Blue Whale

Description

The blue whale is the largest animal ever known to have existed on Earth, reaching lengths of up to 100 feet and weights of approximately 200 tons. Their bodies are long and slender, with a mottled blue-gray coloration that appears light blue when seen through the water. The underside of the flippers may be lighter in color, and the skin often carries a pattern of small light spots created by diatom communities. Blue whales have a broad, flat, U-shaped head that makes up nearly one-quarter of their total body length, and a prominent dorsal ridge running from the blowhole to the upper lip. Their blow is tall and columnar, reaching heights of 30 feet or more, making them identifiable from great distances.

Habitat & Range

Blue whales are found in all of the world’s oceans, migrating between high-latitude feeding grounds in summer and low-latitude breeding grounds in winter. In the eastern North Pacific, they feed primarily along the coast of California, with significant concentrations observed off the coast of Southern California and in the waters near the Channel Islands from June through October. During winter months, they migrate south toward the Costa Rica Dome and waters off Baja California, Mexico, to breed and calve. The waters off Orange County serve as an important corridor during both the northbound spring migration and the southbound fall migration.

Diet

Blue whales are filter feeders that subsist almost exclusively on krill, particularly species of the genus Euphausia. An adult blue whale can consume up to 4 tons of krill per day during the feeding season. They feed by lunging through dense aggregations of krill with their mouths open, engulfing enormous volumes of water and prey, then filtering the water out through their baleen plates. The baleen plates, numbering between 260 and 400 on each side of the upper jaw, trap the krill inside the mouth. Blue whales typically feed at depths of 100 meters or more during the day and closer to the surface at night, following the vertical migration of their prey.

Behavior

Blue whales are generally solitary or found in pairs, though they may loosely aggregate in areas of high prey density. They are capable of diving to depths of over 300 meters and can remain submerged for up to 20 minutes, though feeding dives are typically shorter. Blue whales produce extremely loud, low-frequency vocalizations that can travel hundreds of miles through the ocean and reach up to 188 decibels, making them the loudest animals on the planet. These calls are thought to serve functions in long-range communication and possibly mate attraction. Despite their massive size, blue whales can reach speeds of up to 20 miles per hour in short bursts when startled or during feeding lunges. Females give birth to a single calf after a gestation period of approximately 10 to 12 months, and calves are nursed for about 6 to 7 months.

Conservation Status

Blue whales are listed as Endangered under both the U.S. Endangered Species Act and the IUCN Red List. Commercial whaling in the 20th century devastated blue whale populations worldwide, reducing them from an estimated pre-whaling population of 200,000 to 350,000 individuals to fewer than 10,000. The eastern North Pacific population, which is the group most commonly seen off the coast of Southern California, has shown signs of recovery and is estimated at approximately 2,000 to 3,000 individuals. Current threats include ship strikes, entanglement in fishing gear, ocean noise pollution that can interfere with their communication, and climate change affecting krill abundance and distribution. The International Whaling Commission has prohibited the hunting of blue whales since 1966.