BullGo to the "Windy Watchtower" telerouter. In front of you, you should notice a small cave entrance with some rocks around it. Go inside, up and to the right to find the bull and pick it up.
SheepGo to the "Icicle Arch" telerouter. As you spawn, go down and to the right to find a small cave entrance. Go inside, watch out for the traps, and pick up the sheep. Pick it up to trigger the achievement.