Quantitative Macroscopic Anatomy of the Giraffe (Giraffa camelopardalis) Digestive Tract.

Quantitative data on digestive anatomy of the world's largest ruminant, the giraffe, are scarce. Data were collected from a total of 25 wild-caught and 13 zoo-housed giraffes. Anatomical measures were quantified by dimension, area or weight and analysed by allometric regression. The majority of measures scaled positively and isometrically to body mass. Giraffes had lower tissue weight of all stomach compartments and longer large intestinal length than cattle. When compared to other ruminants, the giraffe digestive tract showed many of the convergent morphological adaptations attributed to browsing ruminants, for example lower reticular crests, thinner ruminal pillars and smaller surface area of the omasal laminae. Salivary gland weight of the giraffe, however, resembled that of grazing ruminants. This matches a previous finding of similarly small salivary glands in the other extant giraffid, the okapi (Okapia johnstoni), suggesting that not all convergent characteristics need be expressed in all species and that morphological variation between species is a combination of phylogenetic and adaptational signals.