you need to first get the unidentified fur and identify it. Once you've done that, go back to purto rico and the dude will say he's off to trap the chupacabra. Then herd three spotted goats into the half circle of rocks, which is the middle star. Do it with the jeep. Then get out there and do what the guy says to, which is to hide behind the rocks. after the chupacabra comes push the crate onto the truck. It will burst out, but leave behind a tooth.