Spring hunting fever...he'll calm down.
I have an unneutered male bassett, and I have to keep him tied in a pen after a stray taught him to dig. I hate it, but being a bassett he would (and has) got on a scent and looked up 5 miles later wondering where he is. He like most of his breed is not quite astute enough to realize that if he followed the same scent back, he'd get home. Gotta love a bassett.
Do something temporary, like tying a concrete block to his lead, until the season starts to fade. Hunting dogs get that way in the spring, it's actually a sign of a good dog.