California Red-legged frog (Rana aurora draytonii)
Latest Update...March 20, 2014 Genetic studies indicate that the isolated populations of the very rare red-legged frog in the northern Sierra Nevada are more closely related to red-legged frogs in the Southern California coastal region, than to the San Francisco Bay area populations. Read the new research in Richmond et al (2014), below.
The Red-legged frog has been listed as a threatened species by the U.S. Fish and Wildlife Service since 1996 and is the largest native frog in the western U.S. Red-legged frogs have been eliminated from more than 70 percent of their historic habitat and although their distribution in the Sierra Nevada appears to have not changed significantly from historical records, their populations are small and habitat continues to be eliminated or degraded. Habitat loss is a major cause for the loss of this species from the Sierra Nevada and has come about due to human population and development pressures, dams and diversion, road construction, livestock grazing, timber harvesting, and mining. Other causes that have contributed to population extirpation are the prevalence of pesticides and herbicides in their core habitat and the introduction of non-native bull frogs which prey on the species. This frog was a sought-after gourmet menu item for San Francisco restaurants last century, and over-hunting by early European settlers also contributed to the species decline.
The habitat of Red-legged frogs, labeled as riparian-upland, is identified as habitat within a distance of 200 feet from the edge of the aquatic, riparian, or wetland habitat. This habitat includes structure that provides shade, moisture and cooler temperatures and can include boulders, rocks, woody debris, downed logs, or man made objects. They require these riparian and upland areas for their dense vegetation and open areas for cover, hibernation areas, food sources, and reproduction and spawning grounds. Recent research on California red-legged frog movement suggests that these frogs are primarily aquatic, especially during the breeding season, and typically remain at or very close to the breeding pond. It has been estimated that upwards of 75% of the species historic habitat has been lost, removed, or significantly degraded; however recent research (Barry and Fellers 2013) suggests that the extent of populations in the Sierra Nevada has not changed much, if any, from historical distribution. It is possible that this species was always uncommon or rare in the Sierra Nevada, because of its unique habitat requirements; and although much habitat has been lost due to human-related activities, additional habitat has also been created from 19th century mining talings ponds, in-stream impoundments, and pre-1940 lumber mill ponds (ibid). SInce the CRLF was listed in 1996, ten hitherto unknown populations of the frog have been located in the Sierra Nevada, and authors Barry and Fellers believe that more sites remain to be located.
Due to the fact that the Red-legged frog is highly threatened in the Sierra Nevada, only a significant change to land management practices and a cessation of some of the activities which threaten aquatic habitat in the remaining areas thought to support the species will bring about hope for a future for them in the Sierra Nevada. The Sierra Nevada Framework Plan of 2001 provides strategies to reduce all the factors causing a decline in Red-legged frog populations including prohibition of pesticides from frog habitat, removing livestock near lakes and pond areas, prohibiting development of new recreation trails that would affect known frog sites, and the identification of Critical Aquatic Refuges to protect sensitive species. The 2004 revisions to the Framework have weakened the protections for this species by failing to maintain grazing restrictions for amphibian species in key habitats. A return to a robust monitoring and restoration program as promoted and required by the original Sierra Nevada Framework is vital in the effort to protect the species from disappearing form the Sierra Nevada altogether.
A federally listed threatened species since 1996, the Red-legged frog has had a long struggle to ensure the protection of the habitat that is vital to its survival. In 2001 the U.S. Fish and Wildlife Service (USFWS) designated 4.1 million acres as critical habitat for the species and reaffirmed that decision in 2004 following a string of legal appeals filed on behalf of the Homebuilders Association of Northern California which saw the critical habitat designation reduced to 200,000 acres in 2002 (following a closed-door Consent Decree agreement between the USFWS and developers). In 2006 however, the USFWS reversed its decision once again under pressure from developers and reduced the critical habitat designation to approximately 450,000 acres. In July of 2007, the USFWS announced that it was undertaking a review of decisions made by former Assistant Deputy Secretary Julie MacDonald. Among the many damaging decisions made during her tenure were decisions made regarding the Red-legged frog which favored developers at the expense of imperiled wildlife. While the USFWS has been succumbing to political and special interest pressure and ignoring both the best available science and the letter and intent of the Endangered Species Act, this amphibian has continued to plummet toward complete extirpation from the Sierra Nevada.
Recent research (Richmond et al 2014) found genetic differences that suggest that the northern Sierra Nevada populations of red-legged frogs are more closely related to those in the Souther California coastal region, than to the more abundant populations of the frog in the SF Bay area. In order to facilitate gene flow between the isolated existing populations in the Sierra Nevada, the researchers recommend creation of new breeding ponds and managing existing ponds to support breeding within dispersal distance of occupied habitat (approximately 0.2 – 3.2 km), in order to restore the original, metapopulation-like structure to existing sites.
Barry, Sean J., and Gary M. Fellers. 2013. History and status of the California red-legged frog (Rana draytonii) in the Sierra Nevada, California, USA. Herpetological Conservation and Biology 8: 456-502. (2 MB PDF)
Fellers, G. M. and G. Guscio. 2004. California red-legged frog surveys of Lower Redwood Creek, Golden Gate National Recreation Area. Prepared for National Park Service.
USGS, Western Ecological Research Center, Point Reyes, CA. 62pp. (244KB PDF)
Richmond, J.Q., A.R. Backlin, P.J. Tartarian, B.G. Solvesky, and R.N. Fisher. 2014. Population declines lead to replicate patterns of internal range structure at the tips of the distribution of the California red-legged frog (Rana draytonii). Biological Conservation 172:128-137. (1.78 MB PDF)
Ford, L.D., et al. 2013. Managing Rangelands to Benefit California Red-legged Frogs and California Tiger Salamanders. Livermore, California: Alameda County Resource Conservation District. (5.0 MB PDF)
2002 U.S. Fish and Wildlife Service Recovery Plan (2.37MB PDF)
2002 Consent Decree Decision (162KB PDF)
California Department of Fish and Game Natural History Information --This California state website contains rather limited and old information but is a good basic background composite for the species. Choose from a drop-down list to select the animal you are interested in.