Whale: What It Is and How It Lives

A whale isn’t a big fish. It’s a mammal, and it carries one or two blowholes on the crown of its head for breathing, while dolphins have only one, according to americanoceans.org. Over the course of evolution the cetacean group returned to the water after descending from land-dwelling ancestors, a path that Darwin’s theory of evolution helps frame: natural selection doesn’t follow a fixed blueprint, it gradually adapts a lineage to the environment it lives in.

Within the cetacean group there are two biological branches with very different mouths. According to NOAA Fisheries, baleen whales use baleen plates to strain small prey, such as krill, out of the water; toothed whales instead have teeth and hunt fish, squid, and other marine mammals one at a time. The distinction matters more than the common name: the orca, popularly called the “killer whale,” actually belongs to the dolphin family (Delphinidae), of which it’s the largest member, a toothed whale, not a baleen whale.

The title of biggest animal in the world still goes to a baleen whale. According to NOAA Fisheries, blue whales in the North Atlantic and North Pacific reach about 27 meters and exceed 45 tons, while Antarctic individuals reach about 33.5 meters and exceed 149 tons: no other animal has ever come close to that size. The sperm whale, a toothed whale, measures between about 12 meters (females) and 16 meters (males) and weighs between about 14 and 41 tons: the bulkiest of all known toothed whales, though still far smaller than the blue whale.

Blue whales live in every ocean except the Arctic, according to NOAA Fisheries.

Practical example: picture a blue whale and a sperm whale side by side: 33 meters against 16 is more than double, yet both count among the ocean’s giants. The confusion comes from comparing two different things, the largest of all cetaceans and the largest toothed cetacean, not the same record.

The blue whale feeds almost exclusively on krill, with fish and copepods as occasional extras, according to NOAA Fisheries. It approaches krill swarms with its mouth wide open, then expands the pleats in its throat and closes its mouth around the prey: the largest individuals can eat up to about 5.4 tons a day. The humpback whale, another baleen whale, uses a different technique, group coordinated bubble net feeding: curtains of air bubbles that concentrate prey into a tighter spot, easier to swallow in one go.

Toothed whales hunt very differently. The sperm whale chases prey during deep dives that typically reach about 600 meters and can last up to 45 minutes, according to NOAA Fisheries. The orca has the most varied diet of any cetacean: “transient” populations feed mainly on marine mammals and squid, while “resident” populations rely mostly on salmon, and it often hunts in teams, working together like a pack of wolves. It lives in groups called pods, built around maternal bonds and seen traveling together more than half the time. The social behavior of marine mammals stays a field of study on its own across many species, from orcas to otters, each with its own adaptations to life in the water.

The blue whale spends summer feeding in polar waters, then makes long migrations toward equatorial waters as winter sets in, according to NOAA Fisheries. Some humpback whale populations migrate roughly 8,000 km between tropical breeding grounds and the colder, richer waters where they feed. During these journeys the blue whale typically swims at around 8 km/h, but can speed up past 32 km/h in short bursts.

Whales also communicate across great distances. The blue whale is among the loudest animals on the planet and produces pulses, moans, and groans that, under favorable ocean conditions, are thought to be heard by other whales up to about 1,600 km away, according to NOAA Fisheries. The humpback whale is best known for its song and for surface behaviors such as breaching, leaping out of the water, and slapping its pectoral fins and tail.

Estimated lifespan is about 80-90 years for both the blue whale and the humpback whale, according to NOAA Fisheries; the sperm whale’s can reach about 60 years. Conservation status varies by species. NOAA Fisheries lists the blue whale as endangered everywhere it lives: the individuals left are only a remnant of the numbers that existed before commercial hunting expanded in the early 1900s, even though populations are growing worldwide. In 2016, four of the humpback whale’s 14 distinct population segments were still protected as endangered and one as threatened. The orca, for its part, has a global population estimated at about 50,000 individuals according to NOAA Fisheries, though some local populations are tiny: a July 2025 census counted only 74 orcas in the “Southern Resident” population.

This Recap doesn’t go into species- and place-specific detail, such as the narwhal, the bowhead whale, or the Pelagos Sanctuary in the Mediterranean: those deserve a Recap of their own. The whale, like every mammal, is built from the same basic biological units: the Recap on the cell tells that story.