Department of Animal Behaviour, Bielefeld University, Konsequenz 45, 33615 Bielefeld, Germany; Evolutionary Biology, Bielefeld University, Konsequenz 45, 33615 Bielefeld, Germany.
Department of Animal Behaviour, Bielefeld University, Konsequenz 45, 33615 Bielefeld, Germany; Evolutionary Biology, Bielefeld University, Konsequenz 45, 33615 Bielefeld, Germany.
Horm Behav. 2022 Nov;146:105243. doi: 10.1016/j.yhbeh.2022.105243. Epub 2022 Aug 20.
Success in sperm competition is an important determinant of male fitness in mating systems with female multiple mating. Thus, sperm competition risk represents a key dimension of the male social environment to which individual males are expected to adaptively adjust their reproductive phenotype. Such adaptive phenotypic adjustment we here refer to as male social niche conformance. In this pre-registered study, we investigated how male zebra finches, Taeniopygia guttata, adjust their behavior to sperm competition risk. We experimentally manipulated the opportunity for extra-pair mating to create two levels of sperm competition risk: 1) Single-pair, no sperm competition risk; 2) Double-pair, sperm competition risk. We compared male courtship, mate guarding, copulation rates, and aggression between the treatment groups. To identify hormonal correlates of male behavioral adjustment, we measured plasma testosterone and corticosterone levels before and after the social treatment started. Contrary to our pre-registered predictions, males from the Double-pair treatment group decreased courtship rates compared to those from the Single-pair group, and Double-pair males responded less aggressively towards intruders than Single-pair males. Testosterone levels decreased over the breeding cycle, but social treatment had no effect on either testosterone or corticosterone levels. Our results indicate that male zebra finches do not intensify courtship or competitive reproductive behaviors, or upregulate key hormones when another breeding pair is present. Although we found no evidence for the predicted adaptive behavioral responses to sperm competition risk, we show that male zebra finches plastically adjust their behavior to their social environment.
在有雌性多次交配的交配系统中，成功的精子竞争是雄性适合度的一个重要决定因素。因此，精子竞争风险代表了个体雄性适应调整其生殖表型的关键的雄性社会环境维度。我们在这里提到的这种适应性表型调整，称为雄性社会生态位顺应。在这项预先注册的研究中，我们调查了斑胸草雀雄性如何调整其行为以适应精子竞争风险。我们通过实验操纵额外交配的机会，人为地创造了两个精子竞争风险水平：1）单配对，无精子竞争风险；2）双配对，有精子竞争风险。我们比较了处理组之间雄性的求偶、配偶守护、交配率和攻击性。为了确定雄性行为调整的激素相关性，我们在社会处理开始前后测量了血浆睾丸酮和皮质酮水平。与我们预先注册的预测相反，来自双配对处理组的雄性与来自单配对组的雄性相比，求偶率降低，而双配对雄性对入侵者的攻击性比单配对雄性的反应要小。睾丸酮水平在繁殖周期中下降，但社会处理对睾丸酮或皮质酮水平均没有影响。我们的结果表明，雄性斑胸草雀在存在另一对繁殖伴侣时，不会加剧求偶或竞争繁殖行为，也不会上调关键激素。尽管我们没有发现对精子竞争风险的预测适应性行为反应的证据，但我们表明雄性斑胸草雀可以灵活地调整其行为以适应其社会环境。
