Correlates of vocal display in a Costa Rican population of Strawberry Poison-Dart Frogs, Dendrobates pumilio

Variation in the frequency and intensity of territorial displays occurs within individuals and populations. Such variation should be correlated with variation in potential costs and benefits of the behaviors. We examined temporal variation in vocal displays of male Strawberry Poison-Dart Frogs (Dendrobates pumilio) and investigated correlations with environmental and social factors. Forty-three adult male D. pumilio were studied for six-day sessions. Five vocalization characteristics (total time calling, mean call group duration, number of call groups, call note rate, and proportion of days calling) were quantified. Each of these calling variables was greater between 0630 and 0830 h than at other times through the day. Perch use (occupation of elevated display sites) was greater between 0530 and 0930 h than at other times of day, a period that extends one hour before and after the peak in calling activity. There was no difference between vocalization patterns on or off perches for any of the calling characteristics, but males called during a larger proportion of observations when on perches than when off perches. Snout-vent length was not correlated with any of the calling characteristics. Rainfall during the previous 24-h period was positively correlated with all calling characteristics and perch use.