Monitoring and modeling the viability of the Columbia spotted frog (Rana luteiventris)

The Toiyabe Range population of the Columbia spotted frogs is geographically distributed in two watersheds in central Nevada, USA. We used visual encounter surveys (VES) and capture-recapture methods to test the efficacy of a monitoring program. We used a Cormack-Jolly-Seber model to estimate annual survivorship. VES were good predictors of the abundance of frogs at a location. However, VES were not consistent across crews or techniques. Across sites, male and female frogs had similar survivorship. Smaller frogs survived at lower rates than larger frogs. However, survivorship was much higher over 1996--1997 than 1997--1998. Survivorship varied less for larger frogs than smaller frogs. We calculated an annual growth rate of the population of 1.19. For monitoring of population abundance, we recommend capture-recapture sampling. We caution against making long-term predictions from our model due to the large fluctuations in the population during this study.