Where is worthwhile wildlife and scenic photography in Wyoming and South Dakota?

In late April, I am taking a two-week of vacation along the I-25 and I-90 corridor from Wyoming east of the Rocky Mountains through South Dakota. Since I usually spend my time in the wilderness, I need ideas for good off-season wildlife viewing, tent camping, and eco-tourism in the Black Hills area. Any good locations for antelope, bears, buffalo, prairie dog towns, moose, and other wildlife that can be found and are accessible during the late winter would be helpful as well as other adventure ideas on primarily a "road" (ugggh) trip. Another possibility would be a detour on Federal 191 to the Tetons, then east. Thanks for the brain-storming!