Demographic analysis of the Columbia spotted frog (Rana luteiventris): case study in spatiotemporal variation

This study examined size, mass, sex ratios, and age structure of the Columb ia spotted frog (Rana luteiventris) at seven sites in the Toiyabe Range in central Nevada from 1994 through 1996. Age structure was estimated using sk eletochronology. Demographic composition was found to be significantly diff erent among sites, suggesting that localized factors influence recruitment and mortality rates. Demographics among years at the sites were also signif icantly different, indicating that the population dynamics of this system a re complex and are also driven by one or more temporal factors. Knowledge o f local land-use patterns and anecdotal observations were incorporated in a n attempt to identify potential stress agents in need of further research a nd possible intensive management. Differences in recruitment, survivorship, and mortality rates among sites may be due to microclimate, food availabil ity, and predation rates. Introduction of exotic trout and cattle are likel y the most important anthropogenic factors limiting the distribution and pe rsistence of R. luteiventris in the study area. Extreme variations in annua l weather patterns may account for many differences observed at some sites. This study demonstrates that adequate assessment of amphibian population s tatus requires knowledge of subpopulation demographics across a broad lands cape.