If a predatory animal is attacking me, a charging animal of any sort, which is what I take you to be saying, i'm going to shoot for the chest.
A predatory animal still has a brain the size of a grapefruit and a body the size of a compact car. The idea of bobbing my croshairs around trying to put that round between his angry red eyes is never going to even enter my mind, I'm going to put my crosshairs into the center of that things chest and fire as soon as I get on target. I can probably get two or three rounds into its chest in less time than I would take to miss his head twice.
The story of old Eddie 'flapjack' von fleming, the african hunter is interesting. He made a head shot at an angry elephant and missed. An elephant's brain is not much larger than a human's, and hidden behind that great big head. The heart is about three times or more larger than the brain, and any shot at the heart is still in the area of other organs and nerve systems, as well as necessary bones.
There just isn't any good reason to attempt a head shot on a predator of any sort. without trying every other possible means first, and even then, it's possible, if not probable, that repeating the same shots several more times would be a more effective thing than to give up after firing two shots at the chest and attempting to shoot the head?
I have sometimes wondered, what if you miss the first two shots? what if you can't tell if you hit on the first two shots? Do you yell at the bad guy and ask him if you got him?