Mark Salerno, age 10, of Utica, New York, for his question:

Why does a hippo spend so much time in the water?

The big bulky hippo may weigh four tons but his legs are quite stumpy. Though he can walk and even trot on land, he is rather clumsy. Actually, his great big body is much more comfortable in the water. Under his skin he has layers of lightweight fat and this makes his body buoyant and floatable. In the water, he moves gracefully with the greatest of ease.

Since he lives in tropical lands, you would expect the hippo's skin to be able to withstand the hot drying sunshine. But this is not so. He has a very sensitive skin that needs to be kept moist. This is one reason why he spends the day dunking and comes on land after dark. His skin has pores that give off a pink oily liquid. He seems to be sweating blood. But actually this pinkish oil helps to keep his sensitive skin moist.