I found this in the nesting box yesterday. I had harvested eggs about 2 hours previously (checking regularly so they don't get too cold). The other boxes were full of eggs, this box just had the one. Not unusual. There was still a great glob of yolk inside, but all the white was gone. Minimal mess in the nesting box. Virtually the whole egg is in tact but kind of crushed a bit. I've never seen this! Someone once mentioned skunks poke holes in eggs. They're fully enclosed in a run and the coop is shut tight. I don't see how a skunk could've gotten in there, eaten just one egg, not bothered the chickens, and got out in that time frame. But maybe? I have no rats in the area. Possum (I've heard, but have never seen one), coon, skunk, mink, the rare otter, cats, squirrels, mice, voles, coyotes, foxes... that's about the sum of the 4 legged 'pests/predators' around here.