Digestive strategies in ruminants and nonruminants

Of the 176 species of ungulates in the world the great majority (146 species) are ruminants. The more recent ruminants probably have displaced the older nonruminants because of their superior digestive system in combination with the ruminantion mechanism leading to significant advantageous differences in important life history traits. Nonruminants like hippos, equids, elephants and tapirs reach sexual maturity at a later age and produce fewer young per year than ruminants, relative to body size.

Within the ruminants three different adaptive syndromes in feeding style are distinguished and expected differences in digestive physiology between members of the various feeding styles were tested. Nonruminants are poorer fibre digesters than ruminants while the large bovid 'grass and roughage feeders' have superior capacity for digesting fibre.

In some areas in the world, notably in East Africa, species-rich ungulate communities can be found. Various guilds of species occupying different habitats and feeding niches can be distinguished and the species belonging to different guilds are sufficiently dissimilar as not to compete with each other. Within guilds frequently groups of species of similar body weight and with similar ecology occur sympatrically. The apparent peaceful co-existence of these species yet has to be explained.