Population declines, beginning by the early 1970s, have been observed in Bufo boreas throughout the Southern Rocky Mountains (Corn et al., 1989; Carey, 1993; Corn, 2000). As a consequence, Bufo boreas was listed as an endangered amphibian in Colorado in 1993 (Livo and Loeffler, 2003). Recently, a pathogenic chytrid fungus, Batrachochytrium dendrobatidis (referred to here as BD), has been associated with Bufo boreas population declines at monitored sites in Colorado (Milius, 1999; Livo, 2000; Jones, 2000; Muths et al., 2003). This pathogen has been found to infect a growing number of amphibian species and has been found nearly worldwide, often associated with amphibian population declines (Berger et al., 1998; Speare and Berger, 2000; [...]