Frequently asked questions about deformed frogs

Leopard frog with an extra hind leg 1. When did this first start?
The MPCA was first involved in investigating abnormal frogs reported from the Granite Falls area in 1993. Work in the area in 1994 turned up no abnormal animals, but provided basic information. In August of 1995, students from the New Country School in Le Sueur, Minnesota, found large numbers of deformed frogs in a wetland they were studying near Henderson, Minnesota. Before the end of that season, reports of similar frogs occurred elsewhere in the Minnesota River Valley.

2. Do we know what is causing it?
Not yet. According to the Minnesota Pollution Control Agency and the National Institute of Environmental Health Sciences, recent test results indicate that something in the water from research sites is causing the abnormalities. The causative agent itself is still unknown. Studies are still being conducted to determine if it is a chemical, parasite, ultraviolet radiation, or additional factors.

3. Where is it coming from?
Since the agent causing the malformations is unknown, the source is also a mystery. Does it come from the air or from the land? Is it "natural" or man-made? We don't know.

4. Where are the frogs being found?
Reports of malformed amphibians have been reported in 35 states in the U.S. and 3 provinces in Canada since 1996. In Minnesota, nearly three-quarters of our 87 counties have reported malformed frogs since 1996. 

5. Does Minnesota have more deformed frogs than other states?
Minnesota has had probably more reports of malformed frogs than other states. This may be due to increased public awareness of the issue and not necessarily because our numbers of malformed frogs are higher. However, biologists with nearly 40 years of experience in surveying frog populations here have never seen abnormalities to the extent they are present in the state now. This appears to be a recent phenomenon in Minnesota.

6. What kinds of deformities do the frogs have?
Some frogs have missing eyes, but most problems are associated with the limbs, especially the hind legs. These deformities typically include missing limbs, extra limbs, partial limbs, limbs that are bent and contorted, or limbs that have little muscle, or that have branched at various points along the limb. Problems in the digestive, urinary and reproductive organs have also been found in frogs with external deformities.

7. Can the deformed frogs still function?
Many of the deformed frogs can still function; however their ability to eat, move, migrate, and avoid predators can be slightly or greatly hindered depending upon the severity of the malformation(s). Few frogs live into the second year -- it appears they don't survive the winter.

8. What kinds of frogs in Minnesota have been found to be malformed?
In Minnesota, abnormalities have been documented mostly in the northern leopard frog, and to a lesser extent in wood frogs, green frogs, mink frogs, gray treefrogs, spring peepers and American toads.

9. Have other of kinds of animals in North America been found to be malformed?
We have also heard of some malformations in bullfrogs, gray treefrogs, Pacific treefrogs, American toads, long-toed salamanders, tiger salamanders, and spotted salamanders. But, mostly it is frogs.

10. What are the types of places where they are found?
Malformed frogs have typically been found in wetlands or ponds, depending upon the species and the type of environment for which they are best suited. They have also been found in both urban (in town) and rural (in the country) areas of the state. There doesn't appear to be any geographic pattern in the findings at this time.

11. Is the water the frogs live in unsafe for human use?
Recent studies showed that well water from several sites in Minnesota can produce frog deformities. This has caused some people to wonder if their drinking water is safe. Standard drinking-water tests were run on the water, and nothing was found. Tests are being run now to identify what in the water causes frog deformities, but it may be some time before we know what it is, or whether it can affect humans. Until more is known, there is no scientific evidence that the water is unsafe for humans.

12. What is MPCA doing about it?
From 1998 to 2000, the Minnesota Governor and Legislature gave the MPCA special funding to study the frogs. The MPCA worked primarily with researchers and scientists from the University of Minnesota, the National Institute of Environmental Health Sciences, the US Geological Survey and also with the National Wildlife Health Center and the U.S. Environmental Protection to investigate the problem. These partners provided extensive chemical and toxicological analysis of the water and sediments, and characterized the internal abnormalities and analyzed parasites and microorganisms. As of July 1, 2001, funding was eliminated for the MPCA to study the frogs.

13. Where can I find more information?

  • Contact:
    Ralph Pribble, MPCA Public Information Office
    651-757-2657 or (800) 657-3864.