Gravity as the sole navigational aid to the newborn quokka.

Abstract

ALTHOUGH there is general agreement on the sequence of events at birth for several marsupial species1, it is still not known how the newborn joey navigates on its journey from the mother's cloaca to her pouch. Frith and Calaby2 have postulated that, at birth, the red kangaroo (Megaleia rufa) “… has large nostrils and presumably a well developed sense of smell which probably plays a major part in its location of the pouch”. On the other hand, Hartman3 has suggested that the newborn opossum (Didelphis virginiand) was “negatively geotropic” though he has now modified this view considerably4, as histological studies have revealed that the vestibular apparatus of the newborn animal is undirTerentiated and therefore nonfunctional5,6. To investigate whether one of these mechanisms2,4 could account for the behaviour of the newborn quokka (Setonix brachyurus) we have observed parturition in this macropodid marsupial.