Caribou Digestion: Ruminators Chew Their Cud Ruminate and Chew Ruminate: to a chew again what has been chewed slightly and swallowed : chew the cud. You may remember that Caribou belong to the class, Artopdactyla, described as “even-toed ruminants.” Ruminates are animals that possess complicated digestive systems. Their stomachs are divided into parts, each part taking a different role in breaking down and absorbing nutrition from the food they eat. Other animals in this class are cows, deer, horses and pigs. Four-chambered Stomach Caribou possess a special 4-chambered stomach and digestive system that allows them to thrive on rough vegetation low in nutrition but available in big quantities. Because they do not chew before swallowing, a lot of undigested food accumulates in the first stomach, called the rumen. Caribou can feed for over an hour or more to fill up their rumen. In the rumen bacteria begin breaking down the course plant material. Photo courtesy USGS Lying Down on the Job Once the caribou has eaten they find a place safe from predators to ruminate, or further process their food. Now the food is brought back up (regurgitated) in small amounts called cud. The caribou chews its cud with its back teeth (molars) until it is reduced to a pulp then it is swallowed again. This can be a long process because all the food in the rumen is processed this way. When the caribou swallows this time, the food bypasses the rumen and goes into the second and third chambers. These are called the reticulum and the ommansum. In these chambers excess water is removed from the food. The fourth chamber, called the obamassum is where nutrients are absorbed and sent into the bloodstream. This chamber is most like the human stomach. No Such thing as a Buck-toothed Caribou If you examine the jaws of a caribou skeleton you will discover that the caribou has no top incisors or front teeth. You will find bottom incisors and in the back both upper and lower grinding teeth. Open the mouth of a live caribou and you will find that the roof of its mouth has a thickened callous pad the cutting teeth or incisors of the lower jaw can press in to rip or chop off the food they find. Try This Investigate and find a diagram of a 4-chambered stomach. Draw a picture of a caribou showing a cutaway of the stomach. Diagram the drawing and label the parts. Describe how the stomach parts work. Copyright 2003-4 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form