I tried to edit my previous response but I only have so long to edit. So let's try this again, lol. I had said that I bet it's due to the fact that his owner is not there. They call it separation anxiety. My little girl acts up if my boyfriend doesn't travel with us (she's very close to him). And yes, this happens during the night, as well. She constantly is jumping down from the bed (she sleeps with us at night) and whines at the door. I usually never crate her, but this is the one time I have to. She usually just settles right in and falls fast asleep once in the crate. Is he crate trained? I would give this a shot if he is. The crate is supposed to be their safe and secure place for them, I know it is for Maya. I hope this helps some, hopefully others will chime in and be able to give you better advice. Good luck! And I hope you get some sleep soon.
How long will you be watching him?