The fin whale, known scientifically as Balaenoptera physalus, is the second-largest animal on Earth, surpassed only by the blue whale. Its immense size is a key characteristic, highlighting its significant presence in marine ecosystems. Understanding the fin whale’s physical dimensions provides insight into the adaptations necessary for life at such a grand scale.
Understanding Fin Whale Size
Adult fin whales typically average a mass of 40 to 50 metric tons (45 to 55 short tons), with some individuals reaching 70 to 80 metric tons (77 to 88 short tons). A maximum recorded weight for the species is 120 metric tons (130 short tons). Adult males generally measure around 21 meters (69 feet), while females are slightly longer, averaging 22 meters (72 feet). The longest recorded fin whale reached 26 to 27 meters (85 to 89 feet).
An adult fin whale can weigh as much as 10 large elephants. Newborn calves weigh 1,600 to 2,700 kilograms (3,500 to 6,000 pounds) and measure 5.5 to 6.5 meters (18 to 21 feet) at birth. This initial size allows them to grow rapidly, reaching physical maturity around 25 to 30 years of age.
Fueling Their Immense Size
Fin whales sustain their enormous mass by eating small schooling fish, such as herring and capelin, along with various species of krill and copepods. They are filter feeders, having 260 to 480 baleen plates on each side of their mouths that act like a sieve. These keratin plates can be up to 76 centimeters (30 inches) long and fray into fine hairs near the tongue.
Their feeding method, known as lunge-feeding, involves rapidly accelerating with open mouths into dense patches of prey. During a lunge, the fin whale’s throat region, which has 50 to 100 ventral grooves, expands dramatically to engulf a large volume of water and prey, sometimes exceeding the whale’s own body volume. The whale then expels the water through its baleen plates, trapping the food inside. A single fin whale can consume up to 1,800 to 2,800 kilograms (2 to 2.8 tons) of food per day during feeding seasons, spending around three hours daily foraging.
Variations in Fin Whale Mass
Several factors contribute to variations in individual fin whale mass. Age plays a significant role, as calves grow from 1,600 kg at birth to reach their full adult size, which can take 25 to 30 years. Sex also influences size, with adult female fin whales generally being 5-10% longer and heavier than males. Northern Hemisphere females, for example, average 50.5 metric tons, while males average 38.5 metric tons.
Geographical location introduces further variations, with fin whales in the Southern Hemisphere often being larger than those in the Northern Hemisphere. This difference may be linked to regional prey availability and distinct population characteristics. Seasonal changes also impact a whale’s mass, as they feed heavily in colder, high-latitude waters during spring and summer to build blubber reserves. They then migrate to warmer waters in winter where food is scarcer and they may fast.
Ecological Importance of Their Biomass
The immense biomass of fin whales contributes significantly to marine ecosystems, playing a role in nutrient cycling. As these large filter feeders consume vast quantities of krill and small fish in nutrient-rich feeding grounds, they concentrate these nutrients within their bodies. Through vertical movements in the water column and defecation near the surface, whales release nutrients like iron and nitrogen, which are often scarce in surface waters. This “whale pump” mechanism can stimulate the growth of phytoplankton, the base of the marine food web.
Fin whales also contribute to carbon sequestration. Their large bodies store carbon throughout their long lifespans, which can exceed 90 years. When a fin whale dies, its carcass sinks to the seafloor, transporting this stored carbon to the deep ocean, effectively removing it from the atmosphere for extended periods. This process enhances the biological carbon pump, a natural system that transfers carbon from the atmosphere to the deep sea. Fin whales are also apex predators in the food web, influencing prey populations and contributing to marine environmental balance.