The blue whale is the largest of all whales. The average length of an adult blue whale is 79 to 88 feet and the average weight is 130 to 150 tons. Blue whales are blue to blue-gray in color but may sometimes appear to have a faint yellow skin color caused by the many microorganisms that accumulate on their bodies. They prefer cold waters and open seas.
Blue whales were abundant in nearly all the oceans on Earth until the beginning of the 20th century. For over a century, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide.
Due to their enormous size, power and speed, adult blue whales have virtually no natural predators. There is one documented case in National Geographic Magazine of a blue whale being attacked by orcas off the Baja California peninsula; although the orcas were unable to kill the animal outright during their attack, the blue whale sustained serious wounds and probably died as a result shortly after the attack.
Blue whales may be wounded, sometimes fatally, after colliding with ocean vessels, as well as becoming trapped or entangled in fishing gear. Human threats to the potential recovery of blue whale populations include accumulation of polychlorinated biphenyl (PCB) chemicals within the whale’s body.
The blue whale’s migratory patterns are based on ocean temperature but, with global warming causing glaciers and permafrost to melt rapidly, any disruption in the circulation of warm and cold water around the world could have an effect on their migration.
Their diet is mostly krill (small shrimp-like crustaceans) which they sieve from the water using baleen plates lining their mouths. A single blue whale can consume several tons of krill every day. A change in ocean temperature would also affect the blue whale’s food supply. The warming trend and decreased salinity levels would cause a significant shift in krill location and abundance!
The blue whale could be the largest animal that has ever lived on land or water. The biggest land animal, the African elephant, could stand on the blue whale’s tongue! Even the biggest dinosaur that ever lived was only about one-fourth the size of a blue whale!