Opossums will do that - eat only the head and neck. In my experience of having had a raccoon attack, they make more of a mess (I won't go into the sad details!) But it's because of that, that I always, always, latch my hens in at night. Around here we have fisher cats that can climb and rip netting off of pens, so unless you have a pen perfectly enclosed with chain link fence, a predator can get in. Also, raccoons will reach in and grab what they can. Chickens have terrible night vision and won't see predators coming and can't move out of the way, so if they're roosting outside, next to the fence, they can still be grabbed.