The Koala has a greatly expanded caecum and colon where some fermentation appears to take place and where selective retention of fine particles and solutes takes place. Nutrient availability in the small intestine and rate of fermentation is affected by particle size, which in turn is dependent on mastication. The efficiency of mastication over the life of the animal is affected by tooth wear. When expressed as a function of a composite tooth wear class of a tooth row, the length of the occluding enamel edges increases to a peak then declines with extreme wear. The morphology of the teeth and the pattern of dentine exposure are important factors in the maintenance of effective occlusal morphology. Animals with very worn teeth have much larger particles and a greater proportion of these present in the stomach than animals with unworn teeth. However, the increased proportion of large particles in the stomach of older animals is accompanied by only a slight increase in the percentage of the largest size class within the caecum. Thus old animals still maintain some selective retention of fine particles as distinct from large particles in the hind gut, even though the dentition produces a lower proportion of these. This is probably achieved by an increased intake and gut passage rate.

Diet selection by immature green turtles ( Chelonia mydas ) in Flathead Gutter, Moreton Bay, was determined by examining food ingested in relation to food availability (measured as vegetation composition and abundance within the feeding site). Food composition was sampled by oesophageal lavage. Turtles were repeatedly located over a 10-week period by means of sonic telemetry and visual identification. The number of resightings indicated that these turtles remained within their feeding grounds for at least short periods of time. Immature green turtles fed on both seagrass and algal species. However, most fed selectively on algae, primarily Gracilaria sp. Food items consumed frequently by these turtles were analysed for total nitrogen, gross energy and neutral detergent fibre levels. There was a negative correlation between fibre level and the preferred food species, where the more frequently selected species had lower levels of fibre. The preferred species also had higher nitrogen levels