was frequently observed following the sperm emission. In both regions, females ofH. octogrammus andH. agrammus commonly responded to courtship of maleH. otakii and mated with them, but not vice versa. Possble reasons for the natural occurrence of such unidirectional hybridization are discussed.     

Courtship versatility in the jumping spider, Phidippus johnsoni (Araneae: Salticidae)

A given male of P. johnsoni has at his disposal two alternative types of courtship. Each consists of distinctly different motor patterns and involves different sensory channels. If the male encounters a female outside her nest, he uses type 1 courtship. Type 2 courtship occurs if the male encounters a female inside her nest. Spiders do not respond to visual stimuli (house flies) under red light. The fact that type 2, but not type 1, courtship occurs when spiders are observed under red light is taken as evidence that type 1 is vision dependent, whereas type 2 is not vision dependent. Selection factors favouring the evolution of courtship versatility are discussed.     

Redescription of Natalaspis leptocarpi n.comb. (Homoptera: Diaspididae)

Abstract

Cyllobelus rufopictus? a salticid species from equatorial Africa, has a large and complex repertoire of displays. These spiders live on and near the ground in habitats of short grass, and build opaque silk nests on dead leaves. Each male uses one of three different mating tactics depending on the female’s maturity and location (communicatory versatility). Type 1 courtship, involving special movements and postures of the legs, palps, and body, occurs if the female is an adult away from the nest; apparently this type of courtship is vision-dependent. If the male encounters an adult female inside her nest, he uses Type 2 courtship, which consists of movements by the male that cause the silk to vibrate. If the female is a subadult inside her nest, the male initially uses Type 2 courtship, then builds a second chamber on the female’s nest, and cohabits until she moults and matures. Other displays occur during male-male and female-female interactions. Biting and pinching are distinctive Type 2 courtship displays that have not been described previously for salticids, and juddering is the most distinctive Type 1 display.     

Seasonal sex role changes in the blenniid Petroscirtes breviceps, a nest brooder with paternal care

The plasticity of the sex roles in the blenniid fish Petroscirtes breviceps , a nest brooder with exclusive paternal care, was studied throughout an 8 month breeding season. Males performed most courtships early and late in the breeding season, whereas females performed most in the middle of the season. These results indicated that the sex of individuals initiating courtship changed seasonally, with courtship role reversal in the middle of the season. Intrasexual aggression in both sexes occurred much more frequently in mid-season than in the early and late seasons. Males frequently fought when available nest sites were limited, regardless of the presence of females, suggesting that males competed for nests in order to qualify to mate (resource competition). In contrast, courting females fought only in mid-season, when females' relative success in entering nests decreased, indicating that females competed for limited mating opportunities (mating competition). The reversed courtship roles and female mating competition in mid-season suggested that the sex roles in P. breviceps changed seasonally from the conventional roles to reversed roles and back again during one breeding season. This study provides the first empirical evidence of multiple changes in the sex roles of animals within a breeding season.     

Males with a Faster Courtship Display have More White Spots and Higher Pairing Success in the Diamond Firetail,Stagonopleura guttata

There is growing evidence that female mate choice could be based on a combination of multiple signals that often involve both ornamental colourful traits and behavioural displays. The Diamond Firetail is an Australian finch with a variable number of white spots on their black flank feathers. The number of white spots is a dimorphic characteristic: females have more spots than males, and males prefer females with many spots. Previously, we found assortative pairing for spot number despite the absence of experimental evidence for female preference for male spot number. Here, we test whether the male behavioural courtship display (bobbing while waving a grass stem) correlates with male spot number and pairing success. We also test whether male spot number predicts the outcome (winner or loser) of intrasexual competition over courtship materials (grass stem, perch, nest site). Males with many spots had higher pairing success, and male spot number correlated with the intensity of courtship display. In a multivariate statistical analysis, male courtship display was the stronger predictor of male pairing success. Finally, male spot number predicted the outcome of intrasexual interactions: males with many spots consistently won contests over grass stems, perches and nest sites. We suggest that intrasexual selection could favour male spot number, whereas courtship intensity appears to be under stronger intersexual selection.     

Male wrens with large testes breed early

To display to females, male wrens, Troglodytes troglodytes, use cock nests built on their territories. Nest building starts about a month before the first females begin egg laying. The timing of nest building is highly variable between males with up to 8 weeks separating the earliest from the latest males to initiate this display activity. Males that weigh more before the breeding season initiate nest building earlier than lighter males. We measured testis size in male wrens in the prebreeding period during which seasonal testicular recrudescence is occurring. The initiation of nest building was predicted by male age and by testis size. This suggests that variation in the start of courtship activity may reflect variation between males in the rate of testicular recrudescence. Variation in male prebreeding body mass was influenced by variation in testis size, which suggests that the relation reported earlier between body mass and timing of nest construction could be explained, in part, by variation in testis size. Alternatively, if body mass reflects body condition then both the extent of testes recrudescence and the timing of courtship activity could be condition-dependent traits. Copyright 2000 The Association for the Study of Animal Behaviour.     

Lesions to the Medial Preoptic Area Affect Singing in the Male European Starling (Sturnus vulgaris)

The aromatization of testosterone (T) in the medial preoptic nucleus (POM) is known to regulate male courtship and sexual behaviors expressed prior to, and in anticipation of, copulation. Singing in male European starlings is used to attract mates prior to physical sexual contact, suggesting that the POM might be involved. The present study was performed to examine the effects of lesions targeting the POM on singing and courtship behavior in reproductively active male starlings. A significant decrease in song output and the gathering of green nest materials was observed in males with lesions to the POM compared to males with damage to brain areas outside of the POM. Lesions did not affect a male's tendency to remain near a female or to occupy a nestbox, suggesting that the effects of POM lesions were specific to courtship behaviors. Behavioral differences were not related to testis mass or volume, and GnRH immunoreactivity was observed within the hypothalamus and median eminence for each male, suggesting that the effects of POM lesions were related specifically to POM involvement in song expression rather than to a disruption of the GnRH axis. These results suggest a general role for the POM in the expression of behaviors related to sexual arousal or anticipation, including song.     

Lesions to the medial preoptic area affect singing in the male European starling (Sturnus vulgaris)

The aromatization of testosterone (T) in the medial preoptic nucleus (POM) is known to regulate male courtship and sexual behaviors expressed prior to, and in anticipation of, copulation. Singing in male European starlings is used to attract mates prior to physical sexual contact, suggesting that the POM might be involved. The present study was performed to examine the effects of lesions targeting the POM on singing and courtship behavior in reproductively active male starlings. A significant decrease in song output and the gathering of green nest materials was observed in males with lesions to the POM compared to males with damage to brain areas outside of the POM. Lesions did not affect a male's tendency to remain near a female or to occupy a nestbox, suggesting that the effects of POM lesions were specific to courtship behaviors. Behavioral differences were not related to testis mass or volume, and GnRH immunoreactivity was observed within the hypothalamus and median eminence for each male, suggesting that the effects of POM lesions were related specifically to POM involvement in song expression rather than to a disruption of the GnRH axis. These results suggest a general role for the POM in the expression of behaviors related to sexual arousal or anticipation, including song.     

Metabolic efficiency in courtship favors males with intermediate mass in the Australian redback spider,Latrodectus hasselti

Recent studies have suggested that metabolic efficiency may be an important factor in male mating success when females require vigorous and/or prolonged courtship. In capital breeding animals in which a male’s resource pool is fixed at adulthood the relationship between energy expenditure and courtship performance may be especially important, as males are expected to utilize their finite resources efficiently when soliciting mates. Males may benefit from being efficient, i.e., achieving a sufficiently high level of courtship signaling at low energetic cost, if it enables them to acquire mates before their limited energy reserves are depleted. We investigated the relationship between metabolic efficiency and courtship vibrational signaling in the Australian redback spider, Latrodectus hasselti, a semelparous capital breeder where males invest heavily in courtship to secure a mating. We assessed metabolic rate in a sample of males and measured two courtship components (duty cycle and amplitude) that reflected the energy content of web-borne vibrations. We then calculated two indices of metabolic efficiency for these courtship properties. There was a quadratic relationship between mass and duty cycle such that the highest duty cycle signals were performed by males having intermediate mass. Furthermore, intermediate-mass males were also the most metabolically efficient. Prolonged courtship is necessary in L. hasselti for successful mating, and the results of this study suggest that intermediate-mass males are superior courters because they utilize their finite resource pool most efficiently to produce high energy vibrational signals.     

Status-appropriate singing behavior,testosterone and androgen receptor immunolabeling in male European starlings (Sturnus vulgaris)

Vocalizations convey information about an individual's motivational, internal, and social status. As circumstances change, individuals respond by adjusting vocal behavior accordingly. In European starlings, a male that acquires a nest site socially dominates other males and dramatically increases courtship song. Although circulating testosterone is associated with social status and vocal production it is possible that steroid receptors fine-tune status-appropriate changes in behavior. Here we explored a possible role for androgen receptors. Male starlings that acquired nest sites produced high rates of courtship song. For a subset of males this occurred even in the absence of elevated circulating testosterone. Immunolabeling for androgen receptors (ARir) was highest in the medial preoptic nucleus (POM) in males with both a nest site and elevated testosterone. For HVC, ARir was higher in dominant males with high testosterone (males that sang longer songs) than dominant males with low testosterone (males that sang shorter songs). ARir in the dorsal medial portion of the nucleus intercollicularis (DM) was elevated in males with high testosterone irrespective of dominance status. Song bout length related positively to ARir in POM, HVC and DM, and testosterone concentrations related positively to ARir in POM and DM. Results suggest that the role of testosterone in vocal behavior differs across brain regions and support the hypothesis that testosterone in POM underlies motivation, testosterone in HVC relates to song quality, and testosterone in DM stimulates vocalizations. Our data also suggest that singing may influence AR independent of testosterone and that alternative androgen-independent pathways regulate status-appropriate singing behavior.     

Courtship Sounds Advertise Species Identity and Male Quality in Sympatric Pomatoschistus spp. Gobies

Acoustic signals can encode crucial information about species identity and individual quality. We recorded and compared male courtship drum sounds of the sand goby Pomatoschistus minutus and the painted goby P. pictus and examined if they can function in species recognition within sympatric populations. We also examined which acoustic features are related to male quality and the factors that affect female courtship in the sand goby, to determine whether vocalisations potentially play a role in mate assessment. Drums produced by the painted goby showed significantly higher dominant frequencies, higher sound pulse repetition rates and longer intervals between sounds than those of the sand goby. In the sand goby, male quality was predicted by visual and acoustic courtship signals. Regression analyses showed that sound amplitude was a good predictor of male length, whereas the duration of nest behaviour and active calling rate (i.e. excluding silent periods) were good predictors of male condition factor and fat reserves respectively. In addition, the level of female courtship was predicted by male nest behaviour. The results suggest that the frequency and temporal patterns of sounds can encode species identity, whereas sound amplitude and calling activity reflects male size and fat reserves. Visual courtship duration (nest-related behaviour) also seems relevant to mate choice, since it reflects male condition and is related to female courtship. Our work suggests that acoustic communication can contribute to mate choice in the sand goby group, and invites further study.     

Interspecific territoriality in males of the tube blenny <Emphasis Type="Italic">Neoclinus bryope</Emphasis> (Actinopterygii: Chaenopsidae)

Territoriality was investigated in the tube blenny Neoclinus bryope (Actinopterygii: Chaenopsidae) at rocky intertidal areas of Banda Beach, Tateyama Bay, central Japan. Males used small holes as spawning nests, usually staying at the nest and maintaining the area while showing exclusive behaviors. Their home ranges were limited to areas within 30 cm distance from the nest for over 2 months. Four heterospecific fishes were threatened when they approached to within 6–14 cm of the nest holes, and two species of carnivorous snails were removed at points 0–30 cm from the nest entrance. There were no significant differences between the distances from the nest entrances to the points defended against fish and those used for foraging. As the four heterospecific species have similar feeding habits to those of N. bryope, the area defended against fishes may function as a foraging territory. At 24 h following the removal of nest owners, carnivorous snails had gathered to actively prey on eggs, indicating that the area defended against snails may function as a territory for protection against egg predators. Although the positions of females where males started courtship displays were significantly farther than the foraging points and the positions of threatened fishes, males displayed no territoriality against conspecific males. The fact that males did not leave the nest hole during the courtship suggests that it may be costly to maintain a courtship territory. These results show that males of tube blenny maintain territories for egg guarding and for protecting food resources around their nest holes in the spawning season.