Here are two good links that will give you a ton of information about animals in Wisconsin.
1. Animals, Plants, and Natural Communities - This link is pretty scientific at first, but once you find the list of common names (rather than than the scientific names - even I can't read those) it gets easier. There are pictures and short descriptions, including what animals are endangered.
2. Eek! Critter Corner - This site is just for kids. It includes many animals in Wisconsin, organized by type of animal, and includes endangered species. There are pictures, descriptions, and fun facts about a lot of different animals. (I just read about the firefly!)