A few people find themselfs in this position i can only use a terrier on my ferreting permissions. ive seen good russells, borders and lakie types mark very well. i use a bedlington very good marking dog, great temperament, lives in.On the stubborn side to train as a young dog but he is obedient and works close.i dont think you could go wrong with any of the types mentioned as long as you put the work in early obedience, socialising, breaking to ferrets stock etc. good luck with your choice.