Hormone AVT affects competitive behavior in Hyla chrysoscelis

Abstract

Hormones play an important role in animal social behavior, including competitive behaviors. Previous studies demonstrate that the hormone Arginine Vasotocin (AVT) modulates the calling behavior of different frog species. Male frogs produce acoustic advertisement calls to attract females and compete with one another by increasing their call rate and call duration. Previously, AVT has been shown to correlate with increased call rate and call duration; however, how competition influences this relationship remains unknown. We investigated how the effects of AVT would be impacted by different competitive environments in the gray treefrog Hyla chrysoscelis. Frogs were caught and injected with either a saline control (n=14) or AVT (n=23) and then sequentially exposed to noncompetitive, moderately competitive, and highly competitive environments via playbacks of synthetic calls with differing call rates and durations. AVT frogs had higher duty cycles in noncompetitive environments and higher call rates in both competitive and noncompetitive environments. These results indicate that AVT has a competitive advantage in noncompetitive environments, but that this advantage is lost in competitive environments. This has important implications for the overall competitiveness of an individual and the individual's subsequent reproductive success.