Social environment during egg laying: Changes in plasma hormones with no consequences for yolk hormones or fecundity in female Japanese quail, Coturnix japonica

Abstract

The social environment can have profound effects on an individual’s physiology and behaviour and on the transfer of resources to the next generation, with potential consequences for fecundity and reproduction. However, few studies investigate all of these aspects at once. The present study housed female Japanese quail (Coturnix japonica) in pairs or groups to examine the effects on hormone concentrations in plasma and yolk and on reproductive performance. Circulating levels of androgens (testosterone and 5-α-dihydrotestosterone) and corticosterone were measured in baseline samples and after standardised challenges to assess the responsiveness of the females’ endocrine axes. Effects of the social environment on female fecundity were analysed by measuring egg production, egg mass, fertilization rates, and number of hatched offspring. Counter to expectation, females housed in pairs had higher plasma androgen concentrations and slightly higher corticosterone concentrations than females housed in groups, although the latter was not statistically significant. Pair vs. group housing did not affect the females’ hormonal response to standardised challenges or yolk testosterone levels. In contrast to previous studies, the females’ androgen response to a gonadotropin-releasing hormone challenge was not related to yolk testosterone levels. Non-significant trends emerged for pair-housed females to have higher egg-laying rates and higher fertility, but no differences arose in egg weight or in the number, weight or size of hatchlings. We propose that our unexpected findings are due to differences in the adult sex ratio in our social treatments. In pairs, the male may stimulate female circulating hormone levels more strongly than in groups where effects are diluted due to the presence of several females. Future studies should vary both group size and sex composition to disentangle the significance of sexual, competitive and affiliative social interactions for circulating and yolk hormone levels, and their consequences for subsequent generations.

Effects of the maternal and current social environment on female body mass and reproductive traits in Japanese quail (Coturnix japonica)

“…This would suggest higher plasma androgen or corticosterone concentrations in group-housed females compared with pair-housed females. However, as we previously found that female Japanese quail housed in pairs had higher circulating androgen levels and tended to have higher circulating corticosterone levels compared with females housed in groups (Langen et al, 2017), we expected that the reverse might also be found.…”

“…P0 females were housed in pairs (one female with one male) or in groups (three females with one male), whereas F1 females were housed in pairs (two females, one offspring from each of the P0 treatments) or in groups (four females, two offspring from each of the P0 treatments). All experiments and testing described for P0 generation females (Langen et al 2017), and for F1 generation females from hatching to the beginning of the experimental social conditions (Langen et al 2018) have been published previously. The birds were placed in the experimental social conditions at the age of 29 days in the P0 generation (see Langen et al, 2017) and 24 days in the F1 generation ( Fig.…”

“…All experiments and testing described for P0 generation females (Langen et al 2017), and for F1 generation females from hatching to the beginning of the experimental social conditions (Langen et al 2018) have been published previously. The birds were placed in the experimental social conditions at the age of 29 days in the P0 generation (see Langen et al, 2017) and 24 days in the F1 generation ( Fig. 1), about 2 weeks before the onset of egg laying.…”

“…In Japanese quail, frequent changes in the group composition of breeding females are thought to reflect increased social densities and lead to elevated plasma corticosterone concentrations (Guibert et al, 2010). In contrast, Japanese quail females housed in pairs had higher circulating androgen levels and tended to have higher circulating corticosterone levels than group-housed females (Langen et al, 2017). Such effects of the social environment on female physiology and body mass and condition may affect their ability to invest in reproduction, resulting in changes in the quality or quantity of eggs produced or the quality or quantity of the offspring (Christians, 2002;Drent and Daan, 1980;Lim et al, 2014;Ronget et al, 2018;Sockman et al, 2006).…”

“…In the present study, we investigated the potential interactive effects of the maternal and offspring social environment in Japanese quail. Females of the parental (P0) generation were housed in pairs (one female and one male) or in groups (three females and one male) and allowed to reproduce (Langen et al, 2017). The females of the offspring (F1) generation were similarly housed in either pairs of two females or groups of four females, with daughters from the two maternal conditions evenly allocated to the two F1 social conditions.…”