Socially selected ornaments influence hormone titers of signalers and receivers

Abstract

<p id="d10284844e154">Despite the short-term benefits of dishonesty, animals typically communicate honestly. What prevents weak, low-quality individuals from cheating by signaling that they are strong? The general answer is that signals are costly, and only the best individuals can afford to signal strength. However, there are theoretical and empirical challenges associated with identifying the costs that maintain signal accuracy. Here, we provide a new perspective on honest communication by showing that wasps with dishonest signals are aggressively punished, and this punishment has lasting effects on the physiology of the dishonest signaler and those they interact with. We propose that interactions between behavioral and physiological costs of dishonesty could play an important role in maintaining honest communication over evolutionary time. </p><p class="first" id="d10284844e157">Decades of behavioral endocrinology research have shown that hormones and behavior have a bidirectional relationship; hormones both influence and respond to social behavior. In contrast, hormones are often thought to have a unidirectional relationship with ornaments. Hormones influence ornament development, but little empirical work has tested how ornaments influence hormones throughout life. Here, we experimentally alter a visual signal of fighting ability in <i>Polistes dominulus</i> paper wasps and measure the behavioral and hormonal consequences of signal alteration in signalers and receivers. We find wasps that signal inaccurately high fighting ability receive more aggression than controls and receiving aggression reduces juvenile hormone (JH) titers. As a result, immediately after contests, inaccurate signalers have lower JH titers than controls. Ornaments also directly influence rival JH titers. Three hours after contests, wasps who interacted with rivals signaling high fighting ability have higher JH titers than wasps who interacted with rivals signaling low fighting ability. Therefore, ornaments influence hormone titers of both signalers and receivers. We demonstrate that relationships between hormones and ornaments are flexible and bidirectional rather than static and unidirectional. Dynamic relationships among ornaments, behavior, and physiology may be an important, but overlooked factor in the evolution of honest communication. </p>