Effects of androgens and estrogens on crowings and distress callings in male Japanese quail, Coturnix japonica

Winning and losing in public: audiences direct future success in Japanese quail

Among vertebrates, winning a fight enhances the probability of future victories and vice versa and the role of post-conflict testosterone in mediating this 'winner effect' is widely accepted. In a series of staged fights of Japanese quail (Coturnix japonica) we tested both opponents' pre-fight and post-conflict testosterone, behavior and dominance status after returning to their social groups. We found that the presence of a familiar mixed-sex audience during the encounter modulated both the testosterone response and the long-term success after a fighting experience. 'Public losers' but not 'public winners' lacked a post-conflict testosterone response, whereas without an audience both winners and losers increased testosterone metabolite levels. Long-lasting winner and loser effects exclusively occurred when the performance information was perceived by a mixed-sex audience. In further experiments we manipulated the testosterone responsiveness of either the loser or the winner. An artificial post-conflict testosterone surge after having lost a fight effectively reversed the loser effect in Japanese quail. In contrast, the 'winner effect' was not changed by blocking testosterone after the fight. Overall, male Japanese quails' post-conflict testosterone was connected to the audiences and thus, own or the observers' perception of the challenge rather than to winning or losing a fight.

Long-lasting and sex-specific consequences of elevated egg yolk testosterone for social behavior in Japanese quail

In birds, early exposure to steroid hormones deposited in egg yolks is hypothesized to result in long-lasting effects on brain and behavior. However, the long-term effects of maternal androgens on the development of social behavior, and whether these could interfere with the effects of the endogenous gonadal hormones that mediate sexual differentiation, remain poorly known. To answer these questions, we enhanced yolk testosterone by injecting testosterone (T) in oil into Japanese quail (Coturnix japonica) eggs prior to incubation. Vehicle-injected (V) eggs served as controls. From age 3 weeks to 8 weeks, sexual development was measured using morphological and physiological traits, and social behavior was measured, including male-typical sexual behavior. In females, treatment with testosterone boosted growth. Males from T-injected eggs developed an affiliative preference for familiar females and differed from V-injected males in the acoustic features of their crows, whereas sexual interest (looking behavior) and copulatory behavior were not affected. These long-lasting and sex-specific yolk testosterone effects on the development of dimorphic traits, but without disrupting sexual differentiation of reproductive behavior suggest potential organizational effects of maternal testosterone, but acting through separate processes than the endocrine mechanisms previously shown to control sexual differentiation. Separate processes could reflect the action of androgens at different times or on multiple targets that are differentially sensitive to steroids or develop at different rates.

Embryonic and posthatching treatments with sex steroids demasculinize the motivational aspects of crowing behavior in male Japanese quail

Demasculinizing action of embryonic estrogen on crowing behavior in male Japanese quails was examined. Eggs were treated with either 20 microg of estradiol benzoate (EB) or vehicle on the 10th day of incubation. Chicks hatched from both groups of eggs were injected daily with either testosterone propionate (TP; 10 microg/g b.w.), 5alpha-dihydrotestosterone (DHT, a non-aromatizable androgen; 10 microg/g b.w.), or vehicle from 11 to 50 days after hatching, and during this period their calling behaviors were observed. Irrespective of embryonic treatments, all birds received posthatching treatment with either TP or DHT, but not with vehicle, emitted crows in place of distress calls in a stress (non-sexual) context of being isolated in a recording chamber. The posthatching TP, but not posthatching DHT, induced crowing in a sexual context (crowing in their home-cages) from much earlier age than posthatching vehicle in the birds received control embryonic treatment with vehicle. The same TP treatment, however, completely eliminated the crowing in a sexual context in the birds received EB during their embryonic life. In the birds treated with either posthatching DHT or posthatching vehicle, the crowing in a sexual context was only slightly decreased by embryonic EB treatment. These data suggest that posthatching estrogen, derived from testosterone aromatization, enhances the demasculinizing action of embryonic estrogen, and thus strongly reduces the sexual motivation for crowing behavior. This demasculinizing action, however, would not influence vocal control system which generates acoustic pattern of crowing in the presence of androgens allowing the birds to crow in a non-sexual context.

Sexual Differentiation of the Vocal Control System of Birds

Birds evolved neural circuits of various complexities in relation to their capacity to produce learned or unlearned vocalizations. These vocalizations, in particular those that function in the realm of reproduction, are frequently sexually dimorphic, both in vocal learners (songbirds, parrots, some hummingbirds) and vocal nonlearners (all other birds). In many cases, the development and/or the adult differentiation of vocalizations of sociosexual function is sensitive to sex hormones, androgens and estrogens. The underlying mechanisms have been studied in detail in songbirds, a bird group that comprises about half of all bird species. Next to unlearned calls, songbirds produce learned songs that require forebrain vocal control areas that express receptors for androgens and estrogens. These forebrain vocal areas are sexually dimorphic in many species, but a clear relation between the degree of "brain sex" and sex differences in vocal pattern is lacking, except that a minimum number of vocal neurons is necessary to sing learned songs. Genetic brain-intrinsic mechanisms are likely to determine the neuron pools that develop into forebrain song control areas. Subsequently, gonadal steroid hormones, androgens and estrogens, modulate the fate of these neurons and thus the functionality of the vocal control systems. Further action of gonadal hormones, and may be other factors signaling the sociosexual and physical environment, affect the phenotype of vocal control areas in adulthood. Despite the clear evidence of hormone dependency of both adult vocalizations and phenotypes of vocal neuron pools, their causal relation is little understood.