Marilyn McMahon, age 10, of Peterboro, Ontario, Canada, for her question:

Why do frogs croak?

Nature's animals sound off with a zillion different voices. But one of the first of them to have any voice at all was the frog. This was many millions of years ago, when the amphibian ancestors of the toads and frogs were the most important animals on earth. The frogs of those ancient days took in gobs of air and let it out to sound off, just as they do to this day. But there was nobody around to translate what they had to say. And after all this time, we still are unable to translate the croaks of our frogs or the various notes and chirps of the frog and toad glee club.

Modern experts tell us that the    croaks of a frog can be understood by other frogs. They suspect that bull frogs croak serenades to impress lady frogs. Andy suspects that they also croak just for the fun of hearing their own voices. And if you have a tame or half tame frog in your garden, he may do what Andy's pet frog does, croak a husky "Hello" when you go near him.