YELLOW-LEGGED FROGIDENTIFICATION

Rana sierrae

Rana boylii

Sierra Nevada Yellow-legged Frog

Foothill Yellow-legged Frog

Slate Creek North of Poverty Hill

Willow Creek

YELLOW-LEGGED FROG IDENTFICATION

Foothill (Rana boylii) and Sierra Nevada (R. sierrae) Yellow-legged Frog identification can be difficult.

Correct identification is critical now that the Sierra Nevada Yellow-legged Frog has been listed as endangered under the Endangered Species Act (April 29, 2014, FR Vol. 79, No. 82, 50 CFR Part 17).

YELLOW-LEGGED FROG IDENTFICATION

We documented field marks (based on current sources) of live Yellow-legged Frogs and reviewed photographs of previously identified frogs. We found that the characteristics can be subtle between species and individuals of each species.

Therefore the biologists at Feather River Ranger District designed this presentation based on our field observations of these two species.

The most reliable feature was the skin texture. However, all characteristics should be combined to support the identification of species.

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiSandpaper-like texture on skin. Big warts/bumps on sides.

Skin Texture

Tributary (A) to Slate Creek, east of Dark Ravine.Willow Creek.

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiDark “splotches” on back. More solid coloring, occasionally

reddish stripes along the “dorsolateral fold area”.

BackPattern 1

Willow Creek Onion Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiDark “splotches” on back. More solid or variable coloring,

occasionally reddish stripes along the “dorsolateral fold area” or even reddish all over dorsal side.

Back Pattern 2

Willow Creek Dark Ravine

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiDorsolateral fold more defined. Dorsolateral fold less distinct.

Dorsolateral Fold 1

Photo by Ben Karin Dark RavineWillow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiDorsolateral fold sometimes less defined.

Sometimes RABO look like they have a more prominent dorsolateral fold, especially when held.

Dorsolateral Fold 2

Willow Creek

Slate Creek

Cedar Grove Ravine

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiStripes on hind limbs lack definition and do not match when when folded together.

Well defined stripes, matching when folded.

Hind Limb Stripes 1

Willow Creek

Trib A east of Dark Ravine

Trib A east of Dark Ravine

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiLeg stripes sometimes are noticeable, but are often off-set rather than fully matching.

Leg stripes not always distinct, especially when reddish color obscures stripes.

Hind Limb Stripes 2

Willow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae – adult Rana boylii -- adultSnout patch absent between eyes. Buff-colored line usually present

between eyes. Buff-colored triangle often seen on metamorphs.

SnoutCharacteristics 1

Willow CreekPhoto by Ben Karin. Dark Ravine

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae -- metamorph Rana boylii -- metamorphsSnout patch absent between eyes. The metamorphs may exhibit a

“buffy triangle” more often than adults.

Snout Characteristics

2

Pine Grove Cemetery Pond

Slate Creek near St. Louis Bridge 2015

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiLower part of iris gold or rose-gold.Dorsolateral fold begins over tympanum.

Lower part of iris is silver. No ridge over tympanum.

Iris Color &Tympanum

Tympanum -- We did not find obvious differences (well defined and smooth in RASI and indistinct and grainy in RABO) as suggested by

field guides.

Photo by Ben Karin, Dark RavineWillow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiToe tips are more pointy than RABO. Toe tips more rounded, almost a

little bulge at the tip.

Toe Tip Color -- The light toe tip characteristic on the RABO and dark toe tip characteristic on the RASI did not seem to be a good field mark to

use for identification.

Toe Tips

Willow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiVentral yellow goes up to top of chest and sometimes up to chin.

Occasionally, we saw that the yellow on the ventral side goes up to upper chest or lower throat; usually extends to lower abdomen.

Ventral Yellow 1

Willow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiYellow extends to upper chest. This yellow pattern was more

typical of RABO. On hind limbs and lower abdomen.

Ventral Yellow 2

Willow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiIf mottling under chin is present, it is darker and more defined (crisp edges) than RABO.

May have mottling under chin. Often not as dark or well defined as RASI.

Chin Mottling

Willow Creek

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiMay have garlic odor, but not always noticeable.

“Burnt-Peanut” odor – not always noticeable either.

Odor

Note: make sure you or your co-worker did not cut up garlic the night before. Or eat a bunch of garlic fries.

Or a PB&J sandwich.

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiTadpole has 2-3 upper tooth rows, 3-4 lower.Tail fin relatively low throughout its extent – does not rise up about midway.

Tadpole is very “toothy”: 5-6 lower tooth rows and 6-7 upper tooth rows.Tail rises about mid way, then tapers.

TadpoleToothrows

& Tail 1

The tail fin shape is a good indicator of species.Take good side photos of tadpoles in a clear container.

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiTail fin relatively low throughout its extent – does not rise up about midway.

Tail rises about mid way, then tapers.

Photo by Gary Nafis (California Herps Website)

Tadpole Toothrows

& Tail 2

We have no photos of RASI tadpoles or their toothrows.

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boylii

The habitat for both species on the FRRD was similar: cobble-bottomed streams.

Habitat in Willow Creek: Intermittent creek

Onion Creek

Habitat

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boylii

Our two populations of RASI are at 5300’ (Pine Grove Pond) and 5500’ (Willow Cr).

Our highest confirmed RABO is 5000’ (Cedar Grove Ravine).

HabitatElevation

Willow CreekSlate Cr (S of Am. House, N of Poverty Hill)

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiFagg’s Reservoir Concow Creek

Habitat

* We assume the RASI breed in Fagg’s Reservoir, however we do not have any record of egg masses

or tadpoles in the reservoir itself. Tadpoles were located less than 100’ upstream of the reservoir in

Willow Creek in 2004.

YELLOW-LEGGED FROGIDENTIFICATIONRana sierrae Rana boyliiWillow Creek Trib A to Slate Creek, west of Dark

RavineBedrock pool.

Habitat

YELLOW-LEGGED FROGIDENTIFICATION

Recommendations

TAKE A LOT OF PHOTOGRAPHS

Get good pictures of:

Adults / Metamorphs:• Side of frog

• Eye and Tympanum• Ventral side

• Front Foot/Toes• Back

Tadpoles:• Pictures of toothrows if

possible (use clear container)

• Get good side picture of tail.

TAKE GOOD NOTES

Why did you call the frog a RABO or a RASI?

• List multiple characteristics that you used to identify the frog

or tadpole

• Describe habitat

• Use multiple identification guides.

YELLOW-LEGGED FROGIDENTIFICATION

LiteratureWestern Reptiles and Amphibians – Peterson Field Guide (Stebbins, R.C. 1985 Houghton Mifflin Co. Boston)

Sensitive Amphibians (5/7/94 draft, L. Mink) Informational sheet

Roland Knapp, UCSB --- e-mail to Colin Dillingham RE: Characteristics of Yellow-Legged Frogs

California Herps webpage www.californiaherps.com

Amphibians of Oregon Washington and BC. Corkran, C., C.T. Thoms. 1996 Lone Pine Publishing, Renton, WA

Feather River RD 2014-2015 Field ObserversJoAnna Arroyo Maria Cisneros

Dawn Garcia Eric MathewsMary Muchowski

YELLOW-LEGGED FROGIDENTIFICATION

Characteristic   Foothill Yellow-Legged Frog (Rana boylii)   Sierra Nevada Yellow-Legged Frog

(Rana sierrae)In order of confidence of identification as based on FRRD Field ObservationsSkin Texture   Warty/bumpy especially on the sides of the

abdomen.   Back skin texture is like sand-paper --- gritty, but not bumpy/warty.

Back Pattern  Will occasionally have reddish coloring along

undefined dorsolateral folds, and/or on sides and/or on rear legs.

  No reddish coloring observed in RASI. Dark splotches (spots without well-defined edges) on back.

Dorsolateral FoldUsually absent. Can appear to be distinct when held in certain

positions. Reddish coloring along the dorsolateral fold lines can make it appear more distinct.

Usually noticeable, but can look diminished when sitting in certain positions, or if they are fat.

Rear Legs -- dorsal

"Matching Stripes"

 Well defined "matching stripes" when legs are

folded. Stripes on upper leg match the stripes on the lower legs.

 Stripes on legs not perfectly matched. Sometimes look fairly close to matching, but usually offset and not as

well defined as RABO.

Snout patch  Generally not a full buffy triangle on adults. Many times just a thin line between and just forward of

eyes. Sometimes absent.  No buffy snout patch.

Iris   Lower 1/2 of iris is silvery gray. Upper iris is gold.   Lower 1/2 of iris is gold or rose-gold. Upper iris is gold.

Toe tips  A little more rounded (bulging) at tip. More

difference in shape rather than in color of the toe tips. Sometimes light-colored.

  More pointy at tip. Sometimes darker toe tips .

Ventral color   Yellow from rear legs to lower abdomen. However, can extend to throat.   Yellow usually goes all the way from rear legs to chin.

Chin Mottling Dark and well -defined markings under chin (crisp edges). Markings under chin are more mottled and the edges seem to “bleed”.

Odor Have an odor, but it does not smell like garlic. Occasionally smells like garlic.

Tadpole ID(we didn’t have much

experience in this) 

Tailfin is wider about midway to tail. Grey-green mottling: cryptic. May also have gold coloring as

base.  Tailfin is even to the tail.

Black (or dark brown) with gold flaking (from literature)

Habitat - Water  From slow-moving wide streams (Slate Creek) to really steep creeks with bedrock and cascading

waterfalls/slides (Tributary A east of Dark Ravine). 

In mountain lakes in the shallower ends with logs or rocks to hide under. Very slow moving creeks (Willow Cr)

associated with a pond/lake for breeding. Along shorelines with sunny margins.

Summary