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.
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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.
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