Francis Ogrino, age 10, of Cleveland, Ohio, for his question:

How long does the slider turtle live?

The slider is our favorite pet turtle. He began life, of course, as an egg. Chances are he hatched with maybe ten brothers and sisters in the Mississippi Valley. Year by year, the young slider grows and adds to the size of his shell. At the age of three, he may be a flattish turtle, about three inches long. His basic color is muddy green. There are yellow streaks on his head and neck and a half circle of bright red around his head. Soon he is ready to find a mate, but his wife will be a larger turtle. As he grows older, Mr. Slider grows darker and darker.

Like most of the easygoing turtles, he has a long life span. With luck, he can expect to celebrate 40 and, perhaps, 50 birthdays. His life in the wild, however, is full of foes. Maybe five of his ten brothers and sisters will be caught and devoured by skunks or raccoons. One or two may be captured as infants and swallowed by snakes.  And hungry snakes also raid nests of turtle eggs. Other relatives will be captured by human beings. The slider has about one chance in ten of reaching old age.