Breeding phenology of the lowland leopard frog (Rana Yavapaiensis): Implications for conservation and ecology

We monitored breeding phenology and population levels of Rana yavapaiensis by use of repeated egg mass censuses and visual encounter surveys at Agua C aliente Canyon near Tucson, Arizona, from 1994 to 1996. Adult counts fluctu ated erratically within each year of the study but annual means remained si milar. Juvenile counts peaked during the fall recruitment season and fell t o near zero by early spring. Rana yavapaiensis deposited eggs in two distin ct annual episodes, one in spring (March-May) and a much smaller one in fal l (September-October). Larvae from the spring deposition period completed m etamorphosis in early summer. Over the two years of study, 96.6% of egg mas ses successfully produced larvae. Egg masses were deposited during periods of predictable, moderate stream flow but not during seasonal periods when f lash flooding or drought were likely to affect eggs or larvae. Breeding phe nology of Rana yavapaiensis is particularly well suited for life in desert streams with natural flow regimes which include frequent flash flooding and drought at predictable times. The exotic predators of R yavapaiensis are l ess able to cope with fluctuating conditions. Unaltered stream flow regimes that allow natural fluctuations in stream discharge may provide refugia fo r this declining ranid frog from exotic predators by excluding those exotic species that are unable to cope with brief flash flooding and habitat dryi ng.