Evidence for the occurrence of rumination-like behaviour, or merycism, in the koala (Phascolarctos cinereus, Goldfuss)

This paper provides the ®rst account of merycism in koalas (Phascolarctos cinereus), and in doing so, potentially sheds new light on the occurrence and signi®cance of this behaviour in other herbivorous marsupials. Koalas ®tted with acoustically sensitive transmitters, to monitor mastication and ingestive behaviour, were also found to make bouts of rhythmic `mastication-like' noises that were not associated with ingestive feeding events. On average, these bouts consisted of 9.16 `mastications', at an average rate of 1.21 `mastications' per second, and occurred 53.3 times throughout a 24-h period. Furthermore, bouts were usually preceded by, and always followed by, a series of `creaky', guttural noises that were interpreted as regurgitation and re-swallowing, respectively. Merycism may allow koalas to periodically re-masticate gastric digesta, while in a resting position, and thus potentially save energy and increase the extent of food preparation. Consequently, merycism may contribute to the koala's ability to consume a high ®bre, poor