Green P A, George E M, Rosvall K A, Johnsen S, Nowicki S
Department of Biology, Duke University, Durham, NC 27708, USA.
Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, TR10 9FE, UK.
Ethology. 2022 Feb;128(2):131-142. doi: 10.1111/eth.13247. Epub 2021 Nov 2.
Many animals use assessment signals to resolve contests over limited resources while minimizing the costs of those contests. The carotenoid-based orange to red bills of male zebra finches () are thought to function as assessment signals in male-male contests, but behavioral analyses relating contest behaviors and outcomes to bill coloration have yielded mixed results. We examined the relationship between bill color and contests while incorporating measurements of color perception and testosterone (T) production, for an integrative view of aggressive signal behavior, production, and perception. We assayed the T production capabilities of 12 males in response to a gonadotropin-releasing hormone (GnRH) challenge. We then quantified the initiation, escalation, and outcome of over 400 contests in the group, and measured bill color using calibrated photography. Finally, because signal perception can influence signal function, we tested how males perceive variation in bill coloration, asking if males exhibit categorical perception of bill color, as has been shown recently in female zebra finches. The data suggest that males with greater T production capabilities than their rivals were more likely to initiate contests against those rivals, while males with redder bills than their rivals were more likely to win contests. Males exhibited categorical color perception, but individual variation in the effect of categorical perception on color discrimination abilities did not predict any aspects of contest behavior or outcomes. Our results are consistent with the hypotheses that T plays a role in zebra finch contests and that bill coloration functions as an aggressive signal. We suggest future approaches, based on animal contest theory, for how links among signals, perception, and assessment can be tested.
许多动物利用评估信号来解决对有限资源的争夺，同时将这些争夺的成本降至最低。雄性斑胸草雀基于类胡萝卜素的橙色至红色鸟喙被认为在雄性间的争夺中起到评估信号的作用，但将争夺行为和结果与鸟喙颜色联系起来的行为分析得出了不一致的结果。我们在纳入颜色感知和睾酮（T）分泌测量的同时，研究了鸟喙颜色与争夺之间的关系，以综合了解攻击信号的行为、分泌和感知。我们检测了12只雄性斑胸草雀在促性腺激素释放激素（GnRH）刺激下的T分泌能力。然后我们对该群体中400多次争夺的发起、升级和结果进行了量化，并使用校准摄影测量鸟喙颜色。最后，由于信号感知会影响信号功能，我们测试了雄性如何感知鸟喙颜色的变化，询问雄性是否像最近在雌性斑胸草雀中所显示的那样，对鸟喙颜色表现出分类感知。数据表明，T分泌能力比对手更强的雄性更有可能向那些对手发起争夺，而鸟喙比对手更红的雄性更有可能赢得争夺。雄性表现出分类颜色感知，但分类感知对颜色辨别能力影响的个体差异并不能预测争夺行为或结果的任何方面。我们的结果与T在斑胸草雀争夺中起作用以及鸟喙颜色作为攻击信号发挥作用的假设一致。我们基于动物争夺理论提出了未来的方法，用于测试信号、感知和评估之间的联系。
