Wow, people talking about ferrets on a horse forum .
I use to have ferrets a LONG time ago and yes, we had them to take care of rodents in the barn, chicken coop, hay shed, etc......
If you are thinking of getting any there are a few things you should know.
The domestic ferret is not going to become feral. They'll die if left in the woods on their own.
If you have a non spayed female you must breed her when she comes into heat. She might survive the first heat without breeding but the odds of her surviving any after that are not good. So if you're not planning on breeding then you'll need to spay in order for her to survive.
Ferrets are born predators. The domestic cat (feral or otherwise) can compete with the ferret for lethal determination.
They must have a meat diet. If we weren't hunting them we use to feed them strips of pork liver, but any good meat protein can do the job.
If you're hunting them (e.g. Cleaning the rats out of the hay, etc...) don't let them have a dead rat until they've finished clearing them out. They'll stop to eat and not hunt. If you're knocking the rats in the head as they race out (and they'll "break a leg" to get away form the ferrets) make sure you're hitting a rat (don't smack the first head that shows itself...it could be a ferret).
If we let them play around in the chicken coop (with the chickens out) and in the barn, hay, etc.... it did cut down on the pests coming back so their scent apparently did keep the undesirables from returning.
After we killed our last cat (it had taken eating my grandmother bantams which was a death sentence ) we never got another one. They never did the job as well as the ferrets. But then how is a cat going to compete with a predator that can go anyplace the rat can go. There's no place for them to escape from a ferret.
I could go to a neighbors and turn a pair loose in the corn crib. In a minute or two there would be rodents coming out from everywhere . Some folks were amazed at the number of rodents they had. They thought their cats were taking care of it, because they weren't seeing many, but cats can't visit the pest where they live. They can't work their way into the small little space between the bales or through the corn like ferret can.
The females tend to make the best hunters. Plus they're smaller so they can get into tighter places.
Have no idea about using just the scent. We had the real thing and I can attest to how well they worked.