Mammals are much more difficult to see than birds because of their nocturnal habits and the dense habitats they choose. However, an interested person may see gray and fox squirrels in the woodlands along the loess bluffs, while in the evening and at night he may observe whitetail deer, raccoons, opossums, and coyotes along the roads, and bats hawking for insects or drinking from ponds and streams. One of the best ways to detect the presence of mammals is to look for their tracks in snow, dust, or mud. The drama of their lives may be read in these - how they raise their young, catch their food, and in turn may be caught for food. Signs of beaver and muskrat are easily found along creeks and drains.
Field mice leave narrow winding runs under thick vegetation.
Smaller mounds and linear ridges indicate the presence of moles. Although quiet and usually inconspicuous, mammals are important in the ecology of the refuge. Herbivores such as mice and rabbits convert plant food energy into animal protein which then becomes available to predators - coyotes, mink, hawks, and owls. Larger mammals including foxes, coyotes, raccoons, and opossums often play the role of scavenger as well as that of predator. The following 34 mammals have been observed on the refuge since 1935 by refuge personnel and by mammalogists from educational institutions.