One of the legendary guys around here will take a ticking clock and bury it just below the surface at his trap set.....the yotes can hear the ticking underground and it sometimes is too much for their curiousity......that setup has caught him some really smart ones.
Gern is right on this trick......I read about this one (I believe in Fur-Fish-Game Magazine) many years ago. I have never tried it though. I believe it said do not use a real loud ticking clock....battery is better than wind-up of course, and it needs to be in a ziploc bag. No dirt hole, no flat, no scent or urine. Just a natural set.