Vocal Communication Between the Mother and Young of the Eastern Gray Kangaroo, Macropus-Giganteus, and the Red Kangaroo, M-Rufus (Marsupialia, Macropodidae)

Abstract

The structure, development and function of the isolation call produced by the young of the eastern grey kangaroo, Macropus giganteus, and the red kangaroo, M. rufus were compared. A total of 416 isolation calls from 26 eastern grey kangaroos and 272 isolation calls from 14 red kangaroos in four age classes during pouch life were analysed sonagraphically. Twenty structural parameters were measured from each call. Results showed that the isolation call identifies the caller as a dependent young and potentially transmits a variety of other information including the species of kangaroo, the caller's sex, degree of arousal, individual identity, age and location. The main information processed by the young's mother is likely to be that the young is calling and its location. However, the locational qualities of the call decline as the young becomes more independent, presumably to counteract location by predators. The young of both species produced individually distinct isolation calls but mother-young recognition by auditory cues alone seems unlikely. Habitat differences may have led to divergence in the call structure of the two species. The factors that affect the evolution of this type of call structure are discussed.