Ground Hogs (or whistle pigs as they are known here) kind of look like smaller beavers but without the flat tail also looks similar to an extra large Muskrat. Ground squirrels look similar to tree squirrels but live in the ground. And I believe gophers and prarie dogs are the same thing. You can correct me if I am wrong about that last one. I'm sure people will be more then happy to post pics of each. I know you can see ground squirrels at http://www.varmintal.net/avarm.htm there are pictures of a ground hog a few posts back and videos of gopher shooting on www.dogbegone.com