Habitat of lowland leopard frogs in mountain canyons of southeastern Arizona
Authors: J. Eric Wallace, Robert J. Steidl, Don E. Swann
Year: 2008 (xl)
Abstract
Freshwater ecosystems and the organisms that inhabit them are imperiled worldwide, especially in the arid southwestern U.S. where aquatic environments are limited and vulnerable to human disturbances. Two of the most imperiled vertebrate taxa in Arizona, fish and amphibians, have declined over much of their ranges and often remain only in relatively undisturbed, isolated, low-order streams. We assessed habitat characteristics associated with presence of lowland leopard frogs, Rana yavapaiensis, in mountain canyons of southeastern Arizona at landscape (canyon) and patch (pool) scales. We surveyed 25 canyons for presence of frogs and measured characteristics of 91 pools within 9 occupied canyons. Canyons that were inhabited by frogs versus those that were uninhabited had larger watersheds (14.3 ± 1.85 km2 versus 6.4 ± 1.60 km2, mean ± SE), wider stream channels (3.4 ± 0.36 m versus 2.0 ± 0.33 m), were closer to the nearest valley stream (2.0 ± 0.77 km versus 5.1 ± 0.67) and had larger perennial pools (61.6 ± 6.87 m3 versus 23.1 ± 5.54 m3). Plunge pools that were inhabited had an average of 13% more perimeter vegetation, 10% more canopy cover and 1.7 more refugia than uninhabited plunge pools. In tinajas, no measured characteristics reliably distinguished inhabited from uninhabited pools. Unless natural hydrological and watershed processes that ensure perennial surface waters in mountain canyons are maintained through appropriate management, populations of leopard frogs and other aquatic organisms inhabiting aquatic refugia in these arid mountain streams will continue to decline.