I've always made sure to leave enough dry cat food out back, along with keeping the water bowls filled, and I hear the possum every night as he cleans them out and gets a drink. He is a great big male and could probably rip chicken wire off the pen if he wanted to, but he's never bothered the chickens. And I've found possums in the chicken house years ago before I started the cat food thing. Once I heard about how they are clean, well groomed animals who eat ticks, they became my nocturnal visitor of choice.. They are clumsy, but not destructive like raccoons. I read somewhere that their body temperature is too low for ticks to actually be attracted to them. Just sitting outside the back door where I feed the cats, I got a few ticks for about a month when my cats had kittens...I think the mamas chased him off...but now he's back and I'm not getting ticks any more.
Possums are sort of slobbery, so I switch all the food and water pans every morning and rinse out the used ones I bring in.
One of my sisters used to feed a whole clan of raccoons every night and they never once bothered her chickens and rabbits or her caged rescue cats.
