tbird86; Was it near the base of a cut bank, was it on a flat slope, what did it smell like, did it have a lot of fleas in and around it.
It's on a gentle slope 10-15 yards from the base of a tall terrace - probably as close to what you're calling a cut bank as we have around here (rolling farm hills in NW Iowa).
I didn't notice any smell or fleas, but didn't want to get right up in it & disturb it -- I can view this concealed from about 150 yards.
Female red fox at this time will have a strong musky odor similar to skunk, swift fox not so much but them and prairie dogs will have a ton of fleas in their den holes as do the red fox. Badgers dig rather large holes with dirt thrown back away from them often and not many fleas, rabbits usually have a smaller hole with a dust bath close by. Skunks make small holes like rabbits and swift fox do but you can smell them.
No swift fox or prairie dogs within a couple hundred miles of here. The excavated dirt was thrown back 6' from the opening.