I think chinchillas, like human kids, take a lto of their behavioral cues from their parents. I find that my most vocal kits have very responsive, vocal parents. I have females that chirp to thier babies constantly, and the babies always grow up to be very vocal adults, and vocal parents. I also have one female who almost never makes noise with her babies and tends to be less responsive to them, and they, in turn, are very quiet babies, and only make noise when they are mad or scared.