grunting rat

Question
Hello there! I have two male rats who are a couple of months old, and I'm curious. One of them makes a sort of grunting noise, not all the time though. It's not a pained sound, and I've been keeping my eye on him and he has no runny eyes or nose, coat is clean and shiny, he eats and drinks well, plays with his brother and sleeps an average amount. I've also listened to his breathing and he makes no noise at all. I usually notice this noise at night or when I give him food. Most of what I've read says that rats only make noise when they are alarmed or afraid or fighting with other rats, but often when he makes his grunting noise his brother is nowhere near! So I'm wondering if it is possible that I just have a chatty rat? I will definitely take him to the vet if it seems like there is something wrong with him but he seems to be perfectly happy!
Thanks in advance :)

Answer
 Well I've heard rats squeak, chirp, hiss, and huff, but I've never heard one grunt before!  If he seems otherwise fine, his breathing sounds are normal, he doesn't appear to be in any pain, and it isn't while he is fighting, I wouldn't worry too much about it, but it certainly is a bit weird.

The huffing sound is the only thing close to a grunt I have heard, and it is usually made by a really mad rat either towards a human or another rat.  Usually it is accompanied by other aggressive signs such as puffing out the fur and biting, so I don't think this is the case here.  I'd love to see a video or hear a recording of it as I am curious to find out what it may be as well!

He is probably perfectly fine, but just keep an eye out for any other signs of illness or change in behaviour and also note if he starts making the sound more often.  If there are any such changes it would probably be a good idea to take him to a vet, otherwise he is most likely happy and healthy.

Good luck with your rats!