I really want to know too! I've only gotten mine 3 weeks ago and he's been doing this for the last week. He almost got out once and just keeps going around looking over everything and pushing at the top. He seems to only do it the few hours during the evening and at night.

I've read that lifting the head is a way to search for food ? Though I am not certain where I've read that.... and they being nocturnal would explain the night escapades.