Foothill Yellow-legged Frog

Rana boylii

Yellow-legged frog tracks and penny for size. Photo by Kim
        A. Cabrera. Tracks found along Eel River near Redway, CA.
        January 2001.

Foothill Yellow-legged Frog Tracks


Natural History of Foothill Yellow-legged Frogs

                  yellow-legged frog. February 3, 2001. Photo taken
                  along Eel River near Redway, California by Kim A.
                  Cabrera. Foothill yellow-legged frogs are found near streams and rivers. They will come out on the banks to sun themselves, but dive to the bottom if a predator or a threat approaches. They stay still along the river bottom and their color helps camouflage them there. The underside of the hind legs and the abdomen are usually yellow. The younger frogs don't have the distinctive yellow coloring right away, but acquire it as they grow older. The frog in this photo had very faint yellow coloring on its legs. The skin is usually granular in appearance. These frogs breed between mid-March and early June. They range from the Cascade Mountains of Oregon all the way south to the San Gabriel River near Los Angeles.

This species is a California Species of Special Concern. These frogs are losing habitat all over the state. There are many threats to the continued survival of the species in many places across their range.

This is the left hind track of a yellow-legged frog. The tips of the toes are not globular or bulbous like those of the Pacific treefrog. (Pacific treefrogs have toe pads on the tips.)  Yellow-legged frogs have toes that are more pointed than those of the Pacific treefrog. This track was found in fine river silt along the Eel River near Redway, California.  Penny for scale is 3/4 inch across.

Hind track
                    of yellow-legged frog. Note straight ends of toes.

Rana boylii egg mass. Photo copyright Kim A.
I found a place in the river where there were many egg masses deposited. I counted 9 the first day. I returned the next day and found a total of 14.
underwater egg mass. Photo copyright Kim A.
A small egg mass underwater in the Eel River
yellow-legged frog egg mass. Photo copyright Kim
                  A. Cabrera
This egg mass was deposited on the downstream side of a rock, which helps protect the developing eggs from the current.
small submerged egg mass. Photo copyright Kim A.
Close up showing one of the 14 egg masses
egg mass attached on downstream side of a rock.
                  Photo copyright Kim A. Cabrera

Each frog egg is encased in an envelope of jelly, which protects the growing embryo.

large foothill yellow legged frog egg mass. Photo
                  copyright Kim A. Cabrera
Each one of these eggs will hatch into a tiny tadpole. It takes between 5 and 31 days for them to hatch.
freshly deposited egg mass. Photo copyright Kim
                  A. Cabrera
The eggs will hatch faster in warmer water. The river current helps provide oxygen to the developing eggs.
Rana boylii egg mass with creeping water bug on
                  it. Photo copyright Kim A. Cabrera
Predators can eat the eggs and there are many predators! This photo shows a creeping water bug (Ambrysus mormon) trying to eat some eggs.
frog eggs. Photo copyright Kim A. Cabrera
The eggs may become covered in silt, but this helps to camouflage them.
two frog egg masses clustered underwater. Photo
                  copyright Kim A. Cabrera
Two egg masses were attached to this large rock.
A couple of yellow-legged frogs in amplexus.

Personal Notes on Foothill Yellow-legged Frogs

These frogs are fairly common where I live in California. When walking along creeks with gravel or cobble banks, it is sometimes startling when one of these frogs leaps into the water and dives to the bottom. They are hard to see amongst the rocks and their sudden appearance and disappearance is marked only by the distinct 'plop' as they hit the water. Unless you are looking right at the frog, all you hear is the sound. I occasionally find the egg masses left by these frogs. The tiny eggs are visible in their individual globs of jelly. It doesn't take long before the eggs begin to take on the shape of a tadpole. They sometimes wriggle when they are still inside the jelly envelope. Note the shape of the toes in this photo. Compare them to those of the Pacific treefrog on the treefrog page. Young yellow-legged frog. Photo by Kim A.
                    Cabrera. February 3, 2001.
yellow legged frog on the river's edge. Photo
                    copyright by Kim A. Cabrera 2008.
A young yellow-legged frog at the edge of the Eel River.
two egg masses attached to rocks. Photo
                    copyright Kim A. Cabrera
Yellow-legged frog egg masses attached to rocks in the Eel River
Yellow legged frog. Left hind foot. Photo
                    copyright by Kim A. Cabrera 2008.
The left hind foot of a yellow-legged frog. Frog was released unharmed after posing for these photos.
Yellow legged frog. Right front foot showing
                    missing toe. Photo copyright by Kim A. Cabrera
This frog was missing part of one front toe. Possibly due to an attack by a predator. Right front foot palmar surface.
Yellow legged frog. Right hind foot. Photo
                    copyright by Kim A. Cabrera 2008.
The palmar surface of the right hind foot. Notice the small bumps, called tubercles. These show up only in very fine tracks.
The frog was released unharmed after these photos were taken.
Yellow legged frog. Photo copyrght by Kim A.
                    Cabrera 2008.
Yellow-legged frog on the river's shore. There were many frogs along the edge of the water on this late summer day.
small yellow legged frog on my thumb. Photo
                    copyright Kim A. Cabrera
A small yellow-legged frog on my thumb.

yellow legged frog in the sun. Photo
                      copyright by Kim A. Cabrera 2008.

A foothill yellow-legged frog enjoying the sun on a warm summer day along the river.



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Updated: March 26, 2018