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 nonfunctional^5,6. To investigate whether one of these mechanisms^2,4 could account for the behaviour of the newborn quokka (Setonix brachyurus) we have observed parturition in this macropodid marsupial.