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| A magnificent visitor | | December
29, 2002. |  Year
after year, the waters that bathe the shores of the Bay of Banderas get ready
to welcome a magnificent visitor: the humpback whale.
This
cetacean that belongs to the balenopterid group makes a voyage of thousands of
miles from its feeding grounds in the Bering and Chukchi Seas to its winter refuge
along the tropical coasts of the Mexican Pacific. One of its meeting points during
the months of November to March is right in front of Puerto Vallarta, where it
goes through its courtship, mating and birthing processes. It also engenders the
admiration of tourists with demonstrations of its acrobatic abilities and spectacular
ballets. The humpback whale (Megaptera novaeangliae) has
a stocky body, measuring 10 to 15 meters in length (30-45 feet) and weighing some
30 tons. Its skin is shiny black, most often covered with encrustations on the
head and around the breathing holes. These cause much scarring, making the animal
appear whitish. The whale also has numerous ridges or wrinkles around the throat,
as well as a "hump" made of fat, visible when it breaches prior to diving. One
of the most conspicuous features of this giant of the seas is the length of its
pectoral fins that can measure as much as a third of the animal's total length
(3-4 meters or 9-12 feet). This unique feature that sets it aside from other whales,
and thus its scientific name of Megaptera, which means "great fin" or
"great arm" in Greek. Like fingerprints do for
humans, the patterns of notches and light and dark marks visible on the dorsal
fins enable observers to identify each individual. Humpback
whales live in many areas of the oceans in both hemispheres. At times, they will
go into bays and large rivers (i.e.: the St-Lawrence). There is a famous story
that tells of the entrance of a whale into Tay Bay in England. It remained there
for six weeks before it beached itself and was captured. During
the cold winter months in the northern hemisphere, they migrate to the warm tropical
waters, only to return to the polar regions in the summer. Due to the inversion
of seasons between the northern and southern hemispheres, it is believed that
the humpbacks of the two never meet, thus there are no "inter-marriages"
between the two groups. In the northern Pacific, three
different populations of humpbacks can be distinguished. They winter in the waters
off the Mariana Islands north of New Guinea, the Hawaiian Islands and along the
north coast of Mexico, respectively. At 11 or 12 meters
in length (33-36 feet), they reach sexual maturity. The reproductive period stretches
throughout the winter season, and pregnancy lasts one year, at the end of which
the female will deliver its young, measuring 4.5-5 meters (13-15 feet) in length.
She can give birth approximately every 2 or 3 years. The
humpbacks use a very particular strategy to obtain food. When they detect a bank
of "krill" (crustaceans that resemble shrimp), they dive under it and
begin to "round them up", creating a curtain of bubbles that forces
the krill to concentrate in the middle of it. Once the krill have been rounded
up, the whale will initiate a vertiginous rise towards the surface, jaws wide
open, thus capturing huge quantities of krill in one movement.  They
consume 1 to 1-1/2 tons of food per day. If we consider that each "mouthful"
can capture 1.5-2 grams (less than one ounce) of food per cubic meter (yard),
this means that they have to filter about 1 million cubic yards of water through
their baleens to get their daily quota of nutrition.
This
whale is famous throughout the world for its "song", resulting in many
recordings and TV specials. Such acoustical expressions are related to all the
behavioral facets of the species. In fact, it has been discovered that songs vary
according to populations, seasons of the year and time. Thus it was concluded
that the sounds aren't just simple calls, but rather an articulated "dialect",
complete with links, pauses and stops. In 1996, the Whaling
Committee imposed a total ban due to the near-extinction because of commercial
whaling. Today, there are no more than 5,000 specimens world-wide, about 1,000
of which are believed to live in the Pacific. Known around
the world as a promoter of protection of marine mammals, Mexico set strict limits
on the capture of this specially-protected cetacean. It is thus contributing in
an exceptional manner to the promotion of its recuperation and conservation for
future generations. cupul@pvmirror.com Archives
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