Nutrition of marsupial herbivores
I. D. HUME
School of Biological Sciences, University of Sydney, New South Wales 2006, Australia
Mammalian herbivores can be divided into two groups on the basis of the principal site of microbial fermentation. Fore-gut fermenters have an expanded and differentiated fore-stomach. Eutherian fore-gut fermenters include sloths, colobid monkeys, hippos, peccaries, camelids and ruminants. Marsupial fore-gut fermenters include the kangaroos, wallabies and rat-kangaroos.
Hind-gut fermenters have an expanded caecum, proximal colon, or both. They can be divided into caecum fermenters and colon fermenters (Hume & Warner, 1980). In colon fermenters the principal site of microbial fermentation is the proximal colon. A caecum may or may not be present. When it is present, as in the horse, it seems to function largely as a simple extension of the proximal colon. In the only marsupial colon fermenters, the wombats, the caecum is represented by a small vermiform appendix.
In caecum fermenters microbial fermentation is more-or-less confined to an enlarged caecum. Eutherian caecum fermenters include rodents (e.g., beaver, porcupine, guinea pig) and lagomorphs (rabbit, hare, pika). Marsupial caecum fermenters include several arboreal species that specialize on Eucalyptus foliage as food, such as the brushtail possum (Trichosurus vulpecula), ringtail possum (Pseudocheirus peregrinus) and greater glider (Peruuroides volans). The koala (Phascolarctos cinereus), another Eucalyptus specialist, exhibits features of both caecum fermentation and colon fermentation.
The present paper reviews research on digestive function and nutrient requirements of marsupial herbivores, based on the general outline of herbivore digestive adaptions outlined previously.