Digestive Strategies of Mammals

Understanding an animal’s nutritional niche is fundamental to a full appreciation of its ecology , and is important for both pest control and species conservation purposes. Carnivores have digestive systems dominated by the small intestine , which can be related to the generally high digestibility of their food. Omnivores have more complex gastrointestinal tracts , with a hindgut caecum in which some microbial fermentation takes place , and they have longer mean retention times (MRTs) of digesta. The longest MRTs are found in herbivores , in which digesta are retained and fermented by dense microbial populations in one or more regions of relative stasis. However , not all herbivores have digestive systems that maximise fibre digestibility ; only ruminants , camelids and very large hindgut fermenters (rhinos , elephants) achieve this. Instead , many other herbivores (foregut fermenters such as kangaroos and small hindgut fermenters such as rabbits , voles and possums) have digestive systems that sacrifice maximal fibre digestibility for a capacity to process large amounts of forage , even when forage fibre content becomes very high. These different digestive strategies result in the wide range of nutritional niches found among mammals.