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At 45 feet and just as many tons, the Humpback
Whales of the northwest Pacific congregate each summer to feed in
the waters of southeast Alaska and journey each winter to the tropical
breeding grounds of Hawaii.
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The fifth largest of the great whales, Humpback calves are born weighing
an average of 1.5 tons and live to over 40 years of age.
Hunted in the early part of this century, the Humpback population was
reduced from 15,000 whales to less than 1,000 by 1966. By 1993 their numbers
were thought to have increased to approx. 3,000 and today seem to be holding
steady.
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Humpbacks
are named for the distinctive arch thier backs make when diving.
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Other identifying
features include the small dorsal notch on the back, elegant flukes and
extraordinarily long pectoral fins - which gives rise to their scientific
name: megaptera noveangiliae (translation: Big Wings of New England).
Classified as a Cetacean -
or marine mammal - Humpbacks are warm-blooded, give birth to live young,
use lungs to breath and retain similar sensory organs to ours - eyes,
ears, nose (blowhole) and are thought to be descendants of land mammals
similar to present day cows.
Humpback flukes are used to propel the animal through the water at speeds
between 1.3 to 5 knots per hour. The flukes are also used in a behavior
known as tail lobbing whereby the body of the whale is under water and
the tail is held up high and then brought down with considerable force
on the water. The resulting slap! travels for miles both above and below
the surface and may be used to communicate with whales at quite a distance.
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Most often, the underside of the fluke has
a unique black and white pigmentation pattern that allows for easy
identification of the individual.
Some flukes are entirely black, in which case the shape of the fluke
becomes its identifying character. Other times, a notch or tear
in the fluke provides the necessary information.
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Whales are generally categorized into two groups: toothed whales (odontoceti),
such as the Orca or Beluga, and baleen whales, such as the Humpback and
Grey whale, whose mouths are lined with fingernail-like baleen fringes
which act as a filter to release water from the mouth while keeping prey
inside. These whales are referred to as Mysticete whales or "mustached"
whales.
In summer, Humpbacks feed on two types of food - Krill (tiny shrimp-like
creatures) and Herring. When the catch is Krill the Humpbacks dine alone
or in pairs - diving and surfacing through dense patches of feed for hours
at a time.
When Herring is on the menu, it seems more efficient to coordinate efforts
with other whales in a behavior known as lunge or group feeding. Lunge
feeding begins with a staggered dive of whales which encircle a group
of Herring in an underwater trap known as a bubblenet. As the bubbles
rise, a whale trumpets a feeding call for to a minute or two before sweeping
the frequency upwards to cue a synchronous surface lunge. A hydrophone
isn't needed to hear these sounds. They travel up through the hull and
into your ears. 160 decibels of Miles Davis meets the long-lost Indian
guru. Riffs, blasts, swoops and screams. A trumpet section out on the
loose.
 Between mid
October and November the feeding stops in Alaska and the whales swim to
the warm protected waters of Hawaii for the breeding and birthing season
- a 2,818 mile (4535 km) journey that has been documented as taking as
little as three weeks.
In Hawaii, the Humpbacks display another quality of vocalizations - the
Humpback's famous mating song. Floating upside-down, the Winter Song comprises
a wide-sweeping range of low grunts to high whistles and is sung exclusively
by the males.
The song lasts between 20 - 35 minutes with each whale singing the
same arrangement of verse, chorus, verse - though not in unison. Whereas
in Alaska the Humpbacks maybe vocalize once every twenty minutes, the
Winter Song is a continual presence in the waters of Hawaii.
An interesting feature of the song is that it begins each season where
it left of previously and incorporates new refrains as the season progresses.
These iterations could perhaps be compared to sonic tree rings marking
the passage of time or to a type of oral history which expands to contain
current events.
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(click
to hear Winter Song)
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The
Winter Song is thought by some researchers to act as sonic antlers
- either to attract females to the singer by the qualities of his
call, or to repel competing males by a show of sonic strength.
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Other researchers have noted that the intricate cycle of phrases and
themes seemed to resemble each other in a type of sonic poetry. To delve
more in depth into the possible functions of these sounds, please visit
the Listening Underwater section.
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