im aware that they wouldent catch many rabbits it open ground as they are just to short lol,but when you say marking u mean they get the sent of rabbit and you send in the ferret or start diggin ye?and if ferret was down the hole would the jack manage to catch it when it bolts from hole obviously if it sprinted would be slim chance,and when you say bushing through brambles you mean they will basicly chase them out of the bush or make you aware if they find a hole ye?