Spring frog chorus: Where you can hear amphibians’ seasonal song

Every spring, visitors are serenaded by a chorus of frogs emanating from Stillman’s cattail marsh. And almost every person comments, “Listen to those spring peepers.” Guess what?

Almost everyone who says that is mistaken. They are actually the aptly-named chorus frogs.

The name game

Please pay attention to the scientific name of this species, Pseudacris triseriata. I advise this since the species has a variety of common names such as boreal chorus frog, striped chorus frog, Western chorus frog, or midland chorus frog. For the amphibian chorus we have performing at the nature center, I’ll go with the common name used by the Illinois Natural History Survey, Western chorus frog. Interestingly, this genus of frog is only found in North America.

Chorus frog identification

These diminutive singers are quite difficult to spot. Western chorus frogs are only .75 to 1.5 inches in length, with the males being smaller than the females. While they are cream underneath, the background color of their upper surfaces range from brown to gray to olive.

These frogs usually have three dark stripes running down their backs. In addition, they have two lateral strips that run from their nose, through the eyes, and to their tailless rear ends. These stripes vary in size and may be interrupted in places. These variations aside, all chorus frogs have a light line along the upper lip.

Marshland performances

While you need sharp eyes to see these little guys, they are certainly not hard to hear, assuming you are listening at the right time and the right place.

The right place to hear this springtime breeding chorus is near a shallow body of water such as our cattail marsh. The tall cattails provide an elevated perch for the singing males while the water below is a suitable location for the eggs and developing aquatic tadpoles.

Truth be told, this species is not too particular about the habitat they will use for breeding.

You can hear them in flooded agricultural fields, swamps, city parks, suburban neighborhoods, and in ditches lining railroads or busy thoroughfares.

For such a tiny species, chorus frogs can sure make a conspicuous call. I am reluctant to use the word “croak” for the chorus frogs’ soprano vocalizations. The best way to describe it is to think of the sound made when you run your fingernail along the teeth of a comb. Now, plug that call into an amplifier. The repeated calls last one to two seconds and are typically heard in March or April.

A warm spring rain seems to inspire this unseen wetland choir. Given the mild winter we had, we might hear the chorus frogs earlier this year.

Join a frog walk

Stillman Nature Center will hold its first frog walk of the season at 6:30 p.m. Saturday, March 30.

Participants will hike to the bird blind which sits on the edge of the cattail marsh. With any luck, the male chorus frogs will be calling from quite nearby. Join naturalist Lara Sviatko to listen for these tiny frogs.

Dress for the weather and wear shoes that can get muddy. This free event is for ages 8 and older.

Stillman is at 33 W. Penny Road, South Barrington. For details, visit the website or call (847) 428-OWLS.

From eggs to frogs

Male Western chorus frogs will mate with multiple females. Similarly, females will breed with more than one male frog. The female chorus frogs will lay from 500 — 1,500 eggs during the season, normally in clusters of 20 to 300 eggs. The egg cluster will be submerged and attached to weeds, grasses, and other locations along the edge of wet depressions.

The eggs will take three days to two weeks to hatch. It can take anywhere from 40 to 90 days for the tadpoles to grow into frogs. Since amphibians are coldblooded, water temperatures play a major role in the development of eggs and tadpoles. Colder water slows the frogs’ metamorphosis.

Where do they go?

Shallow bodies of water will sometimes dry up after a long, rainless summer. Stillman’s cattail marsh has done so. The ephemeral nature of these wetlands raises the question: Where do the chorus frogs go when the water is gone? As mentioned earlier, Western chorus frogs will use a variety of habitats, including grasslands, forest edges and a variety of urban and suburban settings.

Spring peepers

To be fair, we do have spring peepers (Pseudacris crucifer) in Illinois and they are in the same genus as chorus frogs. As their scientific species name suggests, these tiny (.75 to 1.25 inches) tan or gray frogs are marked with a cross pattern, or ‘X,’ on their backs.

The peepers’ call is a high-pitched rising whistle that some have compared to the jingle of bells.

The male frogs make these calls from branches of trees and shrubs that overhang or grow near woodland pools, this frog’s preferred habitat. Trying to find a peeper after the early spring breeding season subsides is a definite challenge!

This is probably a good thing since small frogs are prey for a variety of animals, including birds, snakes, and larger frogs. Like many types of frogs, these little guys eat spiders as well as flies, ants, and other insects.

Frogs need wetlands

I have long found the word “wetland” to be rather dull, particularly when compared to the illustrative words used to describe particular wet habitats such as bog, marsh, or swamp. It is, though, a convenient umbrella term, as it were, to encompass the wide variety of habitats that are wet for at least part of the year. The term would include the cattail marshes and woodland pools where the frogs, discussed above, can be found.

If you live near a wetland, listen at dusk in the early spring for the unmistakable amphibian chorus. Of course, if the frogs are calling the buzzing of mosquitoes, one of the frogs’ foods, can’t be far behind. Sorry for being a wet(land) blanket.

Mark Spreyer is the executive director of the Stillman Nature Center in Barrington. Email him at stillmangho@gmail.com.