The frog mentioned in Mark Twain's famed The Celebrated Jumping Frog of Calavaras County is none other than the California red-legged frog.  This large species, averaging 4.5 inches, was once abundant throughout California's Central Valley.  Adults are nocturnal while the juveniles can be active day or night.

Ellicott Slough National Wildlife Refuge falls into one of the recovery units for this species and Ellicott Unit and Harkins Slough Unit have been identified as critical habitat for its survival.  However, use by the California red-legged frog has not yet been thoroughly assessed at the refuge.