Squirrels don't always get that much appreciation from humans, but they have a long history of living in our midst. There are more than 200 squirrel species worldwide and they're native in every continent except for Australia and Antarctica. They range in size from the five-inch African pygmy squirrel to China's flying squirrel which can grow up to 3 feet long. All squirrels have four front teeth that are constantly growing to help them endure their constant gnawing.