Article
National Geographic Image Collection/Alamy Stock Photo

Hear Me Croak!

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

By Stephanie Warren Drimmer
From the May/June 2020 Issue
Other Focus Areas: Earth and Space Science; Human Impacts
Download and Print

National Geographic Image Collection/Alamy Stock Photo

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

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.

Ann Earley grabs a flashlight. She heads out the door. It’s a quiet spring evening in St. Louis, Missouri. Earley walks down the street. She stops at the edge of a small pond. She checks the time and listens. 

Earley isn’t out for a stroll. She’s here on a scientific mission. She’s a citizen scientist. She’s helping with FrogWatch USA. It’s a project run by the Association of Zoos and Aquariums. FrogWatch volunteers live across the U.S. They help out every year between February and August. They write down frog calls they hear in their area. Scientists use the data. It helps them monitor frog populations.  

It’s important work. That’s because frogs around the world are in trouble. Frogs are amphibians. About one-third of this group of animals is at risk. They could become extinct. Scientists hope to stop that from happening. And volunteers like Earley are helping.

Frogs at Risk

George Grall/National Geographic Image Collection/Getty Images

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 world is home to more than 4,700 species of frogs. They live on every continent except Antarctica. Most frogs spend their lives in wetlands. These are watery spots like marshes, swamps, and ponds. These areas are filled with living things. That includes everything from algae and insects to fish. Nearly half of all threatened plants and animals in the U.S. live in wetlands.

Frogs rely on wetlands to survive. They lay their eggs in water. Frogs live in water as young tadpoles. Adult frogs have special skin. They can breathe through it underwater.

Sadly, wetlands are disappearing. People are drying them out to build cities and farms. The frogs that live there are vanishing too. Pollution from cities and farms is also a problem. Rain and snowmelt can carry pollution to wetlands. It can make frogs sick. All these changes can stress frogs. That makes them more likely to get sick. 

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

Frog Patrol

George Grall/National Geographic Image Collection/Getty Images

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.

The FrogWatch program is trying to help frogs. Anyone can join. That includes kids! Volunteers get training from local FrogWatch staff. They learn what to listen for. Frogs make noises to attract mates. Air vibrates between their lungs and stretchy sacs in their throats. Every species’ call is different.  

FrogWatch volunteers trek out at dusk. They visit wetlands, from neighborhood ponds to large lakes in the wild. They go at least three times each season. They spend three minutes writing down what frogs they hear. They also record how noisy the frogs are. 

The volunteers enter their data into a website. Scientists can review it. The data reveals where different frog species live. Over time, it can show when frogs in an area are in trouble. Sometimes people heard frog calls in the past. But they don’t anymore. That’s a cause for concern.   

Tracking amphibians can help in another way. It can reveal if efforts to protect them are working. Gauza leads a project In Washington, D.C. It aims to restore wetlands. The project works to limit pollution and construction. FrogWatch volunteers listen for frogs at these sites. More croaks mean the animals numbers are rising.

Courtesy of Jennifer Austin

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.

FrogWatch isn’t the only citizen science project helping frogs. Toad Trackers is a group run by the Houston Zoo. It asks volunteers to catch, measure, and count toads in Houston, Texas. Another project is called Global Amphibian Blitz. It has people submit photos of amphibians. The findings are collected on a world map.

Researchers benefit by working with citizen scientists. These volunteers can help scientists collect much more data than they ever could alone. “It’s a team effort!” says Gauza.

video (1)
Activities (5) Download Answer Key
Text-to-Speech