Christy Epp, age 10, of Visalia, California, for her question:

Why does a cow have four stomachs?

The cow grabs a mouthful and swallows it whole. It goes down to the first compartment of her stomach and soon she has swallowed a whole meal. However, that tough grassy food must be properly chewed before the other compartments of her stomach can digest it. So it's time for the cow to chew her cud. With a little cough, she brings up a wad of food, chews it thoroughly and swallows it again. This time it goes down to other compartments where it is digested.

Actually a dairy cow does not need a stomach with several compartments, but her ancestors did. They lived in the wild, where hungry enemies waited to pounce on them. Grazing out in the open was not very safe and chewing takes a long time. So they swallowed a quick meal and went off to chew the cud in a safe shady wood. Our dairy cow is not likely to be attacked by large wild animals. But she inherited her fancy stomach from her ancestors.