Effects of hydroperiod on metamorphosis in Rana sphenocephala

Hydroperiod, the time a temporary pond holds water, is an important factor influencing recruitment in amphibian populations and structuring amphibian communities. We conducted an experiment to test the effect of hydroperiod on metamorphic traits of the southern leopard frog ( Rana sphenocephala ), a common amphibian in the southeastern United States. We reared larval R. sphenocephala in artificial ponds at a density of 32 larvae per tank (initial volume = approximately 650 liter). We dried the tanks according to natural patterns, using three different hydroperiods (60, 75 and 90 d). Experimental hydroperiods had a significant effect on the number of metamorphs and the length of the larval period, but not on overall survival (larvae + metamorphs) nor size at metamorphosis. Our findings confirm a pattern observed in field studies and are similar to results of experimental investigations of closely related ranid frogs. Our results demonstrate that relatively small differences in hydroperiod length ( i.e. , as little as 15 d) may have large effects on juvenile recruitment in R. sphenocephala.