Facts About Whales: Their Songs and Kin

* Whales can grow to be so big because they live in water and so are almost weightless.

* Whales never sleep.

* They are "voluntary breathers," which means they consciously decide when to breathe. That way they never inhale a blowhole full of seawater.

* Male humpback whales are famous for their singing. All the whales sing the same song, which can go on for 1/2-hour and be repeated for several hours. Every year they drop some parts and add new ones. No one is sure why they sing, but scientists think it has something to do with courtship.

* Humpback whales grow to be more than 50 feet long.

* Each humpback whale has unique markings on its flukes that make it easy for scientists to tell them apart - sort of like a human's fingerprints. A humpback's flukes can be 15 to 18 feet across.

* The longest recorded dive for a humpback whale is 42 minutes, but sperm whales and bottlenose whales can hold their breath for 1-1/2 hours.

* Scientists think that whales are more closely related to cows, camels, and elephants than to any other creature.

* Whales are mammals, which means they have live births and nurse their young. A baby whale drinks about 40 gallons of milk per day, milk that has 10 times more fat than cow's milk. They stick pretty close to mom, rarely traveling even 400 yards away.

* Scientists have found fossils of a six-foot-long, hooved land animal that they believe is the ancestor of modern whales.