As far as anyone can tell, the patterns in the songs have no meaning at all. They are just abstract patterns. In any case, it is tempting to analyze this phenomenon by reference to the human phenomenon of fashion. Some such behaviors nevertheless seem to have a complex, quasi-grammatical structure. The best-studied case is mouse grooming .
Mice use their forepaws to spread secretions from oil glands near their eyes.
They do this via a rapid series of motions, which may be forehand or backhand, up or down, from the midline to the side or vice versa, etc. The particular order of such gestures has no functional consequence, as long as there are enough of each type to spread the secretions around. Genetically identical mice use identical sequence patterns. Thus this is a case where a grammar-like organization of behavior is found, though there seems to be no communicative significance. Size of the repertoire It is generally said that individual animals may have a repertoire of up to about 40 different displays.