Habitat, spatial population structure, and methods for monitoring barking frogs (Eleutherodactylus augusti) in southern Arizona

Debate over global declines of amphibian populations has focused researchers' attention on the lack of basic life-history information about and appropriate monitoring methods for amphibian species. We studied barking frogs ( Eleutherodactylus augusti) in a canyon in the Huachuca Mountains of southern Arizona. Annual (capture) surveys and radio-tracking revealed that most barking frogs in this canyon are strongly associated with limestone. Adults rarely moved between limestone outcrops and numbers of frogs on each outcrop were small. Subpopulations consisting of frogs on sets of neighboring outcrops probably function as a metapopulation. We evaluated four methods for monitoring population size of this species: mark-recapture, distance sampling, visual encounter surveys, and call counts. We found none of these to be able to detect changes in population size powerfully enough to alert managers to declines as they occur. We suggest resource managers focus monitoring efforts on distribution rather than population size