We had the same thing; half eaten chickens buried in the coop. Turned out to be a Fisher which a a member of the weasel family. He must of got in via the roof through the ventilation window. I thought it was high enough not to worry about. We put a mesh wire over the window and will try again...
Sorry to hear, we tried to train our dogs to leave hens alone, all they got out of it was they had to wait for us not to be around before going after the hens. We just keep the hens in their pen by clipping their wings and placing rocks along the bottom of their pen to discourage tunneling.
Thanks for the tip, I will have to keep an eye out on how he acts to the girls. He seems friendly enough; he had less than 12 hens at his last home and is over two years old.
This is my first year raising chickens. The coop was not weather proof for our winter, we had to use a heat lamp to get them through the worse of the cold -30c and colder with the wind chill. We have a new house on order that will be insulated. We are waiting for the weather to warm up enough to...