About 150 different types of animals have multiple compartments in their stomachs, including cows, sheep, camels, yaks, deer and giraffes. Animals with multiple stomach compartments are known as ruminants, named after the part of the stomach called the rumen.
Ruminants may be described as having four stomachs, or as having a stomach divided into four parts, called the rumen, the reticulum, the omasum and the abomasum. This type of digestive system allows ruminants to extract additional nutrients from food through a process of regurgitating and re-chewing food. The term pseudoruminants refers to animals that have a stomach with three sections, such as the hippopotamus.