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BLUE WHALE
Balaenoptera musculus
meaning of scientific name: mouse-like finned whale (many
think the name was meant as a joke, since blue whales are
so large)
DESCRIPTION: It is difficult to imagine the size of
the blue whale, the largest animal inhabiting the earth. There
are records of individuals over 100 feet (30.5 m) long, but
70-90 feet (23-27 m) is probably average. A good way to visualize
their length is to remember that they are about as long as
three school buses. An average weight for an adult is 200,000
to 300,000 pounds (100-150 tons). Its heart alone is as large
as a small car.
Blue whales are an overall blue-gray color, mottled with light
gray. Cold water diatoms adhere to their skin and sometimes
give their bellies a yellowish tinge, giving the blue whale
its nickname of "sulfur bottom." Blue whales are
long and streamlined. Their dorsal fins are extremely small,
and their pectoral flippers are long and thin. Blue whales
are rorqual whales, a family of baleen whales with pleated
throat grooves that expand when the animal takes in water
while feeding. In blue whales, 55-68 throat grooves extend
from the throat to the navel. Blue whale baleen is black with
over 800 plates.
RANGE/HABITAT: Blue whales have been found in every
ocean of the world. Blue whales swim individually or in small
groups. Pairs are very commonly seen. Approximately 2,000
blue whales live off the California Coast and migrate to Mexico,
and Costa Rica.
BEHAVIOR:
The favorite food of these giants is krill, or shrimp-like
euphausiids, that are up to three inches long. Blue whales
must eat two to four tons of krill a day during the feeding
season. They concentrate on feeding during the polar summers
primarily around the Channel Islands, Monterey Bay, and the
Farallon Islands/Cordell Bank. During the winter months, they
migrate to the warmer waters in Mexico and Costa Rica.
MATING AND BREEDING: Females give birth to calves every
two to three years. They remain pregnant for about one year
before giving birth. When born, the blue whale calf is about
23 feet (7 m) long and weighs 5,000 to 6,000 pounds (2,700
kg). A nursing blue whale mother produces over 50 gallons
(200 liters) of milk a day. The milk contains 35 to 50% milk
fat and allows the calf to gain weight at a rate of up to
10 pounds an hour or over 250 pounds (44 kg) a day! At six
months of age and an average length of over 52 feet (16 m),
the calf is weaned. The blue whale reaches sexual maturity
at around 10 years of age.
STATUS:
The blue whale was too swift and powerful for the 19th
century whalers to hunt, but with the arrival of harpoon cannons,
they became a much sought after species for their large amounts
of blubber. The killing reached a peak in 1931 when 29,649
blue whales were taken. By 1966, blues were so scarce that
the International Whaling Commission declared them protected
throughout the world. Today, there are probably fewer than
15,000 blue whales in the oceans, and they are considered
an endangered species. However, we can see them in the summer
and fall off the central California coast, feeding in such
places as the Gulf of the Farallones and Cordell Bank National
Marine Sanctuaries. The 2,000 blue whales that feed along
the California coast make up the largest concentration of
blue whales in the world.
May be reproduced for scientific and educational purposes
Revised 2/02
Learn more about the following:
Humpback
Whale
Orca/Killer
Whale
Gray Whale
Beluga Whale
Dolphins
and Porpoises
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Blue
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