I would have to say any yearling that has not seen a hunting season! I don't look at a 1.5 year old as a yearling, but as a 1.5 year old! These 1.5 year olds have been thru a hunting season as well a winter. Maybe even shot at Bow and Gun. A yearling has not. Which makes them more of an easier target. A yearling may know danger before its 1st hunting season but not LIFE threatning as in being shot at or grazed by an arrow or bullet. JMO