If you look at a bears rib cage from the front or rear you would see it is more horizontal shaped than a deer . This is the reason we always kept our treestands rather low to keep the angle of the arrow more flat. Depending on the size of the bear their lungs are a little smaller than an adult deer but I would say their heart is about the same . The last bear I shot I hit right in the middle of the body didn't look like a good hit but he died in 40 yards . The big snuffer hit something good !