My jack russel is a decent ferreting dog , marks, catches hole hoppers ( great when using long nets on hedges seems to be on them if they run the top of the hedge, real quick through cover), good anticipation of whats going on below ground( can't beat the ears cocked staring at hole stance) she's constantly working real busy dog. she was easy to break to ferrets and stock.
Downsides..... hard mouthed ( the ferrets get the ones she 's caught), not quick enough out of cover ( although she normally puts enough pressure on them to put them back in pretty quick), a bit noisy as a marker snuffli