Since you have two? Try to track/follow/locate the den. Clean up the whole thing by May and you should be good. Howling around midnight should help you locate the den. Get a response a couple of times in the same general area will get you close.

Found a couple of pair the other day and, in the snow, you could see where a male was chasing a deer. Went for at 3/4 mile before he gave up. Deer to healthy for him to catch on a straight run. (I say 'him' because his track was larger than the second one with 'him', and, she really didn't do any outright pursuing of the deer.)