I have 2 bonded female chins (mother and daughter) who are caged together that I recently adopted. The previous owner didn't have a house for them to sleep in, they would huddle together in the bottom of their cage. I just upgraded to a FN182 cage, and I gave them a house that both of them can fit in, but noticed that only one of them will sleep in there at a time. The other one will either sleep right outside it, or on a shelf. Is this some sort of defense behavior, or do I need a separate house for each one?