Scientists say frogs are one of the first "canaries in the coal mine" for climate change. That’s because they absorb a lot of what’s in the environment through their skin.
Because frogs are so vulnerable, scientists pay careful attention to where they live and breed. At Webster University, faculty and staff have identified five separate species of frogs in a two-acre bio-retention pond sandwiched between a campus parking garage and Interstate 44.
For Earth Day, Webster researchers will train people how to identify local frogs by their calls during a walk around the pond. Afterwards, they’ll share the data they collect with a citizen science program called FrogWatch USA.
“I think that studying the frogs at Webster shows how bad it can get and how good it can be,” said biology student Katelyn Sullens, who helped organize the event.
Here are the five frogs the researchers have identified in the pond, and how to find them in your own backyard. For optimal listening conditions, find a source of clean water on a warm night, with plenty of bugs around that the frogs like to eat. Try not to use your flashlight — you’ll freak the little guys out with the light — and tread quietly, Sullens said.
"Wait two minutes, and then listen for three. It gives them a chance to adapt," Sullens said.
The sound clips of each frog are provided by the Upper Midwest Environmental Sciences Center in La Crosse, Wis., an arm of the U.S. Geological Survey.
Habitat: Lakes, rivers and marshes.
Look for: She’ll be the biggest frog in the pond — the American Bullfrog is the largest frog in the state. Can be green, olive or brown with spots or blotches.
Sounds like: This frog’s call is low and monotone, like she owns the place.
Habitat: Near water with thick undergrowth. These frogs are one of the earliest to come out in the spring.
Look for: A teeny pink, gray or tan frog with a dark X on its back.
Sounds like: High-pitched and shrill, almost a squeaky chirp.
Western chorus frog
Habitat: Prairies and agricultural lands or flood plains.
Look for: Small, less than two inches long. Gray or tan with three wide, dark stripes or spots on her back.
Sounds like: Melodic, soothing croaks.
Habitat: Creeks, rivers and flooded ditches, but may head into the woods and pastures to hunt for tasty insects.
Look for: This guy is green or brown with spots and two lines down his back. He’ll have a white line along his upper lip.
Sounds like: Throaty, “almost like a laugh,” said Ruby Parks, a Webster sophomore.
Cope’s gray tree frog
Habitat: These guys love their trees and can be found in wet woodlands, fishless ponds and swamps. You’ll hear them best between April and July.
Look for: Color varies between gray, green and brown. Most gray tree frogs have a white spot under their eye.
Sounds like: Deep, constant, almost musical.
Want more? Visit the USGS’ website to see a longer list of frogs in the Midwest, or check out the FrogWatch USA chapter at the Saint Louis Zoo. The FrogWatch training at Webster University begins at 7 p.m. on Fri., April 22.
Follow Durrie on Twitter: @durrieB.