The neuropeptide arginine vasotocin alters male call characteristics involved in social interactions in the grey treefrog, Hyla versicolor

We investigated the effects of different doses (0, 2.5, 25 and 250 mu g) of the neuropeptide arginine vasotocin (AVT) on the calling characteristics o f the grey treefrog in a chorus in its natural habitat. AVT changed some ca ll characteristics known to influence social behaviour in grey treefrogs. I t increased call duration and number of pulses in a call, but not dominant frequency, call rate or pulse effort. Saline injections and handling did no t produce significant changes in any of the call characteristics. In additi on, individual animals injected with AVT only rarely produced call characte ristics that were outside of the range found in the preinjection measuremen ts, suggesting that AVT does not cause abnormal calling behaviour. Other re searchers have demonstrated that longer calls with more pulses are produced by males when chorus densities increase, and females display a strong pref erence for longer calls with more pulses. This suggests that the changes in duced by AVT injections may have functional consequences in social interact ions. We previously demonstrated that AVT-injected males (25 pg AVT) displa ced resident males from calling sites through changes in calling behaviour under natural field conditions. Our results indicate that changes in call d uration and pulse number could contribute to the unmanipulated resident mal e's behaviour towards the AVT-injected intruder, perhaps because the calls are more attractive to females or because the calls are perceived as more a ggressive. (C) 2000 The Association for the Study of Animal Behaviour.