Mountain foxes should be really good yet muskrat. The one you seen has probably been living on chocolate chip cookies and sndwiches for several years. When i last worked for an oil company on the coast it was common to see as many as 15 foxes in the yard.

If you have lots of snow then animals should be following walking trails pretty good? I would try a blind trap bedded in the snow on a well used walking trail. Couple skinny willows will help tell the fox where to step. No bait, no lure. Another set that works well for fox is a small cubby style set. Not a giant walk in cubby, just a lure/bait wired to a suitable tree/willow eye level with the fox with a minimum of blocking sticks. Just enough to make an obvious approach. Use whatever is growing in that spot so the few blocking sticks dont look out of place. It should look pretty much like a natural little clump of bushes. The main thing is to set your trap about the distance from a foxes nose to his shoulder so when it either tries to sniff the lure or bite at the bait Its feet should be right where they need to be. The second set i described is the one i caught 54 foxes with one year with a 1.5 longspring that i added an extra spring to 1.5 dls only difference was with that lucky spot i wired the bait a little higher (just high enough where the fox had to reach a bit) and made an slightly elevated spot for the trap. Any animal that wants to reach a little higher will use that little shelf especially if its conveniently right where it will help the fox reach higher. Hopefully all that makes some sense or gives you some ideas to try. Fox trapping is where i first started having success so its kind of sentimental even though i havent really set for fox lately. Still think they have one of the nicest furs when prime and well handled.

Edit- i anchor my trap to the same tree as my bait. Low and under snow.

Muskrat,Some years,here,all the fox stay good until end of feb(season end),other years some will be open and loose by late January.
Here is a couple taken last day of season last year.Hard to tell from the pic,but they had good fur and good colour for late fox.Some times they get very pale from fading later in the year.

Out here the fox close end of feburary, but there still prime

Location is key to start off with next keep things simple as for trapping in the winter Ontario winters (I assume your trapping southern ont)are tough to trap in why easier to catch them in November and December