Courtship Season Research Articles

Tutoring new song elements to male birds in the wild

Many vocalisations of songbirds are sexually selected and socially learnt behavioural traits that are subject to cultural evolution. For cultural inheritance, it is required that individuals imitate the song elements and build them into their repertoire, but little is known about how such learning mechanisms take place in natural populations of birds with large repertoire size. Using a Hungarian population of the collared flycatcher (Ficedula albicollis) as a model, we tested how often adult males can build new song elements (artificially modified or originated from distant populations) into their repertoire during mating season by using a playback approach. We predicted that when individuals incorporate new elements into their repertoire, the formerly unfamiliar elements from the playback songs would be recovered in the recorded songs of the focal males. We performed a teaching procedure with 26 males, in which we played back song sequences containing three artificially modified and three foreign syllables for each male. We recorded the song of the focal males twice a day for 2–6 days long. Then, we applied a thorough search based on a combined automatic and manual identification method to detect the tutorial syllables in the recorded songs. We found one foreign syllable type in the recordings from one male which indicates that male collared flycatchers may learn new syllable types in the courtship season. As our study has some limits, we highlight some general challenges concerning the use of playback approaches in the field for demonstrating the incidences of learning of particular song elements.

PROTEOMIC AND UTR ANALYSES OF A RAPIDLY EVOLVING HYPERVARIABLE FAMILY OF VERTEBRATE PHEROMONES

During the annual mating season, the mental gland of male plethodontid salamanders diverts its protein synthesizing capacity to the production of courtship pheromones that increase female receptivity. Plethodontid modulating factor (PMF), a highly disulfide-bonded 7-kDa pheromone, shows unusual hypervariability with each male expressing >30 isoforms. Twenty-eight PMFs were purified and matched by proteomic analyses to cDNA sequences. In contrast to coding sequence hypervariability, the untranslated regions (UTRs) show extraordinary conservation, no predicted microRNA binding sites, and an overlapping triplet polyadenylation signal. Full-length cDNA sequencing revealed three PMF gene classes containing subclasses of clustered sequences that support ≥ 13 PMF gene duplications. The unusual phenomena of hypervariable coding regions embedded within extremely conserved UTRs is proposed to occur by a disjunctive evolutionary process. During the short courtship season, the UTRs are hypothesized to subsume and coordinate the transcriptional and translational regulatory mechanisms of the mental gland. PMF, as a secreted protein with limited metabolic feedback in the male, is under minimal mutational restraint and thus has experienced highly accelerated rates of evolution. Consequently, plethodontid salamanders may provide a unique model for furthering our understanding of the selective forces that determine differential rates of gene duplication and evolution in protein families.

Bowers of the Great Bowerbird (Chlamydera nuchalis) remained unburned after fire: is this an adaptation to fire?

Fire plays an important role in the evolution of life-history characteristics of organisms living in fire-prone regions. Although there are many reports of plants exhibiting adaptations to reduce the harmful or lethal effects of fire, little is known about fire-resistance mechanisms among animals, other than fleeing responses. Here, we report observations that may represent a type of fire adaptation in a bird species: bowers in one population of the Great Bowerbird Chlamydera nuchalis remained unburned after fire. If a bower is destroyed by fire or other mechanisms during courtship and breeding season, the male may lose the opportunity to mate with females, thereby reducing his apparent fitness. Therefore, traits that minimise the damage to bowers from fires may be beneficial. By measuring the unburned areas surrounding bowers after fires, we showed that the survival of bowers after fires is unlikely to be solely related to chance. Our observations are consistent with the hypothesis that bower resistance to fire is an adaptation of the Great Bowerbird. However, it is also possible that unburned bowers are by-products of sexual selection.

Testosterone and its effects on courtship in golden-collared manakins ( Manacus vitellinus): Seasonal, sex, and age differences

Male golden-collared manakins gather on leks and perform an acrobatic display to attract females. In temperate breeding species, testosterone (T) activation of courtship displays has been well studied. Few studies have examined T activation of displays in tropical species; even fewer have explored the activational role of T in elaborate courtship displays such as in the manakin. In some tropical species, including manakins, territorial aggression or song behavior are uncoupled from T. We have previously shown that T activates display behavior in manakin males when endogenous T levels are low in the non-courtship season. To understand how T functions in breeding birds, we examined T levels in a large group of manakins sampled during the courtship and non-courtship season. In addition, during the courtship season, we gave T implants to adult males, juvenile males, and females. We found that T levels were low during the non-courtship season and comparatively higher on average during the courtship season. However, T levels were low in many adult males during the courtship season, especially when compared to temperate breeding species. Regardless of initial endogenous T levels during the courtship season, T implants did not increase the display frequency of adult males. T-treated females and juvenile males did display under similar conditions. Our data suggest that the effects of T on manakin display vary with season, sex, and age and that high T is not necessary for display.

Food Transfer in Montagu's HarrierCircus pygargusDuring Courtship

Male Montagu's Harriers delivered prey to their mates by ground and aerial transfer. Between 1992 and 1995, 365 cases of food pass behaviour were recorded (0.47 transfer per observation hour) on calcareous marshes near Chełm in eastern Poland. All of them were observed inside the territory. Ground transfer was dominant at the beginning of the pre-laying period during the time of pair formation. In the courtship season 107 ground transfers (29%) were observed (0.2 per hour). Aerial transfers were observed in 258 cases (71%, 0.41 per hour). The efficiency of aerial food pass was 98% (only five passes ended in the loss of food), that of ground transfer was 100%. Food transfer was strongly correlated with copulation, especially after ground transfer. The number of ground transfers of food was correlated with average time of sky-dancing in males.

An alternative hypothesis for the primary function of a proposed mate assessment behaviour in red-backed salamanders

Using a laboratory experiment, we tested the hypothesis that faecal inspection and squashing behaviours by female red-backed salamanders, Plethodon cinereus, function in a context other than mate assessment, in this case foraging. Because only female P. cinereus squash faecal pellets, other studies have hypothesized that the faecal squashing is a mate assessment behaviour. During the courtship season, we exposed gravid female P. cinereus maintained on a ‘high-quality’ or ‘low-quality’ diet, to the faecal pellets of male and female conspecifics fed ‘high-quality’ diets. Female diet had no effect on activity level, and, overall, P. cinereus showed greater interest in male-marked substrates than female-marked substrates. However, female diet had a large effect on faecal inspection and squashing behaviours, and females showed similar inspection and squashing rates towards both male and female faecal pellets. These results suggest that faecal squashing does not function primarily in mate assessment, but rather as a means for female P. cinereus to gain information about prey availability. We propose that male P. cinereus have evolved to exploit female faecal inspection and squashing behaviours (sensory exploitation) to attract foraging females into areas to increase male encounter rates with females.

The Courtship Season: Love, Race, and Elite African American Women at the Turn of the Twentieth Century

The Courtship Season: Love, Race, and Elite African American Women at the Turn of the Twentieth Century

Sexual coercion in a territorial salamander: females punish socially polygynous male partners

Sexual intimidation (sensu Smuts & Smuts 1993, Advances in the Study of Behavior, 22, 1–63) occurs when members of one sex aggressively ‘punish’ members of the other sex that refuse to mate with them or that merely associate with other individuals of the opposite sex. We examined Clutton-Brock & Parker's (1995, Animal Behaviour, 49, 1345–1365) concept that while males of many species use punishment (intimidation) to coerce females into social or even mating monogamy, such behaviour by females towards males should be rare. However, females in some species are territorial, and aggressive, and thus they may play an active role in sexual intimidation. We tested this proposition in laboratory experiments with territorial red-backed salamanders, Plethodon cinereus, that had been found as single (nonpaired) individuals and in male–female pairs (we term members of a pair ‘partners’) in the forest. We manipulated paired males such that they either had associated with another female before returning to their female partners (socially polygynous) or had not (socially monogamous). In addition, we manipulated single males such that they either had associated with another female before encountering a focal female for the first time (socially polygynous) or had not (socially naı̈ve). During the autumn courtship season, females were significantly more aggressive (threat displays and biting) towards socially polygynous partners relative to those that were socially monogamous. In addition, females spent significantly less time touching socially polygynous partners relative to socially monogamous partners. However, females that met a male for the first time did not differ significantly in their behaviour towards socially polygynous and naı̈ve males. During the late spring, females displayed no behavioural differences towards either male partners or strangers. Thus, female aggression was context dependent, with increased aggression directed only towards polygynous partners and only during the autumn. We infer that females attempt to control social polygyny by partners through aggression during the courtship season but that this coercion ceases in the spring when the females are preoccupied with searching for nest sites for brooding their eggs.

Associations of Male Red-Backed Salamanders with Tail-Intact versus Tail-Autotomized Females during the Courtship Season

Associations of Male Red-Backed Salamanders with Tail-Intact versus Tail-Autotomized Females during the Courtship Season

Associations of Male Red-Backed Salamanders with Tail-Intact versus Tail-Autotomized Females during the Courtship Season

Associations of Male Red-Backed Salamanders with Tail-Intact versus Tail-Autotomized Females during the Courtship Season

Reproductive Signals of Female Lizards: Pattern of Trait Expression and Male Response

AbstractRelative to the volume of studies concerning the function and evolution of male‐biased sexually dimorphic traits, instances of female‐biased sexual dimorphisms remain largely unstudied, especially in species with conventional sex roles. I investigated the signal function of a female‐specific ornamental trait using the striped plateau lizard (Sceloporus virgatus, Phrynosomatidae) as a model system. During the reproductive season, female S. virgatus develop orange color on their throats that is absent in conspecific males. I established the relationship between color expression and female reproductive state, and determined male response to female color. I show that dynamic changes occurring within the color patch can potentially identify each stage of the female reproductive cycle, largely because of a lag in patch growth relative to color intensification. Sexual receptivity is associated with intense patches rapidly growing in size; ovulation occurs near peak color expression; and the unreceptive period is associated with large patches fading in intensity. Because females express orange color during both the receptive and unreceptive periods, the pattern of color expression is consistent with the courtship‐stimulation and courtship‐rejection hypotheses of signal function. Males may preferentially associate with females that have more highly developed color patches during the courtship season, and/or ignore such females when they are unreceptive. An examination of male behavior towards unfamiliar females indicates that female color has a role in courtship stimulation but has little, if any, role in courtship rejection. During the pre‐mating season, males maintained significantly closer affiliation with, and tended to perform more social behavior towards females with more intense color. During the post‐mating season, female color had no apparent effect on male behavior. The evolution and current function of female ornaments may vary among taxonomically‐related species as a result of differences in ecology, social system, and life‐history.

Sexual coercion in a territorial salamander: males punish socially polyandrous female partners

Clutton-Brock & Parker (1995, Animal Behaviour, 49, 1345–1365) proposed that sexual coercion is a third component of sexual selection, along with intrasexual competition for mates and intersexual mate choice. They stated that sexual coercion occurs when males subject females to forced copulation, harassment, or intimidation, and that aggression towards females may occur even when females merely associate (not mate) with other males. We tested this proposition in laboratory experiments with red-backed salamanders, Plethodon cinereus, that had been found in male–female pairs (we call members of a pair ‘partners’) and as single (nonpaired) individuals in the forest. We manipulated paired females so that they either had associated with another male (socially polyandrous partners) or had not associated with another male (socially monogamous partners) before returning to their partners' territories. We also manipulated single females so that, upon encountering a single male for the first time, they either had associated with another male (socially polyandrous strangers) or had not associated with another male (socially naı̈ve strangers). Males were significantly more aggressive towards and stayed farther away from female partners that were socially polyandrous relative to those that were socially monogamous, during both the summer noncourtship season and autumn courtship season. Socially polyandrous females increased escape behaviour relative to socially monogamous females. However, males that met females for the first time did not differ significantly in aggression towards or distance from them when those females were either socially polyandrous or naı̈ve, during both the noncourtship and courtship seasons. Thus, male aggressive behaviour was context dependent, with enhanced aggression only towards partners that were socially polyandrous. We infer that males attempted to manipulate female partners into social monogamy by increasing aggression towards socially polyandrous partners. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Reproductive Biology of Male Eastern Garter Snakes (Thamnophis sirtalis sirtalis) from a Denning Population in Central Wisconsin

Reproductive behavior of the eastern garter snake (Thamnophis sirtalis sirtalis) was evaluated in the field at the Mosquito Hill Nature Center, New London, Wisconsin. In addition, twenty-eight males (24 adult; 4 subadult) were collected during the active season to examine the reproductive physiology. Courtship behavior and mating in this population was similar to previous reports on Thamnophis with the exception of a relatively abbreviated courtship season lasting only 3–5 d. Our study population exhibited a dissociated reproductive pattern in which spermatogenisis was initiated after the breeding season had ended and sperm over wintered in the vas deferens. Upon emergence from low temperature dormancy, the testis mass and seminiferous tubules were regressed with spermatogonia the dominant cell type. Maximum tubule and epithelial development occured in late summer corresponding to peak spermatogenesis and elevated testosterone levels (T). While the tubule diameter and epithelial height of the renal sexual segment (RSS) did not exhibit seasonal fluctuation, sexual granules within the cells of the epithelia did display a seasonal variation that was determined by the absolute number, individual granule density and staining properties. Testosterone levels (T), elevated in the fall before entering winter dormancy, were not significantly different from the levels of animals sampled immediately upon emergence. There was, however, a significant reduction in circulating T in animals sampled following the end of the breeding season. Four small males collected in mid-to-late summer had just initiated spermatogenesis. Examination of the caudal vertebrae by skeletochronology revealed these individuals were in their second active season. In these subadults, development of the testes and RSS development was not as advanced as that of adult males collected at the same time. In addition, the level of circulating T in the subadults was significantly lower than in adults collected at the same time.

Social monogamy in a territorial salamander

Social monogamy, which does not necessarily imply mating or genetic monogamy, is important in the formation of male–female pair associations. We operationally define social monogamy as occurring when two heterosexual adults, exclusive of kin-directed behaviour, direct significantly less aggression and significantly more submission towards each other, and/or spend significantly more time associating with each other relative to other adult heterosexual conspecifics. Long-term pair associations (i.e. those lasting through a lengthy breeding season) that are characteristic of social monogamy are common in some taxa but are virtually unknown in amphibians. Recent studies, however, have suggested that red-backed salamanders,Plethodon cinereus , have complex (for amphibians) social systems. Our laboratory experiments tested the hypothesis that red-backed salamanders found in pairs in the forest display behaviours consistent with social monogamy. During the summer noncourtship season, newly collected male–females pairs showed no preference to associate with their partners more than with a novel conspecific of the opposite sex. However, during the autumn courtship season, paired males and females significantly directed preferential behaviours towards their partners rather than towards a surrogate or a novel paired salamander. Focal animals showed no significant preferences when presented with their partner and a novel single salamander, but they never directed preferential behaviours towards a novel salamander (whether paired or single) or a surrogate. These results are the first to suggest that a salamander species engages in social monogamy. Furthermore, our results suggest that social monogamy may not inhibit paired males and females from displaying alternative strategies: preferring partners when extrapair associations may be disadvantageous (i.e. the extrapair animal is already paired) but not preferring partners when extrapair associations may be advantageous (i.e. the extrapair animal is single).

Defense of Territories by Male-Female Pairs in the Red-Backed Salamander (Plethodon cinereus)

Both adult males and females of the Red-Backed Salamander (Plethodon cinereus) maintain feeding territories under cover objects (rocks and logs on the forest floor) during the summer noncourtship and autumn and spring courtship seasons. Previous research found that, during the summer, 28% of the adults occurred as male-female pairs under cover objects, whereas male-male and female-female pairs rarely occurred. Therefore, we tested the hypothesis that male-female pairs codefend territories against intruders during the courtship season and that such codefense extends into the noncourtship summer. During October 1996 and June 1997, we collected male-female pairs, single males, and single females at Mountain Lake Biological Station, Virginia. In laboratory experiments, we employed six randomized treatments during the courtship season (n = 27 pairs) but only the first two treatments during the noncourtship season (n = 29 pairs). The treatments were the male-female pair confronting (1) a single male intruder and (2) a single female intruder, the male resident alone confronting (3) a single male intruder and (4) a single female intruder, and the female resident alone confronting (5) a single male intruder and (6) a single female intruder. During the courtship season, intruding males did not spend significantly different amounts of time on territories defended by a male-female pair versus territories defended by a single salamander (male or female) from the pair. However, during the courtship season intruding females did spend significantly less time on territories defended by a male-female pair versus territories defended by a single salamander (male or female) from the pair. Male and female intruders spent significantly less time on territories defended by a pair during the courtship season compared to the noncourtship season. During both the courtship and noncourtship seasons, males in pairs spent significantly more time in aggression toward intruding males than did their female partners, and females in pairs spent significantly more time in aggression toward intruding females than did their partners. Thus, our experiment suggests that male-female pairs as residents can codefend territories but not in a cooperative manner. Because paired male residents were more aggressive to male intruders, whereas paired female residents were more aggressive to female intruders, we suggest that males in pairs may not be willing to pass up future polygynous relationships, and females in pairs may not be willing to pass up future polyandrous relationships.

Sequential mate choice by multiply mating smooth newts: females become more choosy

In some species, females sequentially mate with different males within a single mating period, store sperm until the eggs are eventually fertilized, and gain no other resources from the males. Halliday hypothesized that, for such species, a female could ensure fertilization of her eggs by mating with the first male that she encounters; thereafter, she can maximize the quality of her progeny by sampling further males and by mating only with males of higher quality than previously mated males. This hypothesis predicts that females' choosiness will increase as the breeding season progresses. We tested this prediction of Haffiday's hypothesis by examining mate choice by female smooth newts (THturui vuigaris vuigaris). Males of this species develop a dorsal crest during the courtship season. Crest height varies between males and is potentially an indicator of male quality. Initially, female smooth newts were equally willing to mate with males with low or high crests. However, in their second mating, females remated only with high-crested males. These results support our prediction and are consistent with HaOiday's hypothesis. If crest height in smooth newts is an indicator of quality, this change in females' mate choice criterion allows females both to initiate egg-laying very early in the season and, subsequently, to mate preferentially with higher quality mates. Kty toords: female choice, multiple mating, sequential mate choice, sexual selection, smooth newts, THturui vuigaris. [Behav Ecd 8:162-166 (1997)]

Seasonal variation of territory size with the Little Owl (Athene noctua).

In a population of Little Owls (Athene noctua) at the Lower Rhine (FRG), the factors were studied that influence the size and shape of territories of this non-migrating, all-year territorial owl species. These studies were carried out between September 1984 and June 1987. The birds were individually marked with transmitter packages so that their locomotional movements could be monitored. Using a standard protable stimulus (a dummy with an attached loudspeaker) the territorial boundaries of 19 male Little Owls were surveilled during the different seasons of the year. Male Little Owls defended their territories in all seasons, but distinct seasonal changes of intraspecific aggressiveness and territory size were observed. The seasonal variations of territory size followed a common pattern in all studied Little Owls, in spite of individual differences in the size of the defended areas. The largest territories were defended in March/April during the courtship season [Formula: see text]. In May/June all male Little Owls reduced the size of their territories [Formula: see text]. This corresponds to the breeding and nestling period. The yearly minimum of territory size [Formula: see text] was reached in the summer months July and August when the fledglings were still fed in the parental territory. When the first-year birds started to disperse in autumn (September/October), the size of the defended areas of the adult tenants again increased [Formula: see text]. In winter (November to February), a further increase in territory size was observed for periods of warm weather [Formula: see text]. Male Little Owls, however, were less aggressive during winter than in the following courtship season. On cold winter days with a ground cover of snow territorial aggressiveness ceased. Pastures and meadows offered a continuous food supply almost throughout the year. In some seasons they were overproportionally represented in the territories of Little Owls compared to the general surroundings. In reaction to changing accessibility of food, the hunting ranges within the home ranges were shifted much faster than the boundaries of the defended territories. The significance of various factors contributing to the variability of territory size in Little Owls are discussed (e.g. availability of food, seasonal and individual differences in aggressiveness, experience in the occupied area, population density).

Control of length of the courtship season in the red-sided garter snake, Thamnophis sirtalis parietalis: the role of temperature

The influence of temperature on the length and intensity of the courtship season was examined in both field and laboratory populations of red-sided garter snakes (Thamnophis sirtalis parietalis) over a 2-year period. Snakes were exposed to fluctuations in temperature following emergence from hibernation and activation of courtship behavior. In the field, males were exposed to four temperature regimens: extended hibernation (0L:24D, 4 ± 1.5 °C), cool (14L:10D, 12 ± 2.3° C), warm (14L:10D, 28 °C:ambient), or control (ambient temperatures and light). Control animals exhibited courtship behavior fluctuating in intensity with daily ambient temperatures. Animals exhibited high intensity courtship behavior when exposed to warm conditions following emergence from either natural hibernation or a secondary period of laboratory hibernation. Animals placed in the cool regimen were active but exhibited very little courtship behavior. Animals maintained under the cool regimen for 14 days did not initiate courtship behavior when placed in the warm regimen. Studies conducted in the laboratory support the field results. However, whereas animals maintained under the cool regimen for 14 days and then placed in the warm regimen exhibited dramatically reduced courtship behavior, animals placed in the warm regimen after 21 days under the cool regimen initiated courtship of normal intensity and duration. Following the end of all courtship behavior, males exposed to conditions of hibernation for a brief period reinitiated courtship behavior. These data suggest that the areas of the central nervous system critical for the perception of temperature fluctuations and initiation of courtship behavior remained sensitive in late spring. Following the end of the courtship season, females exposed to a brief period of hibernation also reinstated courtship behavior in noncourting males. These data suggest that the length of the courtship season ultimately may be controlled by the presence of attractive females.

Annual reproductive cycle in the male red-sided garter snake, Thamnophis sirtalis parietalis: Field and laboratory studies

The reproductive cycle of male red-sided garter snakes ( Thamnophis sirtalis parietalis) was studied in a laboratory-maintained population and in nature. Both populations exhibited a dissociated reproductive pattern in which spermatogenesis was initiated after the breeding season and sperm were stored in the vas deferens over winter. Although animals in both the laboratory and the field exhibited a dissociated reproductive pattern, temporal differences were evident in the two populations. Animals maintained in the laboratory initiated and completed spermiation much sooner than animals collected in the field. In the captive population, the renal sexual segment (RSS) could be identified but did not exhibit a seasonal fluctuation, indicating perhaps that androgen production was continuous, but at a reduced level. In nature, the RSS was hypertrophied at emergence, regressed following the breeding season, and again hypertrophied as circulating androgens increased in the fall, prior to hibernation. In both laboratory-maintained and field animals the circulating concentrations of testosterone and dihydrotestosterone at emergence were initially similar to the levels observed prior to hibernation but by 2 weeks postemergence had decreased to a relatively low level. Both the high androgen levels prior to hibernation and the rapid decrease during the spring courtship season may result from temperature influences on clearance rates. Plasma levels of corticosterone varied during the spring, first increasing upon emergence and then declining approximately 2 weeks following emergence.

Einfluß der Konzentration der Zuckerlösung auf den Gesang und das Balzverhalten des Gelbbauchnektarvogels (Nectarinia venusta)*

Different concentrations of a sucrose solution vary the courtship song and behaviour of the male yellow-bellied sunbird Nectarinia venusta- the duration of subsong, total singing duration, and the absolute number of full song phrases. With high concentrations the sunbird sings more full song phrases but less subsong during the courtship season than otherwise. The various effects are described.