Factors affecting the volume and macrostructure of gastrointestinal compartments in the tammar wallaby (Macropus eugenii Desmarest)

We explored the factors that govern the length, wet tissue weight and wet d igesta content of the gut components of 100 tammar wallabies (Macropus euge nii Desmarest) shot on the same night, by multivariate (discriminant) analy sis and by allometric analyses based on simple linear regression, and on re duced major axis regression. The slope coefficient of the regression descri bing variation of whole gut content with body weight was not significantly different from isometry. Similarly, stomach length, content and tissue weig ht scaled isometrically with body weight, as did small intestine tissue wei ght and content and colon content. Colon tissue weight scaled allometricall y with body weight. Length of caecum scaled to body weight was similar to t hat of browsing species, shorter than that of gazing species and varied wit h body size like that of larger species. Length of small intestine scaled t o body weight was shorter, and length of colon longer, than that of similar -sized grazing species. There was a sexual dimorphism in gut morphology, fe males having a relatively greater amount of tissue in the stomach and colon , and a relatively longer caecum and colon. There was a reciprocal variatio n in the weight of digesta in stomach and hindgut, suggesting that hindgut content was evacuated as feeding proceeded. It appears that the hindgut may contribute to overall digestive strategy under conditions when reduction i n feeding rate brings about a relative emtpying of the stomach.