Rana sierrae

Vredenburg et al. (2007) examined phylogeography of Rana muscosa as defined by Stebbins (2003) and determined that R. muscosa occurs in the southern Sierra Nevada and in mountains to the south and that populations in the Sierra Nevada north of this range comprise a distinct species (Rana sierrae).

This species is endemic to the Sierra Nevada Mountains of California. The population suffered steep declines of 69-93% due to chytrid fungus and other diseases, invasive trout species, and habitat degradation. Threats from chytrid fungus, invasive trout species, and climate change-induced drought are still ongoing. However, the population decline may have stabilized due to habitat conservation efforts.

This species is endemic to the Sierra Nevada Mountains of California. The historical range extended from the Diamond Mountains northeast of the Sierra Nevada in Plumas County, and from just north of the Feather River in the extreme northwest region of the Sierra Nevada, California, south through the Sierra Nevada to Inyo County, California, and east to Mt. Rose, northeast of Lake Tahoe, in Washoe County, Nevada (Vredenburg et al. 2007). West of the Sierra Nevada crest, the southern part of the range is bordered by ridges that divide the Middle and South Fork of the Kings River, ranging from Mather Pass to the Monarch Divide; east of the Sierra Nevada crest, R. sierrae occurs in the Glass Mountains just south of Mono Lake (Mono County) and along the east slope of the Sierra Nevada south to the type locality at Matlock Lake (Inyo County) (Vredenburg et al. 2007, USFWS 2014). Rana sierrae is now extirpated from Nevada and from large portions of the historical range in the Sierra Nevada of California. Elevational range is 1,370-3,690 meters (Fellers et al. 2013). Using non-extirpated California Natural Diversity Database (CNDDB) (2026) records, range extent is estimated to be 28,677 km² (RARECAT 2025).

Using non-extirpated CNDDB (2026) records, 79 occurrences are estimated (RARECAT 2025).

Decline has been attributed to the effects of the amphibian chytrid fungus, introduced trouts, pesticide exposure, or a combination of factors (Bradford 1989, Knapp and Matthews 2000, Davidson et al. 2002, Davidson and Knapp 2007, Sodhi et al. 2008, Sparling and Fellers 2009, Briggs et al. 2010, Vredenburg et al. 2010, California Department of Fish and Game 2011, Fellers et al. 2013).

Extensive surveys in the Sierra Nevada clearly demonstrate the strong detrimental impact of introduced trouts on R. muscosa/Rana sierrae populations (Bradford 1989, Knapp and Matthews 2000, USFWS 2014, Wilkins et al. 2019). Removal of non-native fishes (relatively easy in some Sierra Nevada lakes) might easily reverse the decline (Knapp and Matthews 2000, Knapp et al. 2016). Some declines have been associated with amphibian chytrid fungus (Vredenburg et al. 2010, USFWS 2014, Wilkins et al. 2019), but at least one population has remained relatively stable despite the presence of the fungus for many years (Fellers et al. 2013). Combined infections of chytrid fungus and ranavirus may be particularly fatal (Smith et al. 2017). See Bradford (1991) for information on mass mortality and extinction of a population due at least in part to red-leg disease and predation on metamorphs by Brewer's blackbird; reestablishment of the extirpated population probably will be prevented through predation by introduced fishes. Frogs of the Rana muscosa/Rana sierrae complex are possibly but probably not threatened by sublethal effects of low pH and elevated levels of dissolved aluminum (Bradford et al. 1992). Climate change is expected to detrimentally affect this species if drought increases (Wilkins et al. 2019).

Davidson et al. (2002) found support for the hypothesis that airborne agrochemicals have played a significant role in the decline of frogs of the Rana muscosa/Rana sierrae complex, but subsequent study of pesticide presence versus yellow-legged frog population trends (Bradford et al. 2011) found no support for the hypothesis that pesticides have contributed to the population declines of R. muscosa and R. sierrae in the alpine zone of the southern Sierra Nevada.