I put a piece of cardboard in the whelping box. Everyone had to go check it out, walk on it,and yes, since it was new, someone had to pee on it. Bt after that it was a fun 5-10 minutes watching the four who werent napping come at the cardboard at top speed (not very fast yet) and start across then SLIDE the rest of the way. They kept going back and forth across it. As one stopped in the middle for a nap he got piled on by one or two others trying to get across. Too funny!