Recent concern about apparent declines in amphibian populations in many parts of the world (Blaustein et al., 1994; Carey and Bryant, 1995) suggests that there is an urgent need for information about how amphibians are impacted by pollutants. Amphibians have thus become widely used as environmental monitors of effects of water-borne pollutants, and have been found to be lethally impacted by petroleum products (Mahaney, 1994), acidification (Rowe et al., 1992; Sadinski and Dunson, 1992), insecticides (Berrill et al., 1993, 1994), and various metals (Freda, 1991). However, anuran populations may also be impacted sublethally by heavy metals or organic compounds that accumulate in their tissues (Hall and Mulhern, 1984), and that sometimes result in morphological or physiological changes (Tyler, 1989; Alvarez et al., 1994; Rowe et al., 1996, 1998). Substantial morphological or physiological changes resulting from exposure to pollution may require compensatory behavioral changes that modify an individual's interactions with its environment, and thus have potential population-and community-level im-pacts (Little, 1990). Behavioral changes may modify an individual's ability to harvest resources, obtain mates,