Abstract
In sex-role-reversed species, females are typically the more competitive sex, defending territories and access to mates, while males take care of the young, often without any help from the female. In males of species with traditional sex roles, testosterone levels generally rise during the breeding season and modulate territorial and aggressive behaviour. Similarly, testosterone may modulate aggressive behaviour in females of sex-role-reversed species. To test this idea, we experimentally increased testosterone levels in sex-role-reversed polyandrous female Barred Buttonquails (Turnix suscitator) by implanting them with testosterone pellets and testing their behavioural responses during a simulated territorial challenge. Contrary to expectations, the testosterone treatment did not elicit a stronger aggressive response towards a simulated intruder than in control females. Furthermore, testosterone levels of control females were not elevated during the challenge, and were actually lower after the challenge than before it. Our study did not find any evidence that exogenous testosterone increases aggression in female Barred Buttonquails.
Highlights
In sex-role-reversed species, females typically establish and vigorously defend breeding or feeding territories, and show stronger intra-sexual competition for mates than males (Clutton-Brock and Vincent 1991)
The significant interaction between experimental group and time of measurement (F1, 10.32 = 83.10, p < 0.001) indicates that the testosterone levels of testosterone-implanted females significantly increased after implantation, while testosterone levels of control females after implantation were equal to baseline levels (Table 1)
Control females with unmanipulated hormone levels and females of the experimental testosterone group approached the decoy with similar latencies, and neither of these groups showed any form of highly aggressive behaviour towards the simulated intruder
Summary
In sex-role-reversed species, females typically establish and vigorously defend breeding or feeding territories, and show stronger intra-sexual competition for mates than males (Clutton-Brock and Vincent 1991). The males of these species, on the contrary, take care of the young, often without any help from the females (Clutton-Brock and Vincent 1991). In many bird species, the level of the androgen testosterone is typically higher in males than in females, and during the breeding season male testosterone levels rise, activating and modulating courtship and agonistic behaviour (reviewed by Wingfield et al 2006). Experimentally elevated testosterone levels in males can lead to an increase in territorial aggression (Soma 2006; Wingfield et al 2006), while a simulated territorial intrusion can cause an increase in circulating testosterone levels in males (Wingfield 1985; Wingfield and Wada 1989, but see Goymann 2009)
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