The Atlantic blue whale, a distinct population of Balaenoptera musculus, is the largest animal to have ever existed on Earth. These immense creatures navigate the ocean, their scale dwarfing even the largest dinosaurs. Individuals can reach lengths of up to 90 feet, with females being larger than males. A newborn calf, at about 23 feet long, is larger than a full-grown giraffe is tall. This population is genetically separate from its counterparts in the Pacific and Southern Oceans.
Anatomy and Diet
The blue whale’s body is long, slender, and streamlined. Its skin is a mottled blue-gray that appears light blue underwater, giving the animal its name. This mottling pattern is unique to each individual, allowing researchers to identify them. A prominent ridge runs from its blowhole to its upper jaw, and its U-shaped head makes up about a quarter of its body length.
A series of 55 to 90 throat grooves, or pleats, extend from its chin to its navel. These grooves allow the whale’s throat to expand dramatically to support its diet of tiny shrimp-like crustaceans called krill. As baleen whales, they have plates hanging from the roof of their mouth that act as a massive filtration system.
To eat, a blue whale lunge-feeds by accelerating and opening its mouth to engulf enormous volumes of water and krill. It then closes its mouth and uses its tongue to push the water out through the baleen plates, trapping the krill inside. An adult blue whale can consume up to 6 tons of krill in a single day during the peak feeding season.
Atlantic Range and Migration
The Atlantic blue whale population ranges from the subtropics to the frigid feeding areas of the far North Atlantic, with movements driven by food availability. During summer, they are most frequently found in krill-rich waters around Iceland, Greenland, Newfoundland, and the Gulf of St. Lawrence.
As winter approaches, the whales migrate to more temperate and subtropical waters for breeding and calving, though their precise routes are not fully understood. During this journey and the breeding season, they eat very little, relying on blubber reserves built up during the summer.
Vocalization and Social Behavior
Blue whales produce some of the loudest, lowest-frequency sounds in the animal kingdom, often below the range of human hearing. These infrasonic calls can reach 188 decibels, louder than a jet engine, allowing communication over hundreds of kilometers. This long-distance ability is important for a species that is often solitary.
The calls are thought to be for mating, navigation, and maintaining contact. Despite this, blue whales are not highly social and are most commonly observed alone or in pairs. The most stable bond is between a mother and her calf. While congregations may occur in areas with abundant food, they are temporary gatherings, not structured pods.
Population and Conservation Threats
Industrial whaling in the 20th century nearly drove the Atlantic blue whale to extinction. Although commercial whaling is now banned and the species is protected, its recovery is slow. The current population is a small fraction of its pre-whaling size, but there are signs of a slow increase.
Modern threats continue to impede their recovery. One danger is ship strikes, as their size and tendency to surface for air make them vulnerable to collisions with large vessels in busy shipping lanes. Entanglement in fishing gear is another cause of injury and mortality, as whales can become caught in ropes and nets, leading to drowning, starvation, or severe wounds. Ocean noise pollution from shipping and industrial activities is also a concern, as it can interfere with their ability to communicate, navigate, and find food.