California Red-legged Frog - Zach Streed

Frogs in Peril - Don't Let Them Croak

California Red-legged Frog

( Rana draytonii )

Species Description and Ecology

The California red-legged frog, the largest native frog in the western United States, is such a legend that it is believed to have inspired stories by Mark Twain himself. Adults generally reach a size between 4 and 6 inches. Chiefly a red to brown color, their rough skin is characterized by small, dark rings on the dorsal side. The underside is usually white with bright red patches. They have prominent ridges along their backs, bulbous black eyes, and legs that appear striped like tiger fur.

California red-legged frogs possess vocal sacs and produce audible calls on land rather than in water. They lay eggs that attach to vegetation at the surface of bodies of water, beginning in November and ending in April. They feed mostly on invertebrates, though smaller frogs and even mice have been observed to compose some of their diet. Larvae most likely feed on pond algae.

Geographic and Population Changes

It is believed that prior to European colonization in the Americas, the California red-legged frog thrived in ecosystems from what is now Marin County, California, to Southern Baja California in Mexico. Today, it is only found in isolated habitats in the Sierra Nevada and northern Transverse ranges.

The current population size is unknown, but it is estimated that the California red-legged frog has been extirpated from roughly 70% of its natural geographic range. 

Listing

The ESA lists the California red-legged frog as Threatened on September 21st, 1983 with a Recovery Priority Number of 6C, meaning it has high threats and a low potential for recovery due to conflicts with urban development. A recovery plan was finally published in 2002. 

Causes of Listing, Threats

The decline of the California red-legged frog cannot be traced back to any single factor, but rather a range of chiefly human activities that lead to habitat degradation and destruction. These activities include urbanization, agriculture, mining, overgrazing, pesticides, water pollution, and introduced predators. Some threats are more pressing than others depending on location.

Recovery Plan Summary

The recovery plan outlines five distinct objectives as criteria that must be met in order to remove the listing for the California red-legged frog. I have summarized these criteria as follows:

1. Eight recovery zones across California are outlined by the ESA. Habitats suitable for the California red-legged frog must be instilled and protected within all of these “core areas.” Human activity must not encroach on them in the future.
2. The populations that still exist must remain stable without human intervention. The frogs must be able to help themselves and reproduce of their own accord. These populations must be monitored without any disturbance for 15 years.
3. The populations must be spread throughout the state in a manner which allows for the establishment of successful metapopulations. The frogs are social creatures that tend to migrate from one habitat to another, and currently lack sufficient corridors that facilitate this movement.
4. There must be a stable population in each core area of the historic range of the species.
5. Additional habitat has been set aside expressly for use by the frogs, and it must be maintained and protected.

What can you do?

Did you know that your own backyard could provide vital habitat space for the California red-legged frog? Watersheds and basins serve as important riparian corridors in California. Housing developments often include some degree of open space or greenbelt that channels stormwater away from developed areas. By using native plants such as Platanus racemosa (California Sycamore) and Quercus agrifolia (Coast Live Oak) in these riparian corridors, you can encourage the growth of smaller native species that form suitable habitats for the frogs. Avoid using heavy pesticides in your garden. 

There are even outreach programs designed to protect the California red-legged frog. The Elkhorn Slough Coastal Training Program offers annual workshops dedicated to the identification and protection of this wonderful and curious native amphibian. Visit www.elkhornsloughctp.org to learn more!

It would be shame to lose a species that provides identity and instills a sense of pride for towns across the state of California. Preserving the frogs means preserving their sweet night time serenade under the stars. 

Other Resources:

US Fish and Wildlife Service: Species Profile

https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=D02D

Frogs in My Area: Maps

https://www.fws.gov/sacramento/es/critical-habitat/CA-Red-Legged-Frog/Current/es_critical-habitat-maps_ca-red-legged-frog.htm

Save the Frogs: Newsletter 

http://www.savethefrogs.com/d/amphibians/rana-draytonii.html

Works Cited

U.S. Fish and Wildlife Service. 2002. Recovery Plan for the California Red-legged Frog (Rana aurora draytonii). U.S. Fish and Wildlife Service, Portland, Oregon. viii + 173 pp.