I was surprised no one has mentioned the dry ice method. It's what they use when harvesting the feathers and want to avoid blood. I have done it 4 times in my 10 years of chicken ownership and very humane. You can google it. I use coffee can large circular platform and 20 gallon rubbermaid...
Doubt fox...they usually eat their prey or take to their young. Possible domestic dog although you would have likely heard that so I guess skunk..night, didnt eat but the buried under leaves???
