USING DYNAMIC OCCUPANCY AND STATE SPACE MODELS TO IDENTIFY TRENDS IN A POPULATION OF CALIFORNIA RED-LEGGED FROG (RANA DRAYTONII).
Matthew J. Sharp Chaney; Midpeninsula Regional Open Space District; 330 Distel Circle, Los Altos, CA, 94022; (650) 625-6573; mchaney@openspace.org; Brian J. Halstead
Conservationists working to recover California red-legged frog (CRLF) require methods for assessing trends in CRLF populations over time. This study uses a dynamic occupancy model to determine the number of ponds occupied by CRLF at a preserve in La Honda California over a ten-year period. In addition, the population of breeding female CRLF in each individual pond, and a site-wide analysis combining 13 ponds, was estimated through time using a state space model. Precipitation amounts and the maximum depth of each of the thirteen ponds on site were compared with egg mass detections. Results indicated that CRLFs occupied an average of 25% more ponds per year than surveys suggested. The population trend indicates that the number of breeding female CRLFs is generally stable after recovering from a drought that occurred from 2010 to 2015. Egg mass detections had a moderate positive correlation with rainfall, and no correlation with maximum possible pond depth. The results from the dynamic occupancy model, and state space model, are valuable for assessing population trends if the number of CRLF does not approach zero in a given year. These methods can contribute to CRLF recovery by providing statistically robust estimates of population trends over time.
Ecology and Conservation of Amphibians and Reptiles II