Blue whales get their name from their gray to blue coloration. If conditions are right, diatoms (planktonic photosynthesizers) will build up on their stomachs and make their undersides look yellowish. They are much longer than they are wide and have a small dorsal fin. Whales can sometimes be identified based on the size and shape of their spout. The spout is made of air and condensed water vapor that is released from the whale’s nose, which is on top of its head. The spout of the blue whale can reach more than 30 feet high.
Females are bigger than males. The lengthiest blue whales are 110 feet, but they are more commonly between 70 and 80 feet. Adult blue whales weigh up to 150 tons, which makes them the largest animals to ever live. By comparison, elephants—the largest terrestrial animals—weigh only 4.5 tons.
These whales are distributed globally, including off both coasts of the continental United States. Some populations stay in the same place year-round, but most migrate to the poles in the summer to feed and move back toward the equator in the fall. Blue whales prefer the open ocean, but can sometimes be seen offshore of coastal states.
Despite their huge size, blue whales feed on relatively small prey, primarily tiny shrimp-like animals called krill. Like some other whales, blue whales possess baleen—stiff plates made of hairlike structures—in place of teeth. When they feed, they expel seawater out of their mouths through the baleen, and the krill stay trapped inside. A blue whale can eat up to 7,715 pounds of krill per day. Young blue whales consume 100 to 150 gallons of milk each day from their mother.
Blue whales tend to be more solitary than other whale species. They can, however, sometimes been see them together in small groups of two to four individuals.
Blue whales cruise the ocean at about 20 miles per hour. Their vocalizations can be heard from 1,000 miles away. These vocalizations are thought to be used as communication as well as sonar navigation.
Breeding occurs during the winter months in warm waters near the equator. The gestation period is about a year, during which time adults migrate to the poles to feed. Females return to winter breeding grounds to give birth. Newborn calves are an impressive 23 feet long, and they pack on 200 pounds a day by drinking their mother’s milk. They will reach reproductive maturity at 10 years of age. The whale's estimated lifespan is between 80 and 90 years.
Blue whales are federally listed as endangered. This species was once abundant, but advances in whaling technology made it easier for people to hunt them. With the rise of factory ships, blue whale populations plummeted. They are now protected internationally by a moratorium on whaling, and their numbers are rising. Ship noise, entanglement, and collisions may affect them in areas with high human activity, but occurrences of these events are rare. The effect that climate change will have on blue whales is uncertain.
In addition to being the biggest, blue whales are also one of the loudest animals on Earth. Their songs can reach nearly 200 decibels (louder than a jet engine).
Animal Diversity Web, University of Michigan Museum of Zoology
Defenders of Wildlife
National Marine Life Center
Teaching Science with Whales: A Guide for Teachers, Students, and Parents. Leighton Taylor and Associates: St. Helena, CA 1996.
The IUCN Red List of Threatened Species
U.S. Fish & Wildlife Service
World Animal Foundation
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