California Red-legged Frog Monitoring
The California red-legged frog (Rana aurora draytonii) is the largest native frog in the western United States. It was federally listed as threatened in 1996, partly because it has disappeared from 70 percent of its former range. This frog is now is found primarily in coastal drainages of central California. Potential threats to the frog include elimination or degradation of habitat from land development, and habitat invasion by non-native aquatic species. Pesticide drift from the agricultural use of pesticides may also be contributing to the decline in the Sierra foothills.
The USGS field station at Point Reyes has several ongoing research projects that focus on this frog. Since 1993, every pond and several streams at Point Reyes have been surveyed for red-legged frogs. In the breeding season (winter), the location and number of egg masses are recorded. Throughout the year, individual frogs are radio tagged and tracked to determine non-breeding behavior, habitat use at breeding sites, and to monitor dispersal habits in the Olema Valley. Frogs are also tagged with small electronic microchips that are placed under the skin. These tags work like a barcode allowing researchers to identify and record specific data about an individual frog. Selected sites have been surveyed more closely in order to document population trends. Currently there are more than 50 known breeding sites at Point Reyes. Information on the ecology, distribution, and population status of red-legged frogs is being used to develop more effective management strategies.