The digestive tract and life history of small mammals
The type of food, differentiation of the large intestine and stomach, and methane production, as well as life history data, are considered in Insectivora, Rodentia and Lagomorpha.
When food containing plant cell wall material is eaten, there is either a differentiation of the stomach or the large intestine. In animals with low body mass and little differentiation of the gastrointestinal tract, methane production is low, but structures essential for microbial digestion of plant cell wall material, such as haustration of the colon or formation of a caecum, can be found in many methane-producers. Animals with a body mass < 500 g and a weaning time < 20 days are non-producers of methane. Establishment of a balanced microbial population in the gastrointestinal tract requires some time. Many non-producers of methane wean their young in < 10 days, but many producers need > 50 days for the weaning process. Caviomorpha, Thryonomyidae and Hystricidae seem to have 'opened the door' to the use of low quality food by microbial fermentation, but some of them have to 'pay' for this extension of the food range by an extended weaning period, which also means an extended dependency on the mother.
Mammal Review. Vol. 32, no. 2, pp. 107-131. Jun 2002.