I live in Texas and earlier today I came home to find one of my medium sized black hens out in the pasture with the horse and it head had been ripped off and the neck was bare but the bones and everything else was intact laying on its back. A few weeks ago we had a raccoon, cat, and skunk. hanging around but haven't seen them in a while....just hard to take seeing it happen to one of my babies....no matter how old they are they are like my kids...
Well, at my parents ranch that same thing happened. They call whatever animal did that a "Lechusa" or Lechuca". I think a "Luchusa" is the spanish word for "owl".
I have had a raccoon and a skunk but they never hurt the hens, they just ate their food. The cats also never bothered the hens. I have heard about owls and other birds of prey doing this, leaving the heads.