BLUE WHALE
Balaenoptera musculus (Linnaeus 1758)

Order Cetacea : Family Balaenopteridae

DESCRIPTOIN. 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 plates to each side; snout broad and U-shaped. Blue whales commonly reach lengths of 24–26 m and weigh approximately 100 metric tons. Exceptional individuals may attain 30 m and weigh 150 metric tons.

DISTRIBUTION. 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 identifications have been questioned, however, and the occurrence of the blue whale in the Gulf of Mexico has been considered problematic. More recently, however, a blue whale stranded at Veracruz, Mexico, south of the Texas coast, and it appears to represent a valid record. The worldwide population is estimated at only 11,000–12,000 animals, with the North Atlantic population numbering in the low hundreds.

SUBSPECIES. Balaenoptera m. musculus.

HABITS. Spring and summer find 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. The same trend is exhibited by southern hemisphere blue whales, although feeding grounds are in the Antarctic. As the seasons are reversed in 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 toward northern waters. Small, shrimplike crustaceans known as krill predominate in the diet, and tremendous amounts of them are required to sustain a single whale. An adult blue whale must consume about 3–5 metric tons 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 7 m in length and weighs 2–3 metric tons. The baby whale nurses for about 8 months, and during that time it gains 90 kg per day, or 3.75 kg per hour. Sexual maturity is reached at 5–6 years, and the life span is unknown but is certainly greater than 50 years for both females and males.

POPULATION STATUS. Extralimital; rare; strandings. Blue whales probably occur only accidentally in the Gulf of Mexico, and they remain one of the rarest cetaceans known from these waters. The only known stranding in Texas occurred in 1940.

CONSERVATION STATUS. Despite their protected status, blue whale stocks have yet to show an increase in numbers over the past decade, and the USFWS and the IUCN list them as endangered. According to the IUCN, the total population has been depleted by at least 70%, and possibly as much as 90%, over the last three generations. This whale is not included on the TPWD list of threatened or endangered species.

 

From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.