Foothill Yellow-legged Frog
Rana boylii
![[Foothill Yellow-legged Frog]](/images/20ds.jpg)
Description
Physical
Our smallest true frog, adults reach a size just under 7.5cm (3in) snout to vent. Dorsolateral fold either extremely weak or completely lacking. Somewhat rough granular skin. Like all True Frogs, Foothill Yellow-legged Frog are slim wasted with legs extremely well suited for jumping and have heavily webbed hind feet.
Color and Pattern
Highly variable, usually matches the rocks on the stream bottom. Lacks a face mask or jaw stripe, often has a light triangle on head from the two eyes to the snout. Underside of legs and groin a mottled yellow, may be lacking in very young individuals. Underside of throat usually mottled.
Sexual Dimorphism
Males have a swollen thumb base.
Habitat
Prefers clear cooler rocky streams without a lot of sediment on the bottom, often found near slower moving pools in these streams. An excellent swimmer, they can navigate underwater in streams that many frog species simply can not.
Seldom found more than a jump or two away from water.
Diet
Feeds primarily on interbrates.
Distribution Range
General range map taken from CWHR.
Museum records taken from following institutions: CAS Herps, MVZ Herps.
Probably present in most of the county except the really high elevations.
Typical Elevation
We do not yet have enough records from distinct localities to calculate typical elevation. We need 9 more distinct localities.
Voice
Seldom heard, this frog primarily calls from underwater. Description of call to come.
Reproduction and Young
Breeds in late spring when the current in the streams have died down from the spring rain.
Recently transormed frogs are very small and easily confused with Sierran Treefrogs, which they often share habitat with.
Additional Information
Images
Unless otherwise noted, all images are of wild specimens in Shasta County.
Please be kind, do not hotlink images and do not use images without permission of the copyright owner.
![[Foothill Yellow-legged Frog]](/images/20sm.jpg)
![[Foothill Yellow-legged Frog]](/images/21sm.jpg)
![[Foothill Yellow-legged Frog]](/images/22sm.jpg)
![[Foothill Yellow-legged Frog]](/images/62sm.jpg)
©Michael A. Peters
Juvenile. Note the extremely weak dorsolateral fold compared to Red Legged Frogs. Note the lack of a fold around the tympanum compared to American Bullfrogs. Near Redding, CA
![[Foothill Yellow-legged Frog]](/images/63sm.jpg)
©Michael A. Peters
Juvenile. Note the yellow on underside of legs and the mottling on underside of throat. Near Redding, CA
Habitat Shots
Unless otherwise noted, these habitat shots are from within Shasta County where this species is known to occur.
![[Foothill Yellow-legged Frog habitat]](/images/23sm.jpg)
![[Foothill Yellow-legged Frog habitat]](/images/64sm.jpg)
©Michael A. Peters
If you look at the high resolution version of the image, in the shadow where the pool meets the rock near the center of the image, you should be able to see the frog. Near Redding, CA
Similar Species
Cascades Frog
The Cascades Frog (Rana cascadae) has a distinct dorsolateral fold and a white jaw stripe.
Oregon Spotted Frog
The Oregon Spotted Frog (Rana pretiosa) is probably extinct in Shasta County. It has upturned eyes, a white jaw stripe, usually has distinct black spots on the back and salmon red underside of legs.
California Red-legged Frog
The California Red-legged Frog (Rana draytonii) does share habitat in some places with the Foothill Yellow-legged Frog but generally prefers still streams and ponds. They have a distinct dorsolateral fold and the underside of the legs are red.
American Bullfrog
The American Bullfrog (Lithobates catesbeianus) is generally a much larger frog with a very distinctive ear fold.
Sierran Treefrog
Very young Foothill Yellow-legged Frogs sometimes share habitat with the Sierran Treefrog (Pseudacris sierra) and it can be difficult to tell them apart. Sierran Treefrogs have a broad stripe through their eye and smoother skin. If the stream has a decent current, Sierran Treefrogs are more likely to swim along the surface of the water or avoid jumping into the water when startled, Foothill Yellow-legged Frogs will generally dive to the bottom.
Species of Special Concern
This species is listed as a Species of Special Concern by the State of California Department of Fish & Game.
If you come across this species, please note that it may be a violation of state law to collect it or even touch it. Federal laws may also apply.
If you can, please do the following:
- Accurately record the location where the animal was found. The best way to do this is with a GPS device.
- Photograph the specimen. Take as many photographs as you can without causing too much stress to the animal.
- Take note of the habitat and its condition. Photographs are good for this, but do not always tell the entire story.
- Take note on any possible threats to the population. For example, if it is one of our threatened native frog species, is there an American Bullfrog population in the immediate vicinity? Are you aware of an American Bullfrog population in a nearby aquatic system? What about erosion? Introduced trout?
- Report the sighting to the California Natural Diversity Database.
It takes a little effort to file a report, but your report may help the necessary agencies protect that population. It is difficult for them to protect populations they do not know about or populations they think are extirpated. Even species of special concern that are currently doing well in Shasta County should be reported. When population declines happen, they tend to happen very fast. Reports of specific localities where a species is known to have occured may help researchers determine survey sites if our population of one of these species does crash.
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