1. Squirrels belong to the order Rodentia. There are 365 species.

2. They mate twice a year.

3. Their nests are called dreys.

4. Their sweat glands are on their feet.

5. They can run 20 miles an hour.

6. Their teeth never stop growing. Gnawing keeps squirrels' teeth from growing into their necks.

7. When frightened, they dart back and forth to confuse predators. This doesn't work with cars, however, so most city squirrels don't live longer than a year.

8. Although considered granivores (animals that eat grains and nuts), they will eat almost anything.

9. Gray squirrels bury their acorns all over the place ("scatter hoarding"), then forget where. Forgotten acorns become trees. This forgetfulness is the main way oak and other hardwood forests grow and spread, scientists say.

10. Gray squirrels are called "living fossils" because they haven't changed much in 37 million years.