Music of the Night: Frog Calls

Figure 1: Gray Tree Frog

Figure 1: Gray Tree frog calling. Photo by: David L. Ross

One of my favorite sounds in the world is calling frogs. It is a happy sound that reminds you that warm, summer days lie ahead.

If you have never heard them, take some time to go to a pond, water filled ditch or anywhere with long-standing still water around sunset and just listen. You might even have heard the Gray Tree Frog (Figure 1) in your yard. Sit quietly and enjoy the music. There is no talking allowed or you might scare them silent.

In Illinois, we have 21 species of frogs and toads1. We don’t have time to cover all of them, so I put together a table of the species of both frogs and toads that have the widest distribution across the state and when you might hear them.

Figure 2: Western Chorus Frog Calling

Figure 2: Western Chorus frog calling with single air sac. Photo by Michael Benard

Depending on how far north or south you are or how warm the season is, timing might vary a bit. Two of my personal favorites are the Gray Tree Frog (Figure 1) and the Spring Peeper (Figure 3), and I’ve heard both already this year. To listen to example calls from these and other species from across North America go to the USGS Patuxent Wildlife Research Center Frog Quiz website.

Species Name Breeding Time
American Toad Bufo americanus mid April- early May
Fowlers Toad Bufo fowleri late April to late June
Cricket Frog Acris crepitans late April to August
Gray Tree Frog Hyla versicolor and Hyla chrysoscelis late April to August
Spring peeper Pseudacris crucifer late February through May
Western Chorus Frog Pseudacris triseriata mid February through May
Plains leopard Frog Rana blairi March through April
Bullfrog Rana catesbeiana April through August
Green Frog Rana clamitans May to September
Southern leopard Frog Rana sphenocephala late February to mid-April
Northern Leopard Frog Rana pipiens March through May

Have you ever wondered how such a big sound comes out of such a little body? I know I have. It may surprise you but frogs and toads make many of their calls with their mouths closed. They take in air and push it back and forth between their lungs and mouth. The air travels over their vocal cords making sound. Size of the frog/toad, vocal cord vibration, and speed of air movement all affect how the call sounds.

Figure 3: Spring Peeper

Figure 3: Spring Peeper Photo by Michael Benard

Frogs and toads also have a vocal sac that helps resonate the sound when inflated. Only males have this sac, and depending on the species, they can have one or two2 (See figures 2 and 4).

Figure 4: Southern Leapord Frog

Figure 4: Southern Leapord Frog calling with two air sacs. Photo by John Harrod

So why do they call to begin with? What you hear is the males calling out in hopes of serenading the females to come to where they are. This is when the females will lay their eggs and the males want to be the one to fertilize them. Depending of the species, eggs can be laid in long strings, small clumps, or large masses that can float near the surface or be submerged closer to the bottom (See figures 5 and 6).

Figure 5: Frog Eggs

Figure 5: Frog eggs laid in masses. Photo courtesy of

Toads tend to lay in strings while frogs lay in masses. These eggs will quickly hatch into tadpoles and either develop into frogs/toads that summer or overwinter as tadpoles to develop later.

Figure 6: Toad Eggs

Figure 6: Toad eggs laid attached to a leaf. Photo courtesy of

Frogs and toads are members of an order of animals called Anurans1, and sadly many are in danger of becoming extinct worldwide and that includes some species in our own communities3. Some big reasons for their decline include pollution, habitat loss, climate change and the fungus-caused disease Chytridiomycosis.

Monitoring frog populations is very important. Researchers can see if frogs in an area are in trouble and hopefully find out why. It’s hard to keep track of frogs across the nation so one of the most helpful resources researchers have is YOU!

The USGS North America Amphibian Monitoring Program

The USGS North America Amphibian Monitoring Program is a citizen science initiative that coordinates people across the country to monitor for frog/toad activity.

You can be a part of helping our frogs and toads by participating in the USGS North American Amphibian Monitoring Program (NAAMP) or Frog Watch. Both are citizen science monitoring programs that coordinate people across the country to monitor for frog/toad activity. These types of volunteer opportunities are a lot of fun and do not have to be more than a few nights a season.

NAAMP has predesignated areas for frog monitoring so that those sites can be monitored long-term. At NAAMP’s website you can look at species detection maps, find routes that need your help and contact your local coordinator.

If you are interested in becoming a team member of the Illinois NAAMP contact Natalie Marioni, the Illinois coordinator, at . She has told me that the Illinois chapter is undergoing some changes so volunteering is not available this year. If you are interested, keep checking in to see when routes are established so you can be one of the first to snatch up good sites and routes.

Frog Watch

Frog Watch is part of the Association of Zoos and Aquariums and is set up so you collect and report data on frogs and toads in your area of choice.

Frog Watch is part of the Association of Zoos and Aquariums and is set up so you collect and report data on frogs and toads in your area of choice. You can become and member and get training by joining a local Frog Watch chapter or starting one of your very own. Whichever program you decide to join, get your friends and family to help too. Make it a family adventure!

Check out the Frog Watch and NAAMP websites and be part of saving our frogs and toads!

  1. Phillips, C.A., R.A. Brandon, and E.O. Moll. 1999. Field guide to amphibians and reptiles of Illinois. Illinois Natural History Survey Manual 8. 98-139.
  1. “Call of the Wild” Wading into Wetlands NatureScope. National Wildlife Federation. Web 1 April. 2015. <>
  1. “Illinois Threatened/Endangered Species. 2001.” Illinois Department of Natural Resources. Web. 1 April. 2015 < species list.pdf>.
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