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Frogs make noise by moving air between their lungs and throat pouches called vocal sacs. These sacs can inflate like balloons!


Hear Me Croak!

Why people are trekking out to marshes and ponds to listen for frogs

On a quiet spring evening in St. Louis, Missouri, Ann Earley grabs a flashlight and heads out the door. Down the street, she arrives at the edge of a small tree-lined pond. She stops, checks the time, and listens. 

Earley isn’t out for a casual stroll—she’s here on a scientific mission. She’s a citizen scientist with FrogWatch USA, a project run by the Association of Zoos and Aquariums. Every year between February and August, FrogWatch volunteers around the U.S. write down the frog calls they hear in their area. The data they collect helps scientists monitor frog populations. 

It’s important work because frogs around the world are in trouble. About one-third of all amphibians, including frogs, are at risk of becoming extinct. With the help of volunteers like Earley, scientists hope to stop that from happening.

Frogs at Risk

Spring Peepers live in the eastern region of the U.S. Their call is a high-pitched “peep.”

The world is home to thousands of species of frogs living on every continent except Antarctica. Most frogs spend their lives in wetlands, such as marshes, swamps, and ponds. These watery spots are teeming with living things, from algae and insects to fish. Forty-three percent of threatened and endangered plants and animals in the U.S. live in wetlands.

Frogs depend on these soggy landscapes to survive. They lay their eggs in water. When frogs are young, they live underwater as tadpoles. Adult frogs have special skin that allows them to absorb nutrients and oxygen directly from the water.

Unfortunately, people are draining wetlands, or drying them out, to build cities and farms. And as wetlands vanish, so do the frogs that live there. Rain and snowmelt can also carry pollution from cities and farms to wetlands. That pollution can make frogs sick. All these habitat changes can also cause frogs stress, making them vulnerable to disease. 

Frogs are extremely sensitive to their surroundings. Studying them can reveal the health of the environment, says Rachel Gauza. She’s a biologist at the Department of Energy and Environment in Washington, D.C. “Amphibians are like superheroes who signal when something is going wrong.” 

The Life Cycle of a Frog

Frogs depend on wetlands to survive. Their presence also benefits the plants and animals that live in these areas.

  1. Egg: Frogs lay eggs in the water. They clump together in a jelly-like substance. 
  2. Tadpole: These fish-like creatures hatch from the eggs. By eating algae, they help keep the water clean. 
  3. Froglet: Tadpoles sprout legs, lose their gills, and start to develop lungs. 
  4. Adult: Frogs eat large amounts of insects. That helps keep the mosquito population from growing out of control. 
  5. Tadpoles, froglets, and adult frogs are also food for other animals, such as fish, snakes, and birds. 

Think: How might wetlands be different if frogs were to disappear?

Frog Patrol

Northern Leopard Frogs are found across the U.S. and Canada. They make a rattling snore-like call. 

The FrogWatch program is trying to help frogs. Anyone can participate—including kids! To learn what to listen for, volunteers receive training from local FrogWatch staff. Frogs make noises to attract mates. The calls are produced when air vibrates between their lungs and stretchy sacs in their throats. Every species’ call is different. 

At least three times each season, FrogWatch volunteers trek out to wetlands just after dusk, from neighborhood ponds to large lakes in the wilderness. They spend three minutes writing down the frogs they hear and how noisy the frogs are.

The volunteers submit their observations to a website that scientists can access. The data reveals where different frog species live. Over time, it can show when frogs in an area are in trouble. For instance, if people heard frog calls in the past and they don’t anymore, that’s a cause for concern. 

Monitoring amphibians can also help people judge the success of conservation efforts. In Washington, D.C., Gauza leads a project to restore wetlands by limiting pollution and development. FrogWatch volunteers listen for frogs at these sites. If they hear more croaks, they can tell that Gauza’s efforts may be working.

Biologist Rachel Gauza holds a spring peeper that she found on a FrogWatch outing.

Teaming Up

American Bullfrogs are common across the country. They make a low-pitched “burp” sound!

FrogWatch isn’t the only citizen science project devoted to monitoring amphibian populations. Toad Trackers, a group run by the Houston Zoo, asks volunteers to catch, measure, and document toads in Houston, Texas. A project called Global Amphibian Blitz invites people to submit photos of amphibians. The findings are collected on a world map. 

Citizen scientists like the FrogWatch volunteers can help scientists collect much more data than they ever could alone. “It’s a team effort!” says Gauza.

Continue the Learning Journey
Animal Spotting

Collect data about animals in your area. 

Now it’s your turn to observe wildlife! Think about somewhere safe in your community where you can make observations with an adult. You may even be able to make observations from inside by looking out a window! Check out the slideshow above to get started as a citizen scientist! You will need a clipboard or something to write on, a pencil, paper, a stopwatch or timer, and an audio recorder if you have one.

Amazing Amphibians

Watch a video about the characteristics of amphibians.

A scientist in the article says, “Amphibians are like superheroes who signal when something is going wrong.” After watching the video, list the fantastic features of amphibians. Then use your list to create an amphibian superhero! Here are a few things to consider:

  •  What is your superhero’s name?
  •  What powers does your superhero have?
  • What problems does your superhero solve?
  • What does your superhero look like?

Draw your superhero! Then write a short description of how your amphibian superhero makes the world a better place.

Frog Speak

Play a fun science game about frog calls.

Go on a virtual citizen scientist trip with the game above. How many frog sounds can you match with the right type of frog? Challenge a friend or family member to try out the game. When you’re done, chat about these questions:

  • What do you think was the funniest-sounding frog call?
  • What was your biggest challenge playing the game?
  • What other challenges do you think citizen scientists would face on a real field expedition?

This article was written by Stephanie Warren Drimmer for SuperScience magazine.

Image Credits: National Geographic Image Collection/Alamy Stock Photo (header); George Grall/National Geographic Image Collection/Getty Images (spring peeper);  blueringmedia/iStock/Getty Images (diagram); (heron); George Grall/National Geographic Image Collection/Getty Images (northern leopard frog); Courtesy of Jennifer Austin (Rachel Gauza); Kate Francis (Animal Spotting);