Thanks everyone. About 12:30am last night he found the warm side hide -- I came out to check on him and about three inches of tail were sticking out of the hide. This morning he was totally inside and his nose just a half inch from the opening. Now he seems to be very happy. I am raising the temp from 85 to 88 on the warm side. I am also turning on the lamp. It won't help at night but the ambient temp in our apt. dropped to 77 last night. At least he won't freeze today.