A really big family - sperm whales; includes related article on tracking the whales

Ranger Rick, Jan, 1997 by Deborah Churchman

If you were a sperm whale, every member of your family would be big. We're talking humongous here. Adult sperm whales may be bigger than a school bus. In fact, a male may grow almost as long as two school buses end to end. And he may weigh as much as 60 tons (54 t).

A sperm whale heart alone weighs 400 pounds (180 kg). And a sperm whale's brain is bigger than the brain of any creature that's ever lived!

BIG BABIES, CLOSE FAMILIES

Here's how these families work: Sperm whales travel around in groups called pods. Each pod is made up of a dozen or so female adults from the same family and their young.

Females give birth to enormous babies. If you were a sperm whale baby, you might be 12 feet (3.6 m) long--and weigh a ton (900 kg)!

And you would be a really big eater. Baby whales need lots of food to grow larger. Because they're mammals, the babies drink milk from their mothers--more than 40 pounds (18 kg) each day. And is it ever buttery! A sperm whale's milk is 24% fat. (Cow's milk is only 3.5%.)

To feed herself and her baby, a mom needs to eat hundreds of pounds of food each day. Other members of the pod help take care of her baby while the mom is busy. Sometimes the other whale moms will even feed their own milk to the baby. And they'll take turns staying close to protect the baby from attacks by sharks or killer whales.

WHAT'S FOR LUNCH?

During the day, pod members must spread out and dive for prey. It takes a lot of fish and squid to feed a whole pod!

The whales dive down deep to get their food. No one knows for sure, but sperm whales may dive deeper than any other air-breathing animals on Earth. (One reason is that they can go for a l-o-n-g time without breathing--more than an hour!) Sperm whales may be able to dive down more than a mile (1.6 km) deep.

It's very dark in the deep ocean. So how do sperm whales find their prey? Some kinds of prey, such as squid, are luminescent (loom-in-ES-sent). That means they glow in the dark.

But whales have a way to find prey they can't see--they use clicking noises. The noises bounce off anything that's in front of the whales. When the noises echo back, they show the whales where to locate the prey. Finding prey this way is called echolocation.

Sperm whales eat mostly small squid, which are easy to catch but not much of a meal. The whales also eat sharks and other fish. But a really good meal for a sperm whale is a 400-pound (180-kg) giant squid.

Giant squid are NOT easy to catch--they put up quite a fight. How do we know? From the scars often found on an adult sperm whale's head. The scars are made mostly by the sharp beaks and suckers of giant squid.

Sperm whales can eat many different foods. So if one kind of food gets scarce, they can eat something else. And if food gets really scarce in one part of the ocean, older whales can remember where else they can go to find the right prey. (Whales can live for up to 70 years.) Younger pod members just follow the older leaders.

CLICK COMMUNICATION

Sperm whales also use their clicking sounds to "talk" to each other. In the afternoon, pod members get together and start clicking in patterns. Scientists call these patterns "codas." They think different codas may mean different things to the whales, such as "Hello" or "Go away!"

During this social time, pod members swim together close to the surface, clicking these codas and touching each other. That may help the group feel close and friendly--like when you share time with your family.

WHERE ARE THE MALES?

When males are about six years old, they separate from their families. They swim from their warm-water home to cooler waters to look for food. The oldest males wind up in the icy waters of the Arctic or Antarctic.

And that's a good thing. Males grow to be as much as three times heavier than female sperm whales. If they stayed where the females and young were feeding, the males wouldn't be able to find enough food for themselves.

TIME TO MATE

After young males leave home, they spend almost 20 more years just eating and growing. But starting sometime in their mid-20s, male sperm whales roam back to where the females live. Why? To mate.

When a male swims near a pod, he makes a click so loud it sounds more like a clang. He's letting other males know that he is nearby. Smaller males stay out of the way when a bigger male starts clanging.

Scientists used to think that each adult male found just one group of females to hang out with. Now they've learned that a male roams from pod to pod, look- ing for females that are ready to mate. Then, after mating, he leaves.

After 15 months, a female gives birth to her one-ton baby. She rolls onto her side to give birth. That way the baby is born near the surface, where it can take its first breath. Then the mother and the other females in her group help the baby grow up--in a BIG family.

Cruising with the Clickers

How do you follow animals that live where you can't easily see them, that dive thousands of feet deep, that swim thousands of miles each year, and that, at first glance, all look pretty much alike?