Links between color conspicuousness, territorial behavior, and steroids in a color polymorphic lizard

Abstract Discrete color polymorphisms often correlate with other traits, forming suites of characteristics that may be signaled and inform mate-choice decisions and/or dominance interactions with conspecifics. Unraveling the adaptive function and maintenance of stable color polymorphisms thus requires understanding these links and the context in which color traits are used. Here, we conducted a field experiment with robotic models to study the relationship between color morph, territorial behavior and circulating hormones, namely testosterone and corticosterone, in a male-male competition framework using the color polymorphic lizard Sceloporus consobrinus. We found that yellow and orange male color morphs are conspicuous and can be reliably distinguished by conspecifics, making color differences suitable for morph-specific signaling. Orange males exhibited higher baseline rates of push-up displays and bouts of movement compared to yellow males. Lizards of both morphs strongly increased aggressive display behavior in response to intruder robotic models of either the same or different color morph. However, color morphs did not differ in body size (SVL), body condition, or plasma hormonal content (testosterone and corticosterone), suggesting that color could convey information regarding alternative territorial behavior but does not signal differences in individual male “quality” or physiological hormonal state. Color may thus not be sufficient, or the most informative signal in the context of agonistic male contests. Aggressive motion displays may be more effective as a signal of a morph’s resource holding potential than static color. The lack of convergence in correlated phenotypes across similarly polymorphic taxa further suggests that patterns of trait integration are rather species-specific.