Boars are always bigger. Often times you can see the scrotum on a boar. Generally, however, look for a bear which has ears that appear small relative to his head size. The ears will be far apart, often appearing to be on the sides of the head. Large, thick neck, belly that sags, knees that appear to be bow-legged from his weight, and a walk of total confidence are all signs that you are looking at a mature boar. If there is a barrel at the bait site, and his back comes to the top of the barrel (55 gallon) when he is on all fours, that is a big bear.