R. draytonii is a moderate to large (4.4–14 cm or 1.7–5.5 in) frog. It is the biggest native frog species in the western United States.[10] The back is a brown, grey, olive, or reddish color, with black flecks and dark, irregular, light-centered blotches, and is coarsely granular. A dark mask with a whitish border occurs above the upper jaw, and black and red or yellow mottling is in the groin. The lower abdomen and the undersides of its hind legs are normally red. The male can be recognized by its large fore limbs, thumbs, and webbing. Only a portion of the toes are webbed, and it uses vocal sacs to grunt during breeding season.[10] The juvenile frog has more pronounced dorsal spotting, and may have yellow, instead of red, markings on the undersides of the hind legs. A characteristic feature of the red-legged frog is its dorsolateral fold, visible on both sides of the frog, extending roughly from the eye to the hip. R. draytonii looks very similar to the northern red-legged frog.
Ecology and behavior
This species has disappeared from an estimated 70% of its range, and is now only found in about 256 streams or drainages in 28 counties of California.[11] However, the species is still common along the coast, and most of their population declines are in the Sierra Nevada and Southern California. The California red-legged frog is an important food source for the endangered San Francisco garter snake in San Mateo County. The California newt is often found with this species due to sharing habitat requirements and the newts eating their eggs.[12] The California red-legged frog primarily eats earthworms, beetles, flies, and other winged insects. There have been instances where the species was viewed preying on juvenile snakes, small mammals such as mice, and other frogs and tadpoles.[13]
Breeding occurs from late December to early April.[10] The male frog's advertisement call is a series of a few small grunts, usually given while swimming around under water. Choruses are weak and easily missed. The adult California red-legged frog is nocturnal, while juvenile frogs are both nocturnal and active during the daytime.[10] The species inhabits dense, shrubby, or emergent riparian vegetation and still or slow-moving perennial and ephemeral water bodies that also serve as breeding sites. This species has been noted to utilize upland habitats as adults near aquatic areas (such as creeks). They often use these zones for basking and searching for prey.[14] They prefer tall plants such as cattails for protection and to lay eggs.[10]
The tadpoles (larvae) of this species may metamorphose into frogs within about 7 months of hatching from the egg, or may overwinter, taking up to 13 months.[15] This is a recent discovery, which may have management implications for the species, particularly when aquatic habitat undergoes modification.
The California red-legged frog exhibits several behaviors when approached by predators. They either stay immobile, quickly leap into vegetation in an upland habitat or a water source nearby, or, rarely, give off an alarm call to indicate danger. They have also been seen demonstrating the unken reflex when caught.[16]
Conservation
California red-legged frog in habitatEgg mass
This frog is listed as threatened and is protected by federal[5][6] and California law. One cause of the population decline is habitat loss and destruction, but introduced predatory species, such as American bullfrogs, might also be a factor. Their habitats are in close proximity to roads and trails, indicating traffic, runoff, pollution, and other human interference may be a significant threat to the species. The species has also been found thriving in undisturbed and isolated ponds in comparison. Vegetation diversity and surface coverage on smaller ponds indicate a greater likelihood of the species being present.[12]
On September 17, 2008, the US Fish and Wildlife Service proposed to more than triple the habitat of the California red-legged frog, citing political manipulation by former Deputy Assistant Secretary Julie MacDonald at the United States Department of the Interior. According to the Los Angeles Times, "development and destruction of wetlands have eliminated the frogs from more than 70% of their historic range. MacDonald would have reduced what was left of the frog's range by 82%."[17] San Mateo County and Monterey County seem to have some of the largest healthy populations of these frogs, especially in coastal wetlands.[18][19]
2010
In March 2010, the US Fish and Wildlife Service announced 1,600,000 acres (6,500 km2) of protected land for the species throughout California, which has implications regarding development and use of such land.[1][20][21] The largest population of the frog will be given protection on a 48-acre stretch of land (19 ha) in Placer County.[22]
2015
A new law designates the California red-legged frog the “state amphibian.” Presently, it is subject to protection under both federal and state laws passed in 1996. Although the designation as official state amphibian does not provide legal protection to the frog as a threatened species, it does highlight the importance that California places on the frog's preservation.[23]
^Frost, Darrel R. (2018). "Rana draytonii Baird and Girard, 1852". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 31 December 2018.
^Bishop, Meghan R.; Drewes, Robert C.; Vredenburg, Vance T. (2014). "Food Web Linkages Demonstrate Importance of Terrestrial Prey for the Threatened California Red-Legged Frog". Journal of Herpetology. 48 (1): 137–143. doi:10.1670/12-288. ISSN0022-1511. S2CID86398970.
^Alvarez, Jeff A.; Wilcox, Jeffery T. (2021). "Observations of Nocturnal Upland Habitat Use by the Rana Draytonii (California Red-Legged Frog), and Implications for Restoration and Other Activities". Ecological Restoration. 39 (3): 155–157. doi:10.3368/er.39.3.155. ISSN1543-4060. S2CID236970675.
^Fellers GM, Launer AE, Rathbun G, Bobzien S, Alvarez J, Sterner D, Seymour RB, Westphal M (2001). "Overwintering tadpoles in the California red-legged frog (Rana aurora draytonii)". Herpetological Review. 32: 156–157. S2CID81756914.
^"California Red-Legged Frog"(PDF). California Department of Pesticide Regulation. 2002. Archived from the original(PDF) on May 25, 2017. Retrieved August 29, 2011.
