The Effects of Population Density on Survival and Metamorphosis in American Toad ( Bufo americanus ) tadpoles

The American toad ( Bufo americanus ) is an explosive breeder, with females producing hundreds of eggs each season. Here we present an examination of the effects of B. americanus larval density on developmental rate, mass at metamorphosis, and survival under controlled laboratory conditions. In these tests we found that tadpoles reared in high density conditions (sixteen tadpoles/container) took significantly longer to reach metamorphosis than tadpoles reared individually or in densities of four or eight individuals/container. Tadpoles housed in densities of sixteen individuals/container demonstrated significantly higher body mass than tadpoles reared in densities of four or eight individuals. Survival rates increased as tadpole density decreased, with 100% survival for tadpoles reared individually and only 45% survival for tadpoles reared in groups of sixteen. These results show that tadpole density has significant effects on development in B. americanus , with both costs and benefits associated with high and low densities.