Meeting Abstract
Sexual selection is a powerful means to explain sexually dimorphic traits in animals. Often, the exaggerated dimorphic trait helps the bearer win male-male aggressive interactions. The collared lizard, Crotaphytus collaris, is no exception. These are sexually dimorphic lizards in multiple adult traits; color and body size are two. Even as juveniles, though, lizards are sexually dichromatic since males bear prominent lateral orange bars through their first season. Adults use their dimorphic traits to guard mates and defend territories from rival males to increase fitness. Juvenile males mimic the behavior of adults by being aggressive toward other juvenile males and they use these orange bars in this aggressive context. The orange bars allow for sexual discrimination in juvenile males and may also play a role in signaling aggressiveness of the bearer. Behavioral trials isolating the effect of orange bars from aggressive behavior show the bars and aggressive behavior are linked and that missing one, either the bars (the signal) or the aggression (the behavior), will decrease a lizard’s effectiveness during male-male interactions. While lizards with increased aggression via hormone implants were significantly more aggressive in comparison to non-implanted stimulus lizards, lizards with only enhanced orange bars saw the opposite effect. When the orange bars are enhanced without the associated behavior appropriate for a strong signal, rival males retaliated against the “cheater” male. This means signal honesty would likely be socially enforced and that variation in the orange bar signal could affect fitness of juveniles by sorting which lizards are relegated to less suitable habitats and which remain in better ones.
