Not having ground or leaves didn't discourage Buddy from trying to bury his nuts. He would shove them between the couch cushions, in the hole chewed in the stool, under the newspaper on the floor, into the broom bristles (he would bury one in them, and another one would pop out), and in the half sock pieces on the floor.
When he saw something unfamiliar, that he wanted to eat usually, even though it wasn't food, he would crawl very slowly up to it, holding his tail completely to one side. I believe it was a total of three times while we had him, we heard him making "chuck chuck chuck... weeeee" noise. The "weeee" noise was high pitched and sounded something like a baby kitten.
Click here to hear a bad quality recording.
A few times we had visitors over and we would show them the squirrel, and he would freak. He always ran away and hid from strangers (anyone but us). He would also become very alert and nervous when he heard strange sounds, such as doors opening and closing. This was also a good sign that he would be ok to release.
Some more notes...