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Ocean Watch

I was recently invited to give a marine animal slide show to the second-graders of Hokulani Elementary School in Manoa. Soon after arriving, I learned that the class's terrific teacher, Anne Harrison, encourages her students to ask questions and also guides them in logical thinking.

And it shows. If there are any 7-year-olds more knowledgeable about ocean animals, I'd like to know who they are. The entire room, it seemed, was full of budding marine biologists.

A week after my talk, I received a packet of letters and drawings from these young nature lovers. Each child thanked me for coming and then asked questions. Hard questions.

Do whales have bristles? Tiara Iokepa wanted to know.

I don't know where this question came from, but it's one that occurred to me only after taking a course in evolutionary biology. In it I learned that the definition of a mammal is an animal with mammary glands and hair.

Now, most everyone knows that whales have mammary glands and nurse their young. But hair? Where's the hair on a whale?

It's there. You just have to know where to look.

Marine mammals, including seals, manatees, otters and whales, evolved from five or six groups of land mammals, such as pigs, horses, bears and elephants. The creatures that became whales and dolphins gradually lost their hair, reducing the drag on their bodies as they swam.

But traces of their furry ancestry remain on the snouts of young whales and the heads of some adults. Hawaii's humpbacks are a good example.

Humpback whale hair is easy to locate because it sprouts from golf ball-size bumps on the whales' heads. These knobs, which whalers once called stove bolts, are visible both in photos and in real life.

Today, researchers call humpback whales' head bumps sensory nodules or tubercles. Each has a follicle in it sprouting a single gray hair, ranging in length from one-half to 1 1/2 inches.

A humpback's tubercles are located on both upper and lower jaws and around the lips, much like facial hair on humans. Also like humans, each whale has a unique number and pattern of hair follicles on its face.

Humpback whale hairs contain nerves and blood, suggesting that these are sense organs. Whale hair might be part of courtship, an aid to navigation or a method of finding food.

In Hawaii, researchers have noticed that the tubercles of some aggressive male humpbacks are raw and bleeding. No one knows how this happens, but it's an important identification tool. Injured tubercles heal white, accenting their location on the whale's head. Since tubercles are spaced differently on each whale, this helps in recognizing individuals from photographs.

Humpback whales have other bristly stuff, called baleen, inside their mouths. Baleen is similar in composition to our fingernails and is rooted in the roof of the whale's mouth.

The outer sides of baleen sheets are smooth, but inside, they're frayed. These bristles of baleen intertwine to form a sieve that lets water out but keeps shrimp, fish or other prey in.

So, yes, Tiara. Whales do have bristles.

I enjoyed my visit to this remarkable class and am still amazed at some of the challenging questions these kids came up with. Before I go back there, I'm going to study.