Aggression, color signaling, and performance of the male color morphs of a Brazilian lizard (Tropidurus semitaeniatus)

Abstract

Behavior can help to establish dominance in intrasexual interactions, preventing more costly aggressive interactions and improving access to mates. Distinct color morphs often correlate with behavior, driving differential reproductive success between them. The lizard Tropidurus semitaeniatus usually expresses two male color morphs, Yellow or Black. It is likely that morphs play a role in reproduction, which is still unexplored. Here, we test whether there is morph-related dominance during intrasexual interactions. We used ex situ behavioral trials to test whether a particular morph shows dominance, gathering dominance by attributing scores to aggressive/evasive behaviors. We also tested whether winner individuals show higher performance (sprint speed), and whether spectrophotometric measures of body coloration predict winners of male encounters. Morphs showed differences in behaviors suggesting alternative behavioral tactics: Black males behave more aggressively and less evasively while Yellow males show the opposite sets of behavior. Black males also tend to be dominant, but dominants do not show higher sprint speeds than submissive males. Chest coloration, often displayed during encounters, highly predicts winnings (particularly high yellow chroma and low lightness and UV). Our results show that lizards signal competitive condition by behaviorally exposing their chest. Males displaying more head bobs and with darker chests are more likely to win encounters. Our results suggest that Yellow males might undertake a sneaker tactic, preventing aggression costs by evasiveness even though they might perform similarly to Black males. Further studies should address whether female preference is biased in relation to male morphs and its colorations, which would suggest selective processes towards costly signals and morph maintenance.

Significance statement

In the struggle for survival and reproduction, often, there is no single best strategy and multiple distinct tactics may evolve. Behavior, color signaling, and performance are frequently correlated with distinct color morphs, which can coexist as alternative mating tactics. However, studies that are able to integrate all these traits are scarce. Here, we test whether different color morphs of the lizard Tropidurus semitaeniatus show different behaviors and dominance patterns. We also test whether these color morphs differ in their performances (sprint speed) and visual signaling (behavioral displays and intensity of coloration). We demonstrate that Black and Yellow-morph males adopt distinct behavioral tactics: an aggressive (Black-morph) and an evasive (Yellow-morph) tactic. We also show that dominance is highly correlated to chest’s intensity of dark yellow colorations and that lizards signal their dominance status through displays of head bob bouts.