>Is chuckling or dooking known to be anything but a sound expressing
>happiness, a desire to play, joy, etc.?

I would take a gander that she is probably Deaf. Have you done anything
to check that out yet? Squeek a toy or something behind her head, see
if she reacts. Likely she is deaf and has never heard a dook so doesnt
know to make them, and its just her way of making a 'noise' that she
registeres, with a strong vibration in her throat.

[Posted in FML 5895]