NATURAL HISTORY

FOOTHILL YELLOW-LEGGED FROG } Rana boylii
FAMILY: Ranidae

DESCRIPTION: Foothill yellow-legged frogs are small ranid frogs approximately 1.5 to 3 inches long, with females growing to larger sizes than males. Adult frogs can be grey, brown or reddish on their backs, with a distinctive lemon-yellow covering the undersides of their legs.

HABITAT: This frog lives in partially shaded, perennial streams and rivers with rocky substrate at low to moderate elevations, with a range of vegetation types; it is often found in or near riffles and on open, sunny stream banks.

RANGE: The frog ranges from Oregon's Willamette River system south to the Upper San Gabriel River in Los Angeles County, California; it also occupies the western slopes of the Sierra Nevada.

MIGRATION: The species is not migratory, but adults may move modest distances along stream corridors.

BREEDING: Adult frogs congregate on sandy or rocky bars in the spring to mate. Eggs are deposited in shallow, slow-moving water with a cobble or pebble substrate, with egg masses anchored to gravel or vegetation.

LIFE CYCLE: Tadpoles hatch within five to 30 days, then burrow down into the gravel of streams. Tadpoles metamorphose three to four months after hatching. Foothill yellow-legged frogs usually reach sexual maturity after one or two years.

FEEDING: Tadpoles feed on algae. Adults eat terrestrial and aquatic invertebrates, such as flies, moths, mosquitoes, hornets, ants, beetles, grasshoppers, water striders and snails.

THREATS: This species is threatened by dams, water development, water diversions, timber harvest, mining, livestock grazing, roads and urbanization, marijuana cultivation, off-road vehicles, climate change, pollution, invasive species, and disease.

POPULATION TREND: This frog's population has declined more than 50 percent rangewide; it is extirpated from Santa Barbara County south to San Diego County.

 

Foothills yellow-legged frog photo courtesy Flickr/Bree McGhee