East Bison Flats Trail is a 6 mile out and back trail located near Custer, SD and is rated as moderate. The trail is primarily used for hiking and trail running and is accessible from April until October.
I got there a little later than intended and missed hearing the elk bugal much but I did see them on the trail. There were also deer, antelope, coyote, bison and prairie dogs. Signs for the trail at the parking area would have been nice. I nearly missed the small print sign to turn off the 2 track onto the trail. it looked like game used it more than people. Runkeeper said it was 7.6 from where I parked.
This trail is located in Wind Cave National Park. I have run the trail (when I worked at Wind Cave). I believe it is open all year, rather than just April to October. The date I entered is just an estimate.