Charles Swisher, aged 10, of Penna., for his question:

How big is a hippopotamuses tooth?

Mr. Hippo has the largest mouth of any land animal. And he loves to open it wide and show off his huge teeth. These teeth are big and strong enough to snap a crocodile in two. They keep him safe when the crocodiles invade his river.

His teeth are also well suited to ripping up water plants. The two lower tusks are the biggest. They are shaped like sickles. His huge, chomping teeth in the back of his mouth are kept sharp by grinding upon each other. Mr. Hippo can tear up and chew the toughest plants with those teeth.

The big lower tusk teeth may grow to be two feet long. But half of them are hidden in his gums. So when he opens his mouth you only see about one foot of tusk ‑ which 1s enough:

The hippo’s tusks may weigh seven pounds apiece. They are sometimes sold as ivory. But they are more brittle than the ivory of the elephant's tusk.