Tigerlily, with cats I actually started working with Zeke at Petsmart. We would get as far away from the adoption center as possible while still being able to see the cats there. Armed with a squeaky tennis ball(he has an obsession with squeakers, although he doesn't typically play with squeaky toys, and an obsession with tennis balls--noise distraction combined with the love of his life), I would work on recalls and heeling here. If I thought I was fixing to lose him, I'd squeak squeak squeak the tennis ball and become really exciting. When I could heel a certain amount of time and have recalls without him paying any mind to the cats, we'd move a little closer and work some more. At times he would have to heel straight towards the adoption center without looking at the cats, but we wouldn't get so close that I lost him. (By the way, "losing him" was him tensing up and locking his eyes on the cats--he had an unbreakable eye-lock on cats. I could be dragging him away and it was like he was in a trance until we got completely out of site and then it was like he would wake up.) I also did recalls away from the cats, again starting out where he could handle it and it wasn't hard. Eventually we got to where we could heel right past the adoption center, and all around in front of the adoption center. I can't have him sit right in front of the adoption center and call him away just yet; it's a lot of cats instead of just one and if he sits there for very long he does go back into his trance. With just my one cat at home, I can call him away pretty easily.
So, all you need is to get some squirrels, skunks, rabbits, and geese and do the same thing.
Lol. Maybe if you could get a 50 foot leash, or even a 100 foot. No, you don't have to buy one. I bought 100 feet of rope at Tractor Supply Co(any farm supply store should have a pretty good selection of rope) and a clip, and made a leash out of it. I made a handle on one end and put the clip on the other and it's pretty close to 100 feet long. I got it for Zeke's off-leash training and for Deuce, the English Setter I worked with. 50 feet wasn't enough for some of the stuff I was working on.
Anyway, that way you could work on his recall and still be able to keep him from going after a skunk if he decided that was more exciting.
I don't know if that would work for you or not; you have trees and stuff......I live in flatlands with not a whole lot of trees; if the dog takes off they are tearing across a field, lol. Not really anything to get tangled around or caught up in.
Sorry, I'm not much help here. :/