there are some smelly planst at home depot for possums. they make em go away. and for cats, just get like a couple sticks and chicken wire the place (:
Consider creating a chicken wire enclosure.
We had the same problem when we tried to grow tomatoes in a rat infested area. A chicken wire enclosure has kept them safe
Cyan pepper keeps most animals out it is organic and good for plants (just don’t touch your eyes!).
But if you want a cage for possums give up they can squeeze cut or climb their way past anything, cyan pepper will upset their noses and keep them out along with cats, dogs, most birds and any other rodent!
Put a nice fence around them.