Snarls and Snores

Leopard Frog? Pickerel Frog? This identification question seems to come up quite a bit for people who are listening to frog songs. Citizen scientists who participate in FrogWatch do their surveys at night, so these folks always have to gather data by ear. 

A number of frog species are quite distinct from one another, particularly with a side-by-side recording reminder. There are a few, however, that people tend to have trouble identifying. 

For example, people generally know the Spring Peeper’s common and relentlessly loud peeping calls. What they often find confusing is the Spring Peeper’s ascending trill calls and the calls of the Western Chorus Frog, especially because these two species may be found calling in the same location.

Western Chorus Frog, above and Spring Peeper, below. 

Listen to this comparison of the Western Chorus Frog followed by the Spring Peeper’s trill call. The trilling peeper is much more melodious to human ears because the pitches are not as high as those of the Western Chorus Frog and therefore sound clearer to us. In fact, they fall into the same range as many bird songs. 

Another point of confusion can be the Gray Treefrogs. Up here in NE Ohio, we have Gray Treefrogs but not the visually identical Cope’s Gray Treefrog. Southern Ohio residents have Cope’s Gray Treefrog AND there are locations where both species are present. 

If that’s true for you – or if you’re visiting Cope’s country – you can learn the difference if you’ll graciously grant yourself a little patience. I’ll include an example below and also this link to the Listening in Nature post that features both calls if you’d like to do some additional listening.

And then there’s Leopard and Pickerel Frogs. Some people say, “I don’t even try.” So let’s spend a little time with this comparison and experiment with some approaches you might find helpful in separating these two species. 

First, a quick reminder of some visual similarities and differences. These frogs are about the same size. Leopard Frogs are generally green and the Pickerel Frogs tan, and both have prominent dark spots. The Leopard Frog’s spots appear more random than the paired rows of Pickerel Frog spots. I find this distinction to be very helpful.

Here are Leopard Frog spots...

 ...and here are Pickerel Frog spots.

 

Both species call in April after the Wood Frogs have finished and the Spring Peepers and Western Chorus Frogs have already been calling for perhaps a month. It seems to me that the Pickerels start a little later than Leopards, though I don't know if that's consistently true. I also have not heard both species in the same places, though again, that may not be true elsewhere.

Although The Ohio Frog and Toad Calling Survey states that Pickerel Frogs “utilize the margins of clear, cool streams, woodland springs and seeps, fens, and wet meadows,” this isn’t necessarily true in my corner of NE Ohio. I’ve only found them in lakes, ponds, and marshes so far, so keep that possibility in mind. 

Now about listening. Let’s start with the Leopard Frog. 

They can call underwater, as can Pickerels, so you may not always know exactly where the sound is coming from. Although their calls are often described as sounding like snoring, listen for variation. I’ll give you some examples.

They can make grunting sounds, and sometimes their “snore” can be a rather dramatic roar instead.  





You may hear a relatively smooth, continuous sound or one that has lots of tiny separations in the sound’s flow. I describe it as "eh-eh-eh-eh-eh" and you can see the separations on the sonogram. 

I’ve focused on individual calls and small groups for detail. Now here's a large, glorious chorus at Killbuck Marsh Wildlife Area near Shreve (a little south of Wooster). When I recorded this inspiring chorus (photo below), I was literally standing in the water with them. Could I see them? Not really, but they were never far from my boots as I slowly sloshed through the water.

OK, got it? Now on to the Pickerel Frogs.

Brad Phillips at Erie (County) MetroParks described their song to me as a “snarl,” and I think that’s useful to remember. It’s definitely a smoother sound than those of the Leopard Frogs. (Personally, I think Pickerel Frogs can also sound at times like a growling stomach.)

The songs start softer and quickly become louder. (Imagine snarling "Nyeeaaahh!" at someone.) You can see the contour on the sonogram I’ve included.  The steady band of sound that runs through this sonogram (and recording) is that relentlessly loud chorus of Spring Peepers I mentioned earlier.

Now here's a chorus of several Pickerel Frogs and, of course, Spring Peepers.

A useful way to remember similar calls like these is to try imitating each one. 

If I were to imitate the Pickerel Frog, I would say “errrahh” beginning with my jaw clenched and lips apart, then gradually open my jaw a little and slowly closing it again. "Nyeeaaah" works pretty well, too.

But for the Leopard Frog, I would open my jaw farther before closing it, and I’d also do a “rrrah-ah-ah-ah-ah-ah” at times for the call type that has more spaces.

For both species, try to make the sound as guttural as you can. Don’t sing it; you are growling and snarling. 

Now go back and listen to the frog calls and imitate them as best you can. Improvise as needed - you may find it amusing as well as useful to find the sounds that work best for you. 

Then try immediately to recall what you did and how you did it. You don’t have to do all this in front of anyone, though if you do, you can both break down into uncontrollable laughter afterward. But you will remember the songs better!

Here's a practice track for you: Pickerel Frogs first (accompanied by Spring Peepers) followed by different Leopard Frog calls. 

What was similar? Different? What did you do to create those songs, and can you recreate them now? Actually making similar sounds yourself can be very helpful in remembering because you didn’t just listen - you did something with your own body to create a similar sound. It involves muscle memory. 

OK, Frog Watchers – or should I say, Frog Listeners! Refer back to this post next April if it's beneficial. In the meantime, we still have Green Frogs, Bullfrogs, and the lovely Gray Treefrogs calling, so keep listening...

FrogWatch monitoring protocols

The Ohio Frog and Toad Calling Survey

I’ll include a Google map of where I’ve recorded them so far and also reports from naturalists in the region. I’ll update the map as I get more information. I’m interested in where we have Pickerel Frogs in our region, and you’ll probably want to know where this is an option when you’re doing surveys.