Allan Carlow, age 11, of Indian River, Ontario, Canada, for his question:

Are crocodiles and alligators the same?

These two look alikes are cousins, rather than brothers. But we don't have to risk giving them physical examinations to tell which is the crocodile and which is the alligator. We can distinguish them by their facial features, especially their facial expressions. The crocodile's long snout is narrow and rather pointed. The alligator's long snout is wider with a more rounded tip. The crocodile always wears a wicked grin; the alligator never smiles.

The different facial expressions arise from a similar dental problem. Both have some extra long teeth in the lower jaw and if this problem were not solved, neither could close his big mouth. The alligator has pits in his upper jaw. When he shuts his mouth, his long lowers tuck into these matching pockets    and out of sight. The crocodile has matching grooves on the outside of his upper jaw. When he shuts his mouth, his long lowers slide up into these shallow slots. However, they protrude somewhat and push up his top lip. This gives him that unmistakable crocodile grin.