Abteilung für Verhaltensneurobiologie, Max-Planck-Institut für Ornithologie, Seewiesen, Germany.
Gen Comp Endocrinol. 2013 Apr 1;184:93-102. doi: 10.1016/j.ygcen.2012.11.027. Epub 2013 Jan 18.
Testosterone has been suggested to be involved in the regulation of male territorial behavior. For example, seasonal peaks in testosterone typically coincide with periods of intense competition between males for territories and mating partners. However, some species also express territorial behavior outside a breeding context when testosterone levels are low and, thus, the degree to which testosterone facilitates territorial behavior in these species is not well understood. We studied territorial behavior and its neuroendocrine correlates in male black redstarts. Black redstarts defend territories in spring during the breeding period, but also in the fall outside a reproductive context when testosterone levels are low. In the present study we assessed if song output and structure remain stable across life-cycle stages. Furthermore, we assessed if brain anatomy may give insight into the role of testosterone in the regulation of territorial behavior in black redstarts. We found that males sang spontaneously at a high rate during the nonbreeding period when testosterone levels were low; however the trill-like components of spontaneously produced song contained less repetitive elements during nonbreeding than during breeding. This higher number of repetitive elements in trills did not, however, correlate with a larger song control nucleus HVC during breeding. However, males expressed more aromatase mRNA in the preoptic area - a brain nucleus important for sexual and aggressive behavior - during breeding than during nonbreeding. In combination with our previous studies on black redstarts our results suggest that territorial behavior in this species only partly depends on sex steroids: spontaneous song output, seasonal variation in trills and non-vocal territorial behavior in response to a simulated territorial intruder seem to be independent of sex steroids. However, context-dependent song during breeding may be facilitated by testosterone - potentially by conversion of testosterone to estradiol in the preoptic area.
睾酮被认为参与了雄性领域行为的调节。例如，睾酮的季节性高峰通常与雄性为争夺领地和交配伙伴而进行的激烈竞争时期相一致。然而，一些物种在繁殖期外也会表现出领地行为，此时睾酮水平较低，因此睾酮在这些物种中促进领地行为的程度尚不清楚。我们研究了雄性黑红鹟的领地行为及其神经内分泌相关性。黑红鹟在繁殖期的春季会保卫领地，但在繁殖期外的秋季，当睾酮水平较低时，它们也会保卫领地。在本研究中，我们评估了歌曲输出和结构是否在整个生命周期阶段保持稳定。此外，我们评估了大脑解剖结构是否能深入了解睾酮在调节黑红鹟领地行为中的作用。我们发现，当睾酮水平较低时，雄性在非繁殖期会以很高的速度自发鸣叫；然而，在非繁殖期自发产生的鸣叫声中，颤音的类似颤音成分所含的重复元素比繁殖期少。然而，在繁殖期，颤音中的重复元素数量与 HVC （song control nucleus，即鸣禽控制鸣唱的核团）体积的增加并没有相关性。然而，雄性在繁殖期比在非繁殖期在视前区表达了更多的芳香化酶 mRNA，视前区是一个对性和攻击行为很重要的脑核。结合我们之前对黑红鹟的研究，我们的结果表明，该物种的领地行为部分依赖于性类固醇：自发的鸣叫声输出、季节性的颤音变化以及对模拟领地入侵者的非发声领地行为似乎与性类固醇无关。然而，繁殖期依赖于环境的鸣叫可能是由睾酮促进的——可能是通过在视前区将睾酮转化为雌二醇。
