Why do they grumble when they're tired?

[~Kaz~]

Just wondering if anyone knows why babies grumble when tired? Not crying or squealing, just....grumbling and that kind of groaning noise in the back of their throats. Sounds like a protest to me.

Also, when does the 'typical' (although I know there's no such thing) baby stop grumbling when going off to sleep?

DS has been doing this heap and heaps the past week, i.e. every day sleep and it's starting to do my head in.

[Olive]

kaz millie moans/groans/talks herself to sleep most times now !! she makes this noise in the back of her throat too!! some may do it as a means of unwinding prior to sleep!