A review of the nutrition of Australian peramelid marsupials

Abstract

European settlement has had a dramatic impact on the distribution and abundance of peramelid (bandicoot and bilby) marsupials. Predation and competition from introduced species and altered habitat have been implicated in their decline or extinction. Bandicoots and bilbies inhabit a broad range of habitats in Australia. Research on the distribution, morphology, gastrointestinal histology, lactation, metabolism and nutritional physiology of extant peramelid species has increased in the last few decades. This paper provides a review that encompasses recent nutritional-based research. Peramelid research is mostly limited to only three species – Isoodon macrourus, Perameles nasuta and Macrotis lagotis – which prevents effective comparisons between species. Peramelids are broadly classified as omnivores and possess relatively uncomplicated gastrointestinal tracts. The caecum is the region of greatest diversity among species. The relatively large caecum of Chaeropus ecaudatus supports the theory that this species may have been the only herbivorous peramelid. The caecum of M. lagotis is less pronounced than other species and is continuous with the proximal colon. M. lagotis also has a longer total colon length, which aids water conservation to ensure survival in an arid environment. Temperate-zone species such as I. macrourus, I. obesulus and P. nasuta are more similar to each other with respect to gastrointestinal morphology than either C. ecaudatus or M. lagotis. Additional research on the morphometrics of the gastrointestinal tracts of P. gunnii, P. bougainville, P. eremiana, M. leucura and I. auratus would enable further comparisons to determine whether differences are a result of geographic distribution, habitat preference or variation between genera and/or individual species. Currently, histological information of the gastrointestinal tract is limited to the small intestine of P. nasuta and I. macrourus. The histology of the small intestine of the weaned juvenile I. macrourus more closely resembles that of P. nasuta pouch young than P. nasuta adults. The younger bandicoots possessed villi whereas in the adult P. nasuta and I. macrourus villi were arranged in a zig-zag formation. The reason for the zig-zag formation of the villi and the function it may serve remains unclear. Detailed nutritional research on captive M. lagotis, I. macrourus and P. nasuta indicate that the two temperate-zone species – I. macrourus and P. nasuta – are more similar to each other than to the arid-dwelling M. lagotis. Detailed nutritional studies are required on all species, both free-living and captive. Experimental diets do not always accurately reflect a natural diet, which means that results from captive studies may not reflect the situation for free-living animals. The hindgut of peramelids is the main region for retention of digesta, and presumably where microbial digestion occurs. However, no studies have been undertaken to examine the microflora of the gastrointestinal tract of bandicoots or the bilby. As captive husbandry is an important tool in conservation management, it should also improve their successful maintenance in captivity by the provision of diets that better meet their nutritional requirements.