Does the Presence of Fish Affect the Distribution of Tree Frogs (Hyla arborea)

In recent years there has been increasing concern over a possible global decline of amphibian populations (Blaustein & Wake 1990). The causes behind a decline are not clear, but factors such as stochastic environmental disturbance, destruction of natural habitat, acid rain, pesticides, and introduction of exotic predators have been invoked (Blaustein & Wake 1990). Most amphibian species have complex life cycles with a terrestrial adult stage and an aquatic larval stage, and the population size of adults may depend on the size and abundance of metamorphs (Wilbur 1980; Smith 1983). Thus, understanding factors that affect the success of the aquatic stage may prove helpful for understanding the current decline in amphibian populations. A number of laboratory and field studies have demonstrated density-dependent growth rates of tadpoles (see Wilbur 1976; Semlitsch & Caldwell 1982; Travis 1983), resulting in differences in larval period and size at metamorphosis, which are correlated with fitnessrelated traits of adult amphibians (see Berven & Gill