The peptide hormone arginine vasotocin (AVT) and its mammalian homolog arginine 
vasopressin modulate a variety of social behaviors in vertebrates. In anurans, 
AVT influences the production of advertisement calls, the acoustic signals that 
males use to attract females and repel rival males. In this study, we 
investigate the effects of AVT on call characteristics in the túngara frog 
(Physalaemus pustulosus). Túngara frogs produce a "whine" that is important for 
species recognition; they may also produce a second, attractive call component, 
the "chuck". We used a field playback experiment to determine changes in male 
calling behavior following treatment with AVT. A previous study showed that AVT 
alters call rate and the production of chucks; in the current analysis, we focus 
on changes in the whine. Males produce shorter whines with higher initial 
frequencies following treatment with AVT. Call changes do not vary with a social 
stimulus. We also used female phonotaxis experiments to investigate the effects 
of call changes on female mate choice. Females disfavor the calls produced by 
males treated with exogenous AVT. We suggest that AVT influences motivation to 
call and the motor control of call production, but that over-stimulation of the 
vocal system limited the production of attractive calls in this experimental 
context.