It's not like Deer are going to populate it. So you're just talking about small animals like Rabbits, Squirrels, Cats and at worst, Raccoon.
They're fine in there. If, by some fluke chance, they're on the coaster track when the coaster is going over it, they'll simply get flattened and know one will no any different.
The only issue on a roller coaster is a bird. Just ask Fabio.