Chirping Gerbil Issue
My gerbil has been chirping a lot recently. He sits in his hut/house and chirps (deeper chirp, sounds like its coming from the back of the throat). He was even doing this when I held him. I've owned the gerbils for 2+ years, and they've never done this before. I'm wondering if this is because of some sort of pain or something else serious. He stops when he is sleeping and eating
Notes: His brother died a week or so ago. I used to have 3, now 2. So he's not lonely. Could he be mourning?