Dave has set barbed wire fences with baited with roadkill to attract the wolves and other predators of woodland caribou. When the wolf jumps over the fence, the barbs catch tufts of its hair. Dave collects these bits of hair and they are analyzed for DNA. This gives a much more accurate picture of wolf populations in the area, which is much higher than previously thought. He's found there are lots of coyotes, too, that are invading the region, probably attracted by the high numbers of deer.