Weird sound at night?

[rawrrr]

I've been trying to introduce two chinchillas using the side-by-side cages method, and during the day there have been no major problems - no barking, no attempts at aggression through the cage, etc. The last two nights, however, I've been hearing a weird, new sound. It's kind of a shrill, squeaky noise. Sounds like "Upset and annoyed", the last one listed on http://www.cheekychinchillas.com/chinsounds.html. Before I can get up to check on them, however, I hear the normal chattering noises that one of them makes, and when I do see them they're fine and playing by themselves.

Should I be worried? Should I separate the cages further? (They're 6-7 inches apart right now, to ensure that no tails can be grabbed).

 

[Strevale]

They might just be playing and one did something the other didn't like so he got warned. It's not something to worry about unless they are trying to fight.