Amphibians are vulnerable to an array of
environmental changes because of their
permeable skin, a complex life history, and a dependence on moist terrestrial or wetland habitats. These attributes make them excellent indicators of the health of aquatic ecosystems. Amphibians can indicate problems of air and water pollution, drought, habitat loss and
fragmentation, the introduction of non-native species such as sport fish and bullfrogs, and the emergence and spread of infectious disease. Amphibian occupancy is determined using auditory and visual encounters surveys.