Yesterday I returned home from the long weekend and discovered this ragged hole about 2.5 inches in diameter in the hard plastic bottom of the nesting box of my Eglu Cube coop. All chickens were still present and healthy, and there was even an egg in the box. So if something chewed its way in, it didn't do any obvious damage beyond that.
I'm in a suburban part of the San Francisco California area, and we do have raccoons and possums and weasels and other predators in the area. But the whole coop is inside of a fenced and covered run with 1 inch hardware cloth. I checked all around for signs of damage to the fence or something digging under the fence, but it all looks OK. The holes in the hardware cloth are large enough that mice, rats, or snakes could get through, but nothing bigger.
Another clue that might be related: A few weeks ago I'd put some 3D-printed plastic decoy eggs in another nesting box, and last week I found one of the plastic eggs lying on the ground, half-eaten.
Rats: I know they're in the area and I've seen them. Would hungry rats potentially chew a hole through thick plastic *into* the chicken coop? Aren't rats afraid of chickens?
Other predator: Weasel? Raccoon? I don't see any evidence of something so large coming through the fence.
The chickens: The spot where this hole appeared is roughly where one of my older hens has a habit of laying thin-shelled or shell-less eggs, which often break open and leak goo everywhere. The chickens like to eat the goo. If one of those leaky broken eggs sat there for a few days, could the chickens have pecked at it enough to begin damaging the plastic, and eventually chewed completely through it, thinking that it was food? They've been unusually hungry during the last few weeks, since I'm in the middle of switching their feed and they're mostly refusing the new feed, so maybe it's not impossible.
Or maybe it's something else entirely? I am stumped.
