Ocean
Watch
Monday, December 15, 1997
It’s unlikely shark killed
whale at North Shore
Last week, a 20-foot-long juvenile sperm whale washed
up dead at a beach park on the North Shore.
Biologists said they didn't know the cause of death,
but that didn't stop people from speculating. One observer said, "I
think a shark did it, because you have plenty of sharks out there."
Good guess but probably wrong. Sharks aren't that
stupid. Because to mess with a healthy sperm whale, even a young one, is
asking for big trouble.
Sperm whales are the largest of all toothed whales.
Males grow up to 60 feet long and weigh up to 58 tons. Female sperm whales
are smaller, growing to "only" 37 feet long.
Although they are big and have a mouth full of enormous
teeth, sperm whales also find safety in numbers. These are sociable
animals, usually traveling in groups of up to 50. During peak breeding
season, from late winter to late summer, sperm whales can gather in groups
of up to 150 whales.
Such groups consist either of bachelor bulls, or of
females and their young accompanied by one or more large males. When not
traveling with their harems, these large males roam the world's oceans
alone.
And roam they do. Sperm whales cover a tremendous area,
traveling from the tropics all the way to the ice packs of both Northern
and Southern hemispheres.
They can also be found at a wide range of depths, from
the surface, where the spray from their blow hole is distinctively angled,
to 10,000 feet down.
What are sperm whales doing at those cold, dark depths?
Eating giant squid and octopuses. These whales sometimes bear round sucker
marks on their skin from their battles with the big cephalopods. A 36-foot
long squid was once found in a sperm whale's stomach.
Although squid and octopuses are sperm whales' main
food, an amazing variety of other things have been found in their
stomachs: seals, lobsters, sponges, crabs, jellyfish, rocks, sand, glass
fishing floats, coconuts, wood, apples, fishing line, shoes, and of
course, the ubiquitous scourge of the ocean, plastic bags.
Researchers also recovered a 10-foot blue shark from
the stomach of a large male.
And that's why it isn't likely sharks caused the death
of the young Oahu sperm whale. Any whale that can swallow a 36-foot giant
squid or a 10-foot shark isn't likely to fall prey, or let its offspring
fall prey, to a shark, even a big one.
Sure, the carcass of this 20-foot-long whale had
several shark bites on it, and sharks were spotted in the vicinity. But
that's normal for any carcass drifting in the ocean. Sharks are part of
nature's recycling system.
Even though sharks may not be much of a threat to sperm
whales, the whales do have two formidable enemies: killer whales and
people.
Since killer whales can eat just about anything they
come across, they occasionally attack and kill a sperm whale.
People once attacked and killed sperm whales
relentlessly, but sperm whales didn't usually go down without a fight.
This is, after all, the legendary species that sent sailors flying through
the air, smashed their whaleboats and killed Captain Ahab.
Commercial hunting of sperm whales began in 1712 when
people discovered that the material in the whales' heads made good lamp
oil. The most intense hunting came during the Yankee whaling era of the
1800s and the factory ship whaling of this century.
The good news is that although certain populations have
been depleted, the sperm whale today is the most abundant of all the great
whales.
Sperm whales are spotted occasionally around the main
islands but are more common in the waters of Hawaii's northwest chain.
Ancient Hawaiians carved pendants from the teeth of
whales that washed ashore but did not hunt sperm whales.
