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| "Wmmff! Smell that fresh air!" That thought might be in the mind of this humpback whale as it breaches the waters of the Arabian Sea. Whales have been known to breach continuously for 90 minutes, making as many as 100 leaps in a row. |
Activities
As we
cling to the sides of our small rubber boat bouncing around on a sea of foam,
we finally find what we’ve been seeking. No, we aren’t shipwrecked sailors searching
for land. We are marine biologists on the lookout for whales in the Arabian
Sea, off the coast of Oman. Suddenly, a leviathan heaves itself out of the
water and crashes back down again, creating a wave that threatens to sink our
boat. Then it slaps its tail and long fins on the water’s surface and sends up
sheets of fishy spray—forcing us to shield our cameras. Finally, exhausted by
its efforts, the creature lifts its tail and slides noiselessly back into the
deep.
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| "What kind of whale is that?" wonders a member of the Oman Whale and Dolphin Research Group. Founded by Omani and international volunteers in 2000, the group tracks marine mammals through the waters off the southern Arabian Peninsula. |
We excitedly compare
notes, trying to estimate the whale’s vital statistics. Such aerobics would be
impressive if executed by a half-ton trained sea lion, but this is a humpbacked
whale, some 12 meters (39') long and with a likely weight of around 35 tons.
We’re about to restart our engines when an unearthly noise shakes our boat. It
sounds like a deep chainsaw, then sweeps up to a shrill chimpanzee whoop. We
drop our underwater microphone over the side and record the sound. Our whale is
singing, a noise created by forcing air through massive air cavities in its
head. Only male humpbacks sing, and they do it only during the breeding season.
We’re not sure whether this is to discourage rivals or to attract a mate—perhaps
it’s both. To us, it doesn’t sound like much of a love song, but it could help
us understand how this whale is related to other whales that inhabit waters
farther south.
You may not think that
the Arabian Sea is home to an abundance of marine life, but our team from the
Oman Whale and Dolphin Research Group has been very busy indeed. We’re spending
a month on an annual field trip to the remote Hallaniyat Islands, 100
kilometers (62 miles) off Oman’s southern province of Dhofar. We hope the trip
will help us understand more about the mammals living in these waters. It’s
slow and painstaking work, and we’re using every research method at our
disposal, including recording whale songs and taking DNA samples. Our transport
is a 28-meter (93') oceangoing sailing dhow. Her slow speed is ideal for our
purposes, and she comes equipped with a small inflatable boat that enables us
to get close to any action, provided, that is, we can find some animals to
study.
Sometimes it is difficult
to find the whales! They’re big, but the ocean is a whole lot bigger. We search
in areas where we know they might feed. That’s why we chose this particular location.
Beneath us are underwater cliffs where the seabed plunges from a few hundred
meters’ depth to more than a thousand (3250'). These are prime hunting grounds
for squid and a good place to find sperm whales—the squid’s most fearsome
predators.
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| The flukes of a blue whale stand out in sharp contrast to the distant mountains of Oman, just before it slips into the depths. |
Soon our efforts are more
successful than we could have hoped. In front of our boat we see a group of 50
sperm whales. These giants of the deep may look gentle but they are the world’s
largest predators. They are capable of diving to depths of 2000 meters (6500'),
where they stun squid with sonic clicks created in their enormous blunt heads.
Now they are floating on top of the water, enjoying the bright sun, and taking
turns sending up spouts of water. Then, one by one, each lifts its tail for
another dive.
We record our encounters on sighting sheets, and
the stack of them attached to my clipboard offers proof of our action-packed
week: 3000 long-beaked common dolphins; smaller groups of Rissos dolphins; a
secretive beaked whale, glimpsed so briefly that the exact species can’t be
confirmed; four rare blue whales, each the length of two London buses,
frolicking just offshore; and finally, three lone humpbacks. The humpbacks lure us
in with their siren songs and allow us close enough to get a shot at them with
our crossbow and biopsy dart. It’s a tricky operation, but worth the effort: The
dart’s hollow tip collects genetic material invaluable to our work here.
We are happy to know that
marine life in the Arabian Sea is flourishing, but we are also a little
puzzled. These tropical waters are crystal clear and show no sign of the green
algae generally needed to support a mass of marine life. So, where is the food
coming from? The answer lies thousands of kilometers to the east.
During the summer months, temperatures in Oman’s capital, Muscat,
climb to a sweltering 50 degrees Celsius (122° F). But farther south, the
climate is very different. From the spring equinox through summer, warming air
over southern Asia creates a powerful weather system known as the southwest
monsoon. Rain-filled mists transform the dusty landscape into a lush garden,
while winds whip the sea into a frenzy of foam.
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| Whales aren't the only mammals that live and breed in the Arabian Sea. Here, a common dolphin calf leaps alongside an adult. |
During the monsoon, known
locally as the khareef (“the time of ample rain”), fishermen pull
their boats high up the beach and tend to their nets. While these storms
prevent them from putting out to sea, they are vital to the following year’s
catch. “The strong winds stir cold, nutrient-rich water up from the deep. It
kick-starts the entire food chain,” says Fergus Kennedy, a marine biologist
working with our team.
Humpback and blue whales
are baleen whales. This means that, despite their huge size, they feed
exclusively on small fish and crustaceans. They filter these creatures from the
seawater using comb-like rows of springy, bristle-edged plates in their mouths
called baleen, or whalebone. Scientists used to think these whales migrated
twice a year to find the vast quantities of food they need to sustain
themselves. That is, they left the warm winter breeding grounds of the tropics
to converge on summer feeding grounds at the North and South poles. By all rights,
then, we should only expect to see whales here in the winter months—yet, we
were seeing them year-round. Why weren’t these whales migrating?
“Oman is in the northern
hemisphere, and you’d therefore expect Oman humpbacks to spend the northern
hemisphere’s summer in the Arctic,” explains Gianna Minton, another team member.
“However, one look at a world map shows the difficulties involved in that sea
trip.” The route to the Arctic from the Arabian Sea is entirely barred by the
African and Asian land masses. However, the route to the other pole—the
Antarctic—is clear. Could the whales be making the longer round-trip to feed there
instead?
Given that whaling killed
so many of these enormous creatures in past decades, it is ironic that much of
our knowledge of these animals comes from data recorded by those involved in
the whaling industry. The catch data published by countries that often hunted
whales in the Arabian Sea, such as the former Soviet Union, provided the key to
unlocking what has been called the “Arabian enigma.” Minton explains that
around half the female humpbacks caught by the Soviets were pregnant, and that
“the state of development of the calves suggested that the humpbacks were
breeding here between January and May. It’s what we’d expect from a
northern-hemisphere population, but it meant that they couldn’t be traveling to
the Antarctic to feed. By the time they’d finished calving, it would be the
southern-hemisphere winter.”
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| Whale DNA can provide such basic information as gender. It can also help explain the relationship between populations of whales. In this photo, a researcher prepares to gather genetic material with a crossbow and a hollow-tipped biopsy dart. |
Adding the Soviet data to
our evidence of year-round sightings seemed to suggest only one conclusion: The
whales were relying on the monsoons to “kick-start” the food chain and provide
them with the nourishment needed to sustain them here for 12 months of the
year. They weren’t migrating at all!
The results from our other
research methods, including DNA analysis, point to the same conclusion.
Humpback whales within any given geographic area tend to sing the same song,
and this can vary greatly from one population to another. The songs of Oman
humpbacks, however, have little in common with nearby populations off the east
coast of Africa. This fact strongly suggests that the two populations have not come
into contact with each other.
While the whales may stay
in the waters off Dhofar year-round, we cannot. The winds are beginning to pick
up, signaling the start of the khareef.
We pack up our equipment and prepare to return to Muscat. We’d like to stay
longer, but we know that the gales that evict us from the sea will sustain
these leviathans until we return again.
Notes:
Leviathan is a term used
to describe a monstrous sea creature.
Biopsy darts are designed
to collect a tissue sample from an animal when you have to do it from a
distance.
An enigma is a puzzling
or unexplainable situation.
click here to view the original article
| Anna
McKibbin is a writer and photographer focusing on natural history and
the environment. She is a trustee of the Indian Ocean Research and Conservation
Association, a non-profit committed to the conservation of natural resources.
She can be reached at [email protected]. |
STANDARDS
This lesson correlates to the following national standards for world history and language arts, established by MCREL at http://www.mcrel.org/:
