Where Houdini is blind, he doesn't really have much of a circadian rhythm anymore. He's always out running around at night. I can go in a 4 in the morning and he's on the move. Downside is he's right next to Sithis' cage, and after only a week or two Sithis has started coming out at night to watch Houdini and sleeping during the day.
It's kind of cute.