Small portable coop/run, wire on bottom to keep out digging predators?

I'd leave it on since it's portable, and just let them free range as much as possible.

It's hard to move a pen around with birds inside and no bottom

 

I think it's relatively unusual to have wire on the bottom of a chicken tractor. Plus, the chicken wire won't really help prevent predators from getting inside, which is exactly what you're trying to do. Chicken wire is best used for keeping chickens in or out of an area. I would recommend making an apron of wire that extends out from the edges. Here's a thread with pictures and discussions: https://www.backyardchickens.com/forum/viewtopic.php?id=359483 Good luck and

 

I put chicken wire on the bottom of my turkey pen last year for the same reason. I had to take it off when they got too heavy to move though! I never had any problem with predators. If the rest of your pen is secure then...!

 

Pull the wire.

 

I have 2x4 wire on the bottom of mine, the spaces are big enough so they can get to the grass.

 

Don't wire the floor, it defeats the purpose of a tractor. Just skirt around the outside by attaching wire to the run base and letting it lay on the ground. When you move just lift the skirts and hook them to the run, move the tractor, and lay the skirts back down