Are Frogs Bioindicators?

Frogs are good bioindicators of their environments meaning that they can alert scientists that something is wrong.

Bioindicators are species that show a response to problems in an ecosystem such as chemicals, pesticides, and pollution. Bioindicators may display deformities or die due to the changes in their environment, alerting scientist that action needs to be taken.

You may have heard the expression a canary in a coal mine. Canary’s were sensitive to carbon monoxide and died when they inhaled it, warning the miners they needed to get out of the mine as well.

Frogs are the canaries of the aquatic world. They can be used as a tool to measure water quality and the health of the ecosystem.

Why Are Frogs Good Bioindicators?

Frogs live in aquatic habitats and have very thin permeable skin. Their skin allows them to breathe and take in nutrients from the water.

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However, it also means they easily absorb pollutants, hormones, and chemicals that run into the water.

Frogs have shown a sensitivity to many chemicals that we use in the environment. Some of the chemicals that enter the waterways cause changes in the frog’s DNA or RNA. This has caused some deformities that may seem shocking.

Tadpoles are a natural filtration system. They feed on algae and take in the water of their habitat. Like fish, they are in the water 24/7.

When tadpoles go through metamorphosis they retain chemicals in their bodies. As adult frogs, they continue to interact with the water for food and habitat.

Metamorphosis is a complex set of changes that are regulated by the tadpole’s endocrine system. Chemicals in the water may disrupt the frog’s natural hormone release telling its body to make a change.

When this happens normal development may be altered. This is when we see extra or no limbs on the body.

In addition, adult frogs may combine a terrestrial and aquatic lifestyle, such as tree frogs who come down to mate and spawn in water. These species may absorb different chemicals depending on where they are living.

Bioindicators Provide Wake Up Calls

One wake-up call for scientists has been finding frogs with extra limbs, fewer limbs, or other gross physical deformities.

Biologist Judy Helgen, was working for the Minnesota Pollution Control Agency in 1995 when she was alerted to frogs with gross malformations at New Pond in Minnesota.

Helgen and her team took samples of the water and examined frogs in various life phases. They concluded that some chemical was causing the deformities and they linked it to nearby wells.

This bioindicator was very important for human health as it was discovered many of the area wells were also polluted. Helgen’s team learned that a charcoal filter reduced the problem and these were placed in people’s wells.

I highly recommend reading Heglens book “Peril in the Ponds — Deformed Frogs, Politics, and a Biologist’s Quest.” which talks about her journey trying to trace the reasons for the malformed frogs and the bureaucratic entanglements.

Since Helgen’s landmark study malformed frogs have shown up in 44 US states and 3 Canadian provinces. A wide variety of frogs and toads have been affected showing that one species is not necessarily more sensitive or resistant than another.

What Chemicals Have Proven To Injure Frogs

Atrazine an herbicide manufactured by Syngenta® has been banned in Europe but is still widely used in the USA. It affects the endocrine system of frogs (and humans).

Glyphosate is a common agricultural pesticide used in both home gardens and commercial farms. Sold under the brand name RoundUp™ several studies have shown that it leads to critical changes in frog development.

Pyraclostrobin the ingredient in Headline® is a plant fungicide used in agriculture. It has a high mortality rate from direct contact as well as from runoff into waterways.

Organophosphates (OPEs) are found in many agriculture and industrial settings. They are used when making furniture, electronics, and even plastics. They are cheap and easy to use. They also leak into the environment and negatively affect water and air quality.

Why Does Tracking Frogs Matter?

We are losing frogs. Since 1980 over 200 species of frogs have gone extinct. That’s a lot of frogs in only 40 years. According to the USGS frogs are declining at a rate of 3.79% per year.

Over the past forty years, we humans have put a lot of chemicals into the environment. This type of environmental stress is different from natural stressors.

Frogs have been alive for 190 million years with few evolutionary adaptations. They have survived ice ages, changes in the atmosphere, and changes in habitat. Those changes came slowly and allowed the frogs to adapt.

However, adapting to high levels of chemicals in a short amount of time is too much for their systems. As responsible humans, we need to enact changes to protect frogs.

What Is Being Done To Help Frogs?

A variety of studies and programs have been implemented to protect wetlands and the animals who live there. However, much more needs to be done.

The USDA has launched several programs to incentivize farmers and landowners to protect wetlands on their properties. Canada recently announced that it was devoting $25 million to protect its wetlands.

These programs help to establish buffer zones around wetlands and to provide wildlife corridors that allow natural movement among species.

Homeowners can help toads and frogs by providing wildlife habitats and gardening organically.

How Do Scientists Study Frogs As BioIndicators?

Scientists look at frogs in many different ways. Typically as in the case of Judy Helgen a citizen reports strange behaviors or unusual mutations of frogs in a pond or waterway.

Scientists then go to the location to observe and take samples. They may take samples of the water and animals to a lab to make further tests.

If these tests show some evidence of what’s happening the scientists apply for grant monies so that they can set up a study. The study will have a long-range goal of what they hope to accomplish and find out.

These studies help us to learn what types of chemical or other pollutants are getting into the water as well as how it affects the frogs in various life stages.

Sometimes the Department of Natural Resources will collect data to monitor frog and toad populations. Often these are citizen science or bioblitz events that concerned citizens can participate in.

I am excited to be participating this year in the Wisconsin Toad and Frog Survey. I am currently studying frog calls to make proper nighttime identification.

Guest Author, Ame Vanorio, is an environmental educator and the founder of Fox Run Environmental Education Center.