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  The Mammals of Texas - Online Edition

Blue Whale
Order Cetacea : Family Balaenopteridae : Balaenoptera musculus (Linnaeus)

Blue Whale (Balaenoptera musculus).  Illustration by Pieter A. Folkens.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 A. Folkens.