Kids first noticed the problem. On a field trip to a pond one day in 1995, Minnesota middle-school students discovered something really weird: one-legged frogs, stumpy-legged frogs, frogs with extra legs.
The kids were spooked.
More amphibian deformities turned up, not just in Minnesota but in other spots in the United States and around the world. A few scientists had known amphibians were in trouble, but the students' discovery called global attention to a problem that turned out to be more serious than previously thought: the mystery of the malformed frogs.
Why are we worried?
We've known for a while that some frogs are disappearing, because new homes, stores and roads are replacing their marshy habitat. But it was a surprise to find deformities--abnormal body parts caused by something that must have happened very early in the frog's development.
Only a poisonous chemical or some other dramatic change in the environment could cause such abnormalities. And if these changes caused strange frogs, people wondered, what were they doing to the whole ecosystem, including humans?
Frogs and other amphibians are very sensitive to pollutants because they are so exposed to their watery environment, as eggs and tadpoles. Scientists regard them as sentinels, sort of an early-warning system for ecological problems.
There's another fear. In the last 10 years, many species of amphibians have either become extinct or are on the verge of disappearing. Deformities could be hastening that process, because they make it tougher for amphibians to get food or escape from predators.
What's going on?
No one is sure of the causes, but many scientists are trying to figure it out. Here are some of the theories.
Parasites: Some flatworms are parasitic, meaning they live off another animal. They can burrow into the developing frogs, causing cysts, which are clumps of tissue that can cause developing limbs to be malformed. This theory implies a "natural cause," meaning that humans are not responsible. But scientists are critical of this idea, because the parasites have only been found in some of the deformed frogs.
Light: Because the protective layer of ozone around the Earth is thinning (probably due to chemicals from air conditioners, pesticides and other sources), more of the most damaging ultraviolet light (UVB) is shining down, possibly causing genetic damage to the frog embryo.
Water: Most scientists think there's something in the water. One strong piece of evidence: Scientists have taken water from places where the most deformed frogs have been found, raised new frogs in it and produced high rates of deformities in them.
So scientists are checking for the presence of fertilizer from lawns and agriculture, and for insecticides and pesticides. Some scientists suspect retinoids, a kind of chemical that tells embryos to grow. Retinoids can cause limb malformations in frogs, experiments show. Methoprene, an insecticide used to kill mosquitoes, was one of the first suspects, because a byproduct of the chemical acts like a retinoid. But methoprene was not being used in some of the freak-frog hot spots, so that theory has also been questioned.
What are scientists and the government doing about this?
The U.S. Fish and Wildlife Service just began a study of frog deformity rates in the nation's wildlife refuges. They kicked off the campaign at the Patuxent Research Refuge in Laurel. Ponds sampled there last summer had higher than normal rates of deformed frogs.
The studies will focus on the possible impact of pesticides, fertilizers and other pollutants. Scientists are going to 43 refuges in 31 states. It's not always easy. In Alaska's Kenai peninsula, wildlife specialists needed to carry guns to make sure the scientists catching frogs were not caught by bears.
The surveyors go to a pond, catch 50 or more frogs and send any possibly deformed ones to a laboratory for X-rays and other tests.
Other scientists are studying the problem in the laboratory. One of them, Carol Meteyer, of the U.S. Geological Survey, feels "a little disappointed we haven't figured it out yet." We would do well, Meteyer says, to heed the advance warning amphibians seem to be sending.
"They may be more sensitive than any other creatures out there," Meteyer says. "If there's a problem with our water, it's likely to hit them first."
FOUND A FROG?
Here's what should you do if you think you've found a deformed frog:
Try to identify the species.
Measure it if you can.
Describe the deformity.
Take a picture and include something for scale, like a quarter (so a professional can establish the real size).
You should then call the North American Reporting Center for Amphibian Malformations (run by the U.S. Geological Survey) at 800-238-9801. Their Web address is www.npwrc.usgs.gov/narcam. They probably will say that you can let the frog go and may ask you to send them your report and pictures.
You can also call the Thousand Friends of Frogs, run by the Center for Global Environmental Education at Hamline University in Minnesota. The phone number is 651-523-2812 or 800-888-2182. Their Web address is cgee.hamline.edu/frogs/.
Also helpful is FROGWATCH, which can be reached through the amphibian monitoring section of the USGS Patuxent Wildlife Research Center Web site. The Web address is www.pwrc.usgs.gov/. All these sites have links to the many other frog resources hopping around the Web.
A RANGE OF PROBLEMS
It's easy to see why people are alarmed by these deformed amphibians. Some of the frogs have extra legs sticking out at weird angles. Some are missing legs or toes. Others have legs webbed to their body with extra skin, or have legs split in two, halfway down. Some have missing eyes. (One seemingly one-eyed frog turned out to have a second eye growing inside its throat.)
As scary as they may seem, malformed frogs and other creatures have been around for years. It's probably normal to have about 1 or 2 percent of frogs deformed, scientists say. But some ponds in Minnesota have had deformity rates of as much as 60 percent. Recently, some U.S. wildlife refuges have had frog deformity rates as high as 17 percent. At the Patuxent wildlife refuge in Laurel, the rate last year on some ponds was about 5 percent.
