Can you sleep on a bed without a box spring?

Hey y’all I have two ferrets and they like to get inside of my box spring and sleep and play. I had no issue with this but casually said something about it to my dad and he decided to cover the bottom of it with plastic. At first they went under the bed but didn’t try to go into the box spring but today they found a little hole and went back in. I’ve surrounded the outside of the bed with tons of pillows blankets and other items to keep them from getting under there but they can squeeze their little bodies through. My mattress is extremely old and uncomfortable anyways would it just be better to go without the box spring?