Identifying Shasta County True Frogs

The True Frog family, Ranidae, is a family of frogs that are typically slim wasted, long legged, heavily webbed rear feet, and are excellent jumpers. The family is present on every continent except Antartica.

This does not mean that frogs in other frog families are not really frogs, "True Frog" is just the common family name.

Historically there were four species found within our county borders. A fifth has been introduced and two native species are thought to have been extirpated.

The Oregon Spotted Frog has almost certainly been extirpated. They probably barely came into Shasta County to begin with, are highly sensitive to habitat alteration, and were found in the vicinity of Fall River Mills which has had significant habitat alteration for agriculture.

The California Red-legged Frog also is thought to have been extirpated, though I have hope that remnant populations still persist. The species is in serious trouble throughout most of California, but has a habit of utilizing cattle stock ponds where they sometimes persist for some time unknown to the public or the land owner. Given that a fair amount of cattle ranching takes place in Shasta County, it would not surprise me at all if remnant populations are utilizing them here.

Our various True Frog species can usually be reliably identified by a combination of identification keys, habitat, historic range, and elevation.

All American Bullfrog and Foothill Yellow-legged Frog photos are Shasta County examples. One of the Cascades Frog photos is a Shasta County example. The other Cascades Frog photo is from Siskiyou County. All of the California Red-legged Frog and the Oregon Spotted Frog photos are from outside Shasta County. The photo of the California Red-legged Frog underside is actually of a close relative, the Northern Red-legged Frog.

Use Range Maps

The American Bullfrog and Foothill Yellow-legged Frog probably can be found throughout Shasta County except at higher elevations.

The Cascades Frog is a montane frog that historically in Shasta County was probably restricted to the eastern portion of Shasta County and probably was restricted to elevations above 760 meters (2600 feet), most commonly found well above that elevation. Some populations still persist in Shasta County but most populations have been extirpated and several of the few remaining populations may no longer be viable.

The California Red-legged Frog historically was found primarily in the foothills around the lower Sacramento River Valley, possibly restricted to elevations below 900 meters (about 3,000 feet).

A single Oregon Spotted Frog museum voucher exists from the Pit River drainage in the extreme northern part of the county, in the vicinity of Fall River Mills. To the best of my knowledge, that old museum specimen is the only record of the species in Shasta County. The species is thought to now be extinct in California though remnant populations may still persist in Modoc County. The species is critically endangered in Oregon, Washington, and Brittish Columbia.

Dorsolateral Fold

The dorsolateral fold is a fold of skin that typically extends from the eye to the hind quarters on each side of a true frog. While they are a distinctive feature of true frogs, not all true frogs have dorsolateral folds.

American Bullfrog Foothill Yellow-legged Frog Cascades Frog California Red-legged Frog Oregon Spotted Frog
Lithobates catesbeianus Rana boylii Rana cascadae Rana draytonii Rana pretiosa
Completely lacking Lacking or Weak Distinct Distinct Usually present, often weak
[Dorsolateral of the American Bullfrog] [Dorsolateral of the Foothill Yellow-legged Frog] [Dorsolateral of the Cascades Frog] [Dorsolateral of the California Red-legged Frog] [Dorsolateral of the Oregon Spotted Frog]
Courtesy of CaliforniaHerps.com Courtesy of CaliforniaHerps.com

Ear Fold

The ear fold is a fold of skin that exists on some frog starting at the eye and wrapping around the tympanum (visible part of ear) usually ending near the shoulder.

American Bullfrog Foothill Yellow-legged Frog Cascades Frog California Red-legged Frog Oregon Spotted Frog
Lithobates catesbeianus Rana boylii Rana cascadae Rana draytonii Rana pretiosa
Distinct Weak or Absent Weak or Absent Weak or Absent Weak or Absent
[Ear Fold of the American Bullfrog] [Ear Fold of the Foothill Yellow-legged Frog] [Ear Fold of the Cascades Frog] [Ear Fold of the California Red-legged Frog] [Ear Fold of the Oregon Spotted Frog]
Courtesy of CaliforniaHerps.com

Jaw Stripe

The jaw stripe is a light colored stripe that runs from the nose to near shoulder along the upper jaw on some True Frogs..

American Bullfrog Foothill Yellow-legged Frog Cascades Frog California Red-legged Frog Oregon Spotted Frog
Lithobates catesbeianus Rana boylii Rana cascadae Rana draytonii Rana pretiosa
Lacking Lacking Distinct cream or white, typically runs to top of shoulder Less distinct and not as bright as in the Cascades Frog or the Oregon Spotted Frog. Typically ends before it reaches shoulder. Distinct cream or white, typically runs to top of shoulder
[Jaw Stripe of the American Bullfrog] [Jaw Stripe of the Foothill Yellow-legged Frog] [Jaw Stripe of the Cascades Frog] [Jaw Stripe of the California Red-legged Frog] [Jaw Stripe of the Oregon Spotted Frog]
Courtesy of CaliforniaHerps.com Courtesy of CaliforniaHerps.com Courtesy of CaliforniaHerps.com

Dorsal Color and Pattern

Pattern can be highly variable and in most cases is the probably the least reliable identification key.

American Bullfrog Foothill Yellow-legged Frog Cascades Frog California Red-legged Frog Oregon Spotted Frog
Lithobates catesbeianus Rana boylii Rana cascadae Rana draytonii Rana pretiosa
Typically brown to olive green above, often mottled with irregular darker blotches. Usually a lighter green without mottling on the face in front of the ear fold. Bands on rear legs, more prominent in adults. Specimens with reddish tint have been found in their native range back east, but to my knowledge not in Shasta County. Highly variable, frequently matches the rocks on stream bottom. No distinct spots. Sometimes lacks distinct banding on legs. Specimen below is atypical but demonstrates just how highly variable the pattern can be. Often has a distinct light triangle on head, but many specimens I have found near Redding lack that feature. Brown, tan, or olive green above. Ink black spots on back and sides, usually sharply defined and sometimes with light center. Distinct banding on rear legs. Grey, brown, olive or reddish ground color. Irregular blotches often with some black flecks. Usually has a face mask, distinct banding on hind legs. Snout often more pointed than our other True Frogs. Brown, dull olive green, or reddish above. Ink black spots on back without distinct borders, sometimes with light center. Side generally lacking spots and mottling as it approached venter. Eyes slightly upturned.
[Pattern of the American Bullfrog] [Pattern of the Foothill Yellow-legged Frog] [Pattern of the Cascades Frog] [Pattern of the California Red-legged Frog] [Pattern of the Oregon Spotted Frog]
Courtesy of CaliforniaHerps.com Courtesy of CaliforniaHerps.com Courtesy of CaliforniaHerps.com

Groin and Legs

Very young native True Frogs may not have color on the underside of their legs. However, by the time they are large enough to be confused with a young Bullfrog, they typically do. The color may be less distinct in the Cascades Frog.

Due to the protected status of our native Rana species, they generally should not be handled at all to inspect the groin region. The images here are for informational purposes and are not intended to encourage handling of our native Rana species. Feel free to handle Bullfrogs if you desire.

American Bullfrog Foothill Yellow-legged Frog Cascades Frog California Red-legged Frog Oregon Spotted Frog
Lithobates catesbeianus Rana boylii Rana cascadae Rana draytonii Rana pretiosa
Cream, often mottled with Grey Mottled Yellow Yellow, Orange-Yellow, or Yellowish Tan Mottled Red Red or Salmon, appears painted on
[Groin of the American Bullfrog] [Groin of the Foothill Yellow-legged Frog] [Groin of the Cascades Frog] [Groin of the California Red-legged Frog] [Groin of the Oregon Spotted Frog]
Courtesy of CaliforniaHerps.com

Tadpoles

Please note that the only True Frog tadpole in Shasta County that is legal to collect from the wild or handle without permit is the American Bullfrog tadpole. That makes identification a little more difficult since tadpoles do not make a habit of swimming upside down.

Much of the data here is from Stebbins 2003, which has an excellent section dedicated to amphibian larvae identification starting on page 433.

American Bullfrog Foothill Yellow-legged Frog Cascades Frog California Red-legged Frog Oregon Spotted Frog
Lithobates catesbeianus Rana boylii Rana cascadae Rana draytonii Rana pretiosa
Olive green above with dark speckles. Cream to yellowish below. Maximum size about 16.2 cm (6.5 in.) Olive gray with brown mottling. Maximum size about 5 cm (2 in.) Dark brown above, occasionally greenish. Silverish to brassy below. Maximum size about 5 cm (2 in.) Dark brown or yellowish above, belly has distinctive pink hue. Maximum size about 7.5 cm (3 in.) Uniformly dark above, flecked with gold. Iridescent bronze below. Maximum size 10cm (4 in.) but usually not more than 7.5cm (3 in.)
[Tadpole of the American Bullfrog] [Tadpole of the Foothill Yellow-legged Frog] [Tadpole of the Cascades Frog] [Tadpole of the California Red-legged Frog] [Tadpole of the Oregon Spotted Frog]
 
 
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