The caribou at Northwest Trek know Dave Meadows’ voice. “Ca-a-ribou!” he calls. “Ca-a-ribou!” As around a dozen or so graceful animals canter up to him, Meadows opens a gate and lets them through. It’s spring – so it’s time for the caribou to go back out to roam, with Meadows as their caribou-whisperer. A keeper for Trek’s Free-Roaming Area, Meadows deals a lot with these gregarious members of the deer family. Rotating with other keepers, he goes out mornings and afternoons to feed them, check on them and lend a hand if any need veterinary care. And every fall, when …