Many grey hounds' lower jaw trembles making it chatter when they are excited. This is quite a normal phenomenon and nothing serious. This may happen when they see food, see their favorite person, or when they are poised for some activity such as playing or walking. Again the owners should know that chattering of jaws is not due to cold but just a way for them to show that they are excited.
They may do this when they are extremely happy too. Some other ways that they show their excitement or happiness is nibbling on someone's fingers or snapping in the air. Nibbling may be playful but may be enough to leave bruises on the person's hands so one should be careful. Although snapping and chattering may appear as aggressive behavior to an individual who is not familiar with greyhound behavior, but are quite harmless expressions and not signs of anger.
They may do this when they are extremely happy too. Some other ways that they show their excitement or happiness is nibbling on someone's fingers or snapping in the air. Nibbling may be playful but may be enough to leave bruises on the person's hands so one should be careful. Although snapping and chattering may appear as aggressive behavior to an individual who is not familiar with greyhound behavior, but are quite harmless expressions and not signs of anger.