Sorry to hear that about the attack. By your blog post it sounds like you have dogs of your own but they were not alerted during the attack? Seems a little strange that a stray dog could come by and your dogs wouldn't be alerted to its presence. My dogs alert me when something is encroaching weather its a squirrel, hawk, human, owl, possum, etc.. When its a dog they just go nuts.
Could the chunks of rabbit have been pulled through the cage without the door ever opening?
My sympathies, definitely an unpleasant thing to find.
Do you have any pictures of your cages? That's very odd how about the cages being one open/one closed yet both empty... as well as the dogs not reacting...
Do you have coons? I've had them take chickens from tractors which they can only get an arm into; if they can grab the chicken, they can usually pull it over, kill it, and deconstruct it as necessary to remove the parts. They'd also be the predator most likely to successfully open a cage...
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