Mammals have hair on at least part of their body and the females produce milk to nourish the young.
In Illinois there are 70 species known to have recently inhabited Illinois including 5 endangered and 3 threatened species. This includes several species that don’t currently have breeding populations in Illinois, such as Black Bear, Cougar, Gray Wolf, Elk, Fisher, Marten, White-tailed Jackrabbit, Porcupine, and Armadillo.
Endangered
Gray/Timber Wolf (Canis lupus)
Rafinesque’s Big-eared Bat (Corynorhinus rafinesquii)
Southeastern Myotis (Myotis austroriparius)
Gray Bat (Myotis grisescens)
Indiana Bat (Myotis sodalis)
Threatened
Eastern Small-footed Bat (Myotis leibii)
Northern Long-eared Bat (Myotis septentrionalis)
Franklin’s Ground Squirrel (Poliocitellus franklinii)
Silver-haired Bat 
White-tailed Deer 
Eastern Cottontail 
Least Shrew
Groundhog 
Eastern Gray Squirrel 
White-footed Mouse 
Muskrat
