ARGININE VASOTOCIN INJECTION INCREASES PROBABILITY OF CALLING IN CRICKET FROGS, BUT CAUSES CALL CHANGES CHARACTERISTIC OF LESS AGGRESSIVE MALES

Male cricket frogs, Acris crepitans communicate to males and females u sing advertisement calls, which are arranged into call groups. Calls a t the middle and end, but not beginning of the call group, are modifie d in response to male-male aggressive interactions. We found in this f ield study of male cricket frogs in natural breeding choruses that the peptide hormone arginine vasotocin (AVT) not only increased the proba bility that males called after injections, but also caused modificatio ns in middle and end calls to produce calls characteristic of less agg ressive males. Moreover, AVT-injected males showed significantly great er increases in call dominant frequency than saline-injected males, ag ain, a characteristic of less aggressive males. Cricket frog calls are used to both repel males and attract females, thus call changes may r elate to male-male and/or male-female interactions. Saline-injected ma les also demonstrated significant changes in several call traits, incl uding changes that occurred in the beginning and middle calls of the c all groups, but not the end calls. AVT appeared to block some call cha nges produced through handling. These data suggest that AVT can influe nce acoustic communication in frogs in several ways, including effects on call characteristics and dominant frequency, as well as potentiall y blocking some handling effects. (C) 1995 Academic Press, Inc.