Raccoons will stick their arms in anything other than hardware cloth and try an pull a duck right through fencing heart breaking to see. Mink / weasels can get through 1” openings. Dogs fox coyote will dig. And then you have hawks owls and other predators that will fly or climb in.
You’ll need to cover the pen in hardware cloth and put a skirt all around the outside to keep out diggers also cover the top securely so nothing can fly in or climb inside.