DIGESTIVE PERFORMANCE AND SELECTIVE DIGESTA RETENTION IN THE LONG-NOSED BANDICOOT, PERAMELES NASUTA, A SMALL OMNIVOROUS MARSUPIAL

Bandicoots are opportunistic omnivores that feed on invertebrates, fun gi and both epigeal and hypogeal plant parts. We examined the performa nce of the digestive tract of the long-nosed bandicoot (Perameles nasu ta) in terms of intake and total digestibility, patterns of excretion of inert digesta markers, and likely sites of digesta retention, on tw o diets designed to mimic part of their natural plant and insect diets . On the insect diet (mealworm larvae), bandicoots virtually maintaine d body mass at a digestible energy intake of 511 kJ . kg(-0.75) . day( -1) and were in strongly positive nitrogen balance. In contrast, on th e plant diet (shredded sweet potato), bandicoots ate only one-third as much digestible energy, lost 7% body mass, and were in negative nitro gen balance. Mean retention times of two particle markers on the plant diet (27.5 and 27.0 h) were more than double those on the insect diet (12.4 and 11.2 h), and on both diets the mean retention time of the f luid digesta marker was greater than those of the particle markers, in dicating consistent selective retention of fluid digesta in the gut. I t was seen radiographically than in mealworm-fed bandicoots major site s of digesta retention were the distal colon and rectum, whereas in th e sweet potato-fed animals the caecum and proximal colon were principa l sites. It was concluded that retention of plant material in the caec um and proximal colon (the main sites of microbial digestion) and the preferential retention of fluid digesta (together with bacteria and sm all feed particles) in the caecum were important factors in the abilit y of bandicoots to switch between insect and plant foods, depending on relative availabilities, and thus to exploit nutritionally unpredicta ble environments.