Meeting Abstract
Collared lizards, Crotaphytus collaris, are sexually dimorphic lizards in which males use their sexually selected traits to defend territories against rivals and to attract females. While not novel, collared lizards are different from other animals in that they present a sexually dimorphic trait as hatchlings that is replaced by adult dimorphic traits once the lizards reach sexual maturity. Hatchlings male lizards develop orange dorsolateral bars that are lost as the lizards become sexually mature. Juvenile males are aggressive toward other juvenile males and use these orange bars in this context. We tested how these orange bars are affecting male-male interactions by conducting behavioral trials that separated the effect of the bars from aggressive behavior. Lizards either had their bars removed (masked with paint) or enhanced (increased area with spectrally similar paint) and received either a hormone implant that increased dihydrotestosterone levels and aggressive behavior, or a blank implant. Treatment lizards were placed in a neutral arena with an unaltered and size-matched stimulus male and behaviors of both lizards were scored to measure relative aggression. Trials showed that the bars and aggressive behavior are linked and that increasing one, either the bars or the aggression, will oppositely alter the outcome of male-male interactions. While lizards with increased aggression via hormone implants were significantly more aggressive in comparison to blank implanted lizards and non-implanted stimulus lizards, lizards with only enhanced orange bars were met with an increase in aggression. When the orange bars were enhanced without the associated level of aggression expected, rival males retaliated against the “cheater” male. This means that lizards police those that act outside of the bounds of their signal.
