"I'm delighted by the shape she's in," said Corrine Davis, a pathologist
with the University of California at Davis. "Her tissues are in far better
condition than I expected."
And a lot of tissue it was: about 1,700 pounds worth. That's not
particularly big for a great white shark, but then, Pangea was a mere
adolescent. At 10 to 12 years of age, she was not even sexually mature.
Still, she had what it took to be a fearsome ocean predator: a 14-foot
length, jaws that could extend to a 24-inch diameter, and a maw bris with teeth close to 2 inches long.
When alive, she no doubt sheared the head off many a harbor seal -- a
favorite killing technique of great whites. Had she chosen, she could have
done the same to a surfer.
But now she was only so much sashimi, the victim of a commercial
fisherman's gill net near Morro Bay. Being apex predators, great white sharks
are quite rare. Still, they occasionally entangle and suffocate in nets set
for halibut.
Biologists consider such incidents great opportunities. Despite all the
hoopla, relatively little is known about great whites, and it is difficult to
obtain specimens for dissection.
"We first heard about Pangea when we found out she was being offered for
sale on EBay," said Sean van Sommeran, executive director of the Pelagic Shark
Research Foundation, a Santa Cruz group devoted to the conservation of Pacific
fisheries. "Most of the time you don't even hear about these nettings. The
fish are chopped up and sold surreptitiously. The meat, fins and jaws all
bring a lot of money."
Bids for Pangea -- named by researchers after an ancient continent that
once dominated Earth -- reached $4,200, but Van Sommeran said he was able to
obtain the critter for $700 after negotiating with the fisherman who captured
her.
So biologists from state agencies, the University of California and
environmental groups gathered at California Department of Fish and Game
laboratory to see what could be learned from Pangea by dismantling her.
Great whites are protected under state law, Van Sommeran observed, but the
regulations are vague about what can be done with fish caught while legally
fishing for other species.
Gill nets aside, researchers said they hoped to learn a lot about great
whites through Pangea.
"Among other things, we're going to take vertebral and DNA samples from her
to compare them with samples from great whites taken in other places, such as
Australia and South Africa," said Dave Ebert, a shark researcher who led the
dissection.
Great whites are distributed worldwide, observed Ebert, but it is not yet
clear if there are significant genetic differences between the populations:
whether there are distinct subspecies and races, in other words.
"My sense is there isn't," said Ebert, "but that's why we're doing the
research."
The dissection tools used on Pangea weren't particularly delicate. Butcher
knives were the favored device, and pruning shears and meat saws also were
available.
Every inch of Pangea was meticulously measured, and samples were taken of
her tissues to test for environmental contaminants.
Researchers weighed her gigantic liver, which constituted almost a fifth of
her weight.
"Great whites store lipids (fat) in their livers, which serve them both as
a buoyancy device and a source of energy," explained Van Sommeran. "They can
go a long time without eating because of the reserves in their livers."
But that doesn't mean great whites like to fast. Quite the contrary. With a
few related species such as porbeagles, salmon sharks and makos, great whites
are unique among sharks: They are essentially endothermic, or warm-blooded.
"They can maintain body temperatures 18 degrees above water temperature,"
said Scot Anderson, an independent shark researcher who has worked for the
Point Reyes Bird Observatory and the Gulf of the Farallones National Marine
Sanctuary.
Maintaining such internal temperatures keeps muscles warm, allowing great
whites to move rapidly and decisively while hunting, Anderson observes. But
temperature regulation is also expensive in terms of energy expenditure --
which is why great whites love to eat seals.
"Seals are really fat," said Anderson. "They're just like big sticks of
butter, loaded with energy. When great whites sense seals, they get really
turned on. With fish, they may eat them, may not, but they always go for the
seals."
Great white sharks find seals by smell, homing in on urine and feces trails
through the water.
"They have very large olfactory bulbs (in their skulls), so we know that
odor plays a major role in finding prey," said Davis, "and they also use other
senses."
Sight, for one. Great whites see well. But they also use little bumps on
their snouts called ampullae of Lorenzini.
"They determine water pressure, temperature and electrical impulses from
the ampullae," Davis said.
There were other things on Pangea's head: scars, lots of them, including
two fresh rakings that matched the typical tooth patterns of a sea otter.
"Great whites eat marine mammals, and marine mammals have teeth and claws
and fight back," Van Sommeran said.
Pangea disappointed the researchers in one regard: Her stomach was empty.
No elephant seal teeth, sea otter bone fragments or corroded Rolexes.
Great whites are handsome animals in the water, graceful and subtly colored
in gray and white; Pangea, in the end, was reduced to a pile of fish fillets,
though ones carved with science in mind, not the seafood counter.
Still, the researchers didn't lose sight of the fact that they were dealing
with an animal that remained compelling even in death.
Davis rubbed her finger along Pangea's skin, noting the sandpaper texture.
"The skin is composed of denticles, which are actually tiny teeth," she
observed, "I mean, literally teeth. They're essentially identical to the teeth
in her mouth, though smaller. Actually, you can say her teeth are modified
scales."
Brandy Faulkner, director of molecular biology for the Pelagic Shark
Research Foundation, said she hopes more people become educated about the true
nature of great whites.
"Of course they're a top predator, but what isn't recognized is how
intelligent and well-behaved they are," she said. "They never rush the bait
bag or the boat when we're tagging them. They're incredibly wary. They spy hop:
stick their head out of the water and look around, like whales. They're not
dumb fish."
