Animals like boar and bear have sloping skulls that may at times deflect even the most powerful bullets unless they hit at just the right angle. It is like skipping a stone off water. If the angle is right lots of stuff will deflect.
How many North American game mammals or birds can you name that don't have a sloping skull? Let's see, they are all sloped or all can be sloped depending on your shooting perspective.
Will Lowman borrowed an image from THR. Actually, I believe he probably borrowed it from Flintknapper's monumental thread there. Be that as it may be, if a person made the shot shown in Lowman's image, it would have been bad had it been on boar, bear, deer, bobcat, coyote, or a person.
Ideally, you want your angle of incidence (impact trajectory) to be as close to perpendicular to the impacted surface as possible if it is on the head.
I have made several shots that impacted just about where the bullet did in Lowman's borrowed image...and the bullets did their job and produced instant kills. Simply put, when making such a frontal shot, you don't shoot when the head is up unless you want to risk a glancing blow.
Just kind of curious because Ive read about 40sw bouncing off a deer's head from point blank range, a 44 mag not penetrating a boars head and then read about a 380 right between the eyes dropping them dead.
Oh, like this video of the .44 mag that "bounces off the head of the little bitty pig several times? What a joke! If you watch closely, you will actually see that the bullet misses the pig numerous times.
http://www.youtube.com/watch?v=rI0l29YGA-c