Right now, spring peeper sounds are the loudest part of that chorus of spring frogs... at least in our area. We have been hearing the spring peepers peeping for the last week. When I hear the spring peepers call, I delight in thinking about the way they makes those calls. The following photos of spring peepers peeping, as well as video of spring peepers, are my attempt to show how the spring peepers make those spring frog sounds.
This is a photo of a calling frog.
Here is a video of a spring peeper calling. Notice the way the frog forces air into its vocal sac as it calls and how the sac partially deflates and the frog's belly expands in preparation for the next "peep". Keep in mind the vocal sac also functions as a resonating chamber.
Video of a spring peeper calling.
Did you see the frog's belly lift off the twig every time he forced air into his expandable throat bubble? In this video clip the spring peeper is joining with a chorus of frog sounds in the background.
Here is a slow motion video of the spring peeper as it sings.
Since the frog sounds are slowed down to 1/4 speed, they sound much lower. The slow motion video does allow a person to better visualize the flow of air from one air sac to other.
My photos make the spring peeper look too big. They are very small frogs. Here is a photo of a spring peeper on an oak leaf.
Here is a photo of a spring peeper that is taking a break from calling.
I reckon the little frogs aren't so cute when they are all inflated with air while they are singing.