Frog, Toad, and Treefrog Identification Guide

Citizen Monitoring of Wisconsin’s Frogs

byWisconsin Audubon Chapters

Randy Korb, Project DirectorTraining Guides by Mary Linton

This guide will help you identify the Wisconsin frogs, toads and treefrogs that might be active during salamander sampling. Two other guides are also available: a guide to Wisconsin’s salamanders, and a guide to the Protocols for the citizen salamander monitoring project.

The guides are in PowerPoint, a presentation software made by Microsoft. You move through the guide by clicking your mouse or touchpad until you see “THE END”.

There are many other good resources available, and we will list some good sources at the end of this guide.

Purpose of this Project

• Wisconsin has a long-term and successful monitoring program for frogs, toads and tree frogs, the members of the Class Amphibia that have males that call during mating . They use the calls of these amphibians to verify their presence in habitats all over the state.

• Salamanders, the other large group of the Class Amphibia, don’t make mating calls, so cannot be monitored simply. This project seeks to begin a systematic monitoring of salamanders that will add to what is already known about their populations in Wisconsin. In specific, your efforts will help verify distributions of salamanders and fill the large gaps of knowledge in areas where salamander surveys have not been conducted.

• The data you collect will help preserve and protect Wisconsin’s salamanders.

Amphibians come in two types

those without tails those with tails

These belong to the Order Anurawhich includes Frogs, Toads and Tree Frogs

The juvenile stage is called a Tadpole

Clyde Peeling

These belong to the Order Caudatawhich includes Salamanders, Newts

and MudpuppiesThe juvenile stage is called a Larva

Missouri State Biology

While you are out looking for salamanders, you will also encounterthe tailless amphibians – the Anurans. That data will also increase

our knowledge of Wisconsin’s amphibians and the protection of the vital habitat that salamanders use. So, it would be great if all could learn to identify and record the presence of Wisconsin’s

frogs, toads and treefrogs.

Order AnuraAnurans divide into three families

Hylidae: TreefrogsWestern Chorus FrogBlanchard’s Cricket FrogSpring PeeperEastern Gray TreefrogCope’s Gray Treefrog

Ranidae: True Frogs

Mink FrogBullfrogPickerel FrogNorthern Leopard FrogGreen FrogWood Frog

Bufonidae: Toads

American Toad

Some characteristics useful for identifying Anuran species:

1. Are there swollen toepads (useful for climbing)? These are the tree frogs.

2. Skin texture and presence of large skin glands

3. Color patterns

Spots

Background

Masks

Stripes

4. Some folds in the skin

Dorsolateral fold from eye to hind leg

Tympanic fold from eye, aroundtympanum, to front leg

Tympanum

5. And, of course, size

Let’s sort out Wisconsin’s frogs first, then talk about when you might encounter them in your pond. The sorting willInvolve several questions (a dichotomous key to field biologists).

American Toad

1. Is there a paratoid gland present?

a.YES! Family Bufonidae with our only representative, the American Toad, or Bufo americanus

b. No. Go to question 2 on next slide.

The American toad is a medium sized anuran (2-3.5 inches) and is identified by itsrough skin and paratoid gland. It will not give you warts to handle the toad, butyou will be able to feel how that rough thick skin helps them retain water so theycan live far away from water – like in your garden.

2. Are there suction cups on the toes?

a. YES! The treefrogs in the family Hylidae. Wisconsin has several speciesof treefrogs. Go to question 3 below to begin to sort them out.

b. NO. The true frogs in the family Ranidae. We will get to those whenwe come to question 7 in three slides.

3. Are the suction cups wider than the toes?

a. YES. Proceed to question 4 on the next slide.

b. NO. Proceed to question 6 in two slides.

4. Is it a very small tan frog with a darker X marking on the back?a. YES! The Spring Peeper, Pseudacris crucifer.

The Spring Peeper is one of Wisconsin’sSmallest frogs (0.7 to 1.1 inches). They live inMoist woods and their shrill “peep” can beHeard in wetlands in and near those woods.

b. Not colored as in 4.a., go to question 5 below.

5. a. A small (1.5 – 2 in. )green-brown frog with white spots below the eyes – theEastern Gray Treefrog, Hyla versicolor.

b. A small (1.25 – 2 in.) green-brown treefrog with no whiteSpots under the eyes – Cope’s Gray Treefrog, Hyla chrysoscelis.

Don’t let the above pictures deceive you! These 2 very closely related frogs can both change their colors from brown to green and back to match their backgrounds. The eastern graytreefrog does tend to have a bit more mottling than the Cope’s. They live anywhere with places to climb and wetlands for breeding. Perhaps you’ve seen them on your house, boat, etc.

[You got here from 3.b. Suction cups are not wider than the toes.]

6. a. A very small frog (0.7 to 1.2 in.) with a striped pattern on the back – Western Chorus Frog, Pseudacris triseriata.

The Western Chorus Frog is as small as the SpringPeeper and breeds at the same time, but the chorusfrog’s stripes make it easy to distinguish. The call sounds like that produced when running yourfingernail over the teeth of a plastic comb.

b. A very small frog (0.7-1.2 in.) with a small brown triangle on its head (between the eyes) – Blanchard’s Cricket Frog, Acris crepitans blanchardi.

The Blanchard’s Cricket Frog is Wisconsin’s only endangered amphibian It was abundant in southernWisconsin until the 1970’s, then experienced a rapiddecline. The call sounds like metal balls clickingtogether. They like to breed in permanent water withlots of vegetation.

[You got here from 2. b. No suction cups on the toes.]

7. Does it have a dorsolateral fold on the back?

a. NO! Go to 8 below.

b. YES. Go to 9 on the next slide.

8. Is there a prominent tympanic fold between the eye and forelegs?

a. YES! The Bullfrog, Rana catesbiana.

The bullfrog is Wisconsin’s largest anuran. It is green to olive colored with a large tympanum and tympanic fold. Their tadpoles take 2 seasons to mature, so bullfrogs are always found in permanent waters. Their “jug-o-rum” call is classic.

b. NO. The Mink Frog, Rana septentrionalis.

The mink frog has dark mottling on an olive-brown background.The skin has a distinctly musky smell, so if uncertain, give it a sniff.Mink frogs live only in northern Wisconsin in association with lakesand rivers.

Twingroves.district96.k12

Museum.gov.ns.ca

[You got here from 7.b. Has a dorsolateral fold on the back.]

9. What are the spots like on the frog?

a. Large spots on body and legs. Go to 10 below.

b. Small or no spots on body. Go to 11 on next slide.

10. a. Medium-sized frog (1.75-3.25 in.) with squarish spots, yellow on the thighs – Pickerel Frog, Rana palustris.

The pickerel frog has dark large rectangular spots on a green-brownbackground But notice the yellow peeking through at the bend of the hind leg. The call of the pickerel frog is a low short snoring sound. You must listen carefully to hear it.

b. Medium-sized frog (2 – 3.5 in.) with roundish spots with no yellow on the thigh – Northern Leopard Frog, Rana pipiens.

The N. Leopard Frog has large dark dark spots on a green-brownBackground. The call is a loud snore broken by clucks and croaks. A species that is still common but declining significantly.

[You got here from 9. b. Small or no spots on the body.]

11. a. Small frog (1.5 – 2.5 in.) with a dark mask behind the eye – Wood Frog, Rana sylvatica.

A tan-brown frog with a dark mask that includes thetympanum. The call sounds like quaking. Wood Frogslive in moist woods and breed in ephemeral ponds formedby snow melt and spring rains.

b. Medium-large frog (2.4-3.5 in.) with no mask – Green Frog, Rana clamitans.

The green frog has small dark spots on a green-brownbackground. Some people confuse the green frog withbullfrogs. The green frog has a strong dorsolateral fold. Likethe Bullfrog, the tadpoles live for 2 seasons, so the green frogmust breed in permanent waters. The call sounds like aplucked banjo string.

Cortland Herpetology Collection

OK, maybe a summary would be helpful here:

1.Bufonidae – has paratoid gland behind the eye.American Toad

2. Hylidae – does not have a paratoid gland, has suction cups on their toes.Spring Peeper: suction cups wider than toes, a very small tan frog with a

dark X on its back.Eastern Gray Treefrog: suction cups wider than toes, a small green-brown frog

with some darker skin mottling, with a white spot under the eye.Cope’s Gray Treefrog: suction cups wider than toes, a small green-brown frog

with much less mottling on skin than the Eastern Gray treefrogand no white spot under the eye.

Western Chorus Frog: Suction cups NOT wider than toes, a very small frog with a strong stripe pattern on its back.

Blanchard’s Cricket Frog: Suction cups NOT wider than toes, a very smallfrog with a small brown triangle between the eyes.

3. Ranidae – No paratoid gland, no suction cups on toes. May havea dorsolateral skin fold.

Bullfrog: NO dorsolateral fold, a very large frog with a prominent tympanic fold.

Mink Frog: NO dorsolateral fold, a medium frog with strongskin mottling and a musky smell.

Pickerel Frog: Has dorsolateral fold, a medium frog with largesquarish spots and yellow on the thighs.

Northern Leopard Frogs: Has dorsolateral fold, a medium frog with large roundish spots and no yellow on thighs.

Wood Frog: Small frog with dorsolateral fold and a dark maskbehind the eyes.

Green Frog: Largish frog with dorsolateral fold and a green-brownbody with small dark spots.

There are three confusing pairs. Here are hints about how to tell them apart:

Bullfrogs and Green Frogs – Green Frogs have a dorsolateral fold andcoarser skin.

Cortland Herpetology CollectionTwingroves.district96.k12

Bullfrog Green Frog

Northern Leopard Frogs and Pickerel Frogs – Look at the spot shapeand yellow on the thigh.

Pickerel Frog Northern Leopard Frog

The Gray Tree Frogs are highly variable, so can be confused easily. The call is the only sure-fire way to tell them apart. But – check for the whitespot.

Cope’s Gray Treefrog

Eastern Gray Treefrog

When will I see these frogs at my pond?

Early Breeders: March and AprilWood Frog, Western Chorus Frog, Spring Peeper, and Northern Leopard Frog

Late Spring-Early Summer Breeders: May to mid-JulyNorthern Leopard Frog (May and a little June), Pickerel Frog, American Toad, Eastern Gray Treefrog, and Cope’s Gray Treefrog

Summer Breeders: June, July, and AugustBlanchard’s Cricket Frog, Mink Frog, Green Frog and Bullfrog

And, of course, any frog that lives in the water through the summer, such as the bullfrog and mink frog, will be seen at the pond all summer.

Frog tadpoles can be VERY difficult to tell apart. For this study, you should able to distinguish toad tadpoles from Rana tadpoles, and then each of thetreefrog tadpoles. Here’s a way to sort tadpoles:

TADPOLES

1. Where are the eyes?

a. On top of the head (dorsal), Go to 2 below.

b. NOT on the top of the head, go to 3 on the next slide.

2. a. Very dark body, clear tail fin – American Toad.

b. Not as in 2.a. – Rana.

American Toad

Pickeral FrogNorthern Leopard Frog

Green Frog

Pwrc.usgs.gov/tadpoles

[You got here from 1.b. Eyes not on top of head]

3. How much of tail fin is mottled?

a. Most of the tail, go to 4.

b. Only a small part or none, go to 5

4. a. Tail has a red-orange tint, mottled all the way to the tail muscles –Gray Tree Frogs (not possible to tell Cope’s from Eastern)

b. Tail fin not red-orange, tail fin clear next to tail muscles – Spring Peeper.

Clear, unmottled area

pwrc.usgs.gov/tadpoles

fin

tail muscles

pwrc.usgs.gov/tadpoles

[You got here from 3.b., only part or none of tailfin mottled.]

5. a. Large dark tail tip – Blanchard’s Cricket Frog

b. Usually clear tail fin, tail musculature bi-toned: dark on top,light below – Western Chorus Frog.

umesc.usgs.gov/terrestrial/amphibians

Two toned tail muscles

pwrc.usgs.gov/tadpoles

Tadpoles can be difficult to identify, especially when young.

The groups that should be fairly easy to ID are:1. American Toads2. The Genus Rana: you will not ID the species of true frogs.3. The Gray Treefrogs4. The Western Chorus Frogs5. Blanchard’s Cricket Frogs

Spring Peepers are pretty variable, so may not be easy to identify.

And, depending on where you are, you may not catch some of these.

Wisconsin’s amphibians are not evenly distributed across the state.

You can discover what has previously been seen in your area by checking the Wisconsin Herp Atlas. It can be found on-line at:

www.uwm.edu/dept/fieldstation/herpetology/atlas/atlas.html

Why not take some time to check the atlas out now?

----- first click on the hotlink above. ------when the Herp Atlas home page appears, click on “Species Accounts”, then on a species from the list on the left margin.

Make special note of the species not strongly represented in your area.

Feel free to review this presentation as often as you wish.

Here are some other great resources:

Books Amphibians of Wisconsin by Rebecca Christoffel, Robert Hay and Michelle Wolfgram.

can be viewed or purchased on-line at:http://dnr.wi.gov/org/land/er/herps/amphibians

A Field Guide to Amphibian Larvae and Eggs of Minnesota, Wisconsin, and Iowa by Jeffrey R. Parmalee, Melinda G. Knutson, and James E. Lyon

can be ordered from the US Geological Survey (1-800-553-6847 or 703-487-4650or contact the author at melissa_knutson@fws.gov).

Amphibians and Reptiles of the Great Lakes Region by James H. Harding.-available from Amazon, or ordered from your favorite local bookstore.

Websites:EEK (Environmental Education for Kids) by the Wisconsin DNR [http://dnr.wi.gov/eek]Wisconsin Frog and Toad Survey [http://inventory.wiatri.net/FrogToadSurvey]Frog Calls [http://www.midwestfrogs.com]

The End

Gallery.cce.cornell.edu