Everyone is wrong. It is a Virginia Opossum. Just kidding unless you are from south of US border with other similar opossum species. Those little dudes and dudets are a pain in the butt. Big ones are fairly easy to keep out, but the young ones, man they are as bad as snakes when it comes to getting into pens and eating eggs. At night half grown and better opossums can be very hard on roosting adults, especially hens roosting low on eggs or with chicks.
I have taken to culling them as they can also put a dent in your feed.