Wild polecats can and do add spark into ferrets from working strains but breeding the right animals isn’t easy, and it takes time.
Pure polecat blood needs to be ‘watered down’ through carefully considered crossings.
I added some “spark” into my ferret strain some years ago but found that the kits from the first cross were hard to handle; many resented being picked up and were quick to show their displeasure.
The early ‘nipping stage’ was bad enough but it quickly gave way to all out full-blooded biting!
I tried to work this litter but got very mixed results, some were very good at finding rabbits but they didn’t like being picked up and would skulk off back into the burrow once it had been cleared.
I then diluted the polecat blood once again by mating with a ‘normal’ ferret and the resulting litter turned out to be very handy workers with a lot more stamina and strength.
The breeding seemed to give my strain the spark they lacked and it produced a superb ferret called Carlsberg (probably the best ferret in the world!) Carlsberg would graft all day and I could rely on him to empty any and every burrow I showed him.
By all means go for a bit of polecat if you think your ferrets need it, but expect a bit of wastage along the way.