||The Mammals of Texas -
Cetacea : Family
Balaenopteridae : Balaenoptera musculus (Linnaeus)
Description. Largest of the whales;
upperparts slate gray with bluish cast, darker on head,
lips, and throat; paler on sides; underparts often
yellowish, sometimes spotted with white; dorsal fin
small, located posterior to vent; pectoral fin small,
about one-tenth of total length; commissure of mouth
nearly straight, except for downward curve near corner;
grooves on underparts numerous and extending posteriorly
past navel; whalebone black, broad basally, short (60-80
cm), and averaging 370 to each side; snout broad and
U-shaped. External measurements of one reported by
Scammon: length, 29 m; girth, 12 m; length of jawbone,
6.4 m. Estimated weight, up to 100 metric tons.
Distribution in Texas. Blue
whales occur in all oceans of the world. There are only
two records from the Gulf of Mexico; one stranded near
Sabine Pass, Louisiana, in 1924 and one stranded on the
Texas coast between Freeport and San Luis Pass in 1940.
Both of these identifications have been questioned,
however, and the occurrence of the blue whale in the Gulf
of Mexico is problematical. The current worldwide
population is only 11,000-12,000, with the current North
Atlantic population numbering 100-1,500 animals. Blue
whales are classified as "endangered."
Habits. Spring and summer finds
northern hemisphere blue whales migrating northward to
arctic feeding grounds. In fall and winter the whales
move back to temperate waters where mating and
parturition take place. This trend is also exhibited by
southern hemisphere blue whales although feeding grounds
are in the Antarctic. As the seasons are reversed between
the two hemispheres, northern and southern blue whales do
not interbreed in temperate and equatorial waters.
Feeding occurs mainly in higher
latitudes but is also common during migration. In the
North Pacific, for example, blue whales stop to feed off
California every fall of the year, on their way towards
northern waters. Small, shrimp-like crustaceans known as
"krill" predominate in the diet, tremendous
amounts of which are required to sustain a single whale.
An adult blue whale must consume about 3,000-5,000 kg of
krill daily to meet its energy requirements.
Female blue whales give birth to a
single calf in temperate or equatorial waters during the
winter months. Gestation is about 11 months and females
bear young every other year. The birth of a blue whale
has never been observed, but records from past whaling
activities indicate that a newborn blue whale is about 8
m in length and weighs 2-3 metric tons. The baby whale
nurses for about 8 months and during this time gains 90
kg per day, or 3.75 kg per hour! Sexual maturity
is reached at 5-6 years and the lifespan is unknown.
Illustration credit: Pieter