How do we know that frogs in Minnesota haven't always had some deformities? Maybe what we are seeing now has always been there, but people have never noticed before.
We do not have much data on the history of frog deformities in Minnesota. But one scientist there, Dr. Hoppe, has been working with frogs for 20 years. He reports that in all that time he only found two deformities like the ones in the pictures, but starting last year he found hundreds:

Dr. Hoppe wrote a paper about his observations. It is hard to read, but you can look at it if you want more information:
| KEYWORDS | past deformities, limp deformities |
| SUBMITTER | Julie Froehlig |