Foothill Yellow Legged Frog

Gray, brown, reddish or olive above; sometimes plain-colored but more often spotted and mottled with dusky hues. Colors usually harmonize with the prevailing color of rocks and soil. Yellow extends from the underside of the hind legs onto the lower abdomen. Snout with a triangular, usually buff-colored patch from its tip to a line connecting the eyelids. Throat and chest often dark-spotted. Skin, including the eardrums, granular. Indistinct dorsolateral folds. Inconspicuous vocal sac on each side of throat, in front of the forelimbs (Stebbins 1985).Male Rana boylii establishing its territory.Run-time: 1:55.Video submitted by Pierre Fidenci. Male and gravid female Rana boylii during mating season.Run-time: 1:24.Videos submitted by Pierre Fidenci. This species was featured as News of the Week on 13 August 2018: Rana boylii, the Foothill Yellow-legged Frog of Oregon and California, is a declining species considered to function as a "sentinel" for assessing ecological health of stream ecosystems. Its phylogeography was studied using a large dataset (RADseq) in a landscape genomics approach (McCartney-Melstad et al. 2018). The five primary clades are extremely differentiated, with about half of the range occupied by a rather genetically uniform population. The peripheral clades are hierarchically substructured and should be treated as separate management units for conservation purposes (rather than previous watershed units). The species is apparently extinct in southern California and the southwestern-most peripheral clade in Monterey County is near extinct and shows the lowest genetic diversity. This study finds Foothill Yellow-legged Frog to be one of the most genetically diverse frog species and points the way for improved species recovery targets (David B. Wake).This species was featured as News of the Week on 25 February 2013: The effects of dams are well documented on fish species (e.g., salmon) but less is known about how dams affect amphibians. A paper in Conservation Biology shows that dams negatively affect river-breeding frogs in California, such as Rana boylii. Kupferberg et al uses 20 years of frog breeding data from regulated (dammed) and unregulated (un-dammed) rivers to show that by altering the flow regime, dams are causing higher egg and tadpole mortality. Dammed rivers that add artificial peak flows in summer months, for example for boating recreation, have the worst impact on native amphibians. (Vance Vredenburg)

Range: West of crest of Cascade Mountains, Oregon, south in coastal mountains of California, to San Gabriel River, Los Angeles Co.; Sierra Nevada foothills to about 1830 m (near McKessick Peak, Plumas Co.); San Pedro Martir (lower end of La Grulla meadow, 2040m), Baja CA. Isolated populations in Elizabeth Lake Canyon and San Gabriel River drainage (near Camp Rincon), Los Angeles Co,; Sutter Buttes, Butte Co., CA (Stebbins 1985). The Camp Rincon population is perhaps now extinct (Lind et. al. 1996). A single record 8 km north of Lodi, San Juaquin Co., CA, perhaps a stray from the Sierran foothills (Lind et. al. 1996). Habitat: Streams and rivers in woodland, chaparral, and forest. (Stebbins 1985) Found: Near water, especially near riffles where there are rocks and sunny banks. When frightened, it dives to the bottom and takes refuge among stones, silt, or vegetation. (Stebbins 1985)

Breeds from the latter part of March to the first of May. Females oviposit eggs in shallow water toward the margin of streams, attached to sides of stones in the stream bed. Eggs are laid in clusters (Wright and Wright 1949). Voice is seldom heard. It is a guttural, grating sound either at one pitch or with rising inflection, a single croak lasting 1/2-3/4 of a second. Four or five croaks may be given in rapid series followed by a rattling sound, with the entire sequence lasting about 2.5 seconds (Stebbins 1985).

Official: A California species of special concern; a candidate for Federal Listing (Lind et. al. 1996). Trends: Notable declines in southern California and the west slope drainages of the Sierra Nevada and southern Cascade Mountains (Lind et. al. 1996). Threats: Construction of dams. Predation by bullfrogs (Rana catesbeiana), a non-native species, occurs (Lind et. al. 1996). Throughout much of the Pacific Coast and Sierra Nevada drainages, the once abundant Foothill Yellow-legged frog (Rana boylii) has been disappearing, mainly due to habitat destruction, water diversion and pollution. In 2005, only 30 California sites had populations of 20 or more adults, including in the heart of their range in California’s north coast where the frogs have lost a quarter of their historic sites. On December 14, 2016, the Center for Biological Diversity (CBD) formally petitioned the US Fish And Wildlife Service to list the Foothill Yellow-legged frog as a threatened species under the California Endangered Species Act. This joins the the CBD’s 2012 petition for federal listing under the Endangered Species Act. Hopefully the state can act to protect this frog faster than the federal officials, who are expected to make a decision in 2020, none too soon for a disappearing species.