Whale

• 1. Introduction

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  Whales are the largest animals that have ever existed on Earth. The blue whale stretches to 29.9 metres and weighs 190 tonnes, a creature so vast that its lungs alone hold about 5,000 litres of air. Yet despite this oceanic immensity, whales are not fish. They are warm-blooded mammals descended from land-dwellers, animals that once walked on legs and only later returned to the sea. How does a creature that breathed air on land end up ruling the open ocean? What turned a hoofed, four-legged animal into the planet's most powerful predator? And why, after millions of years of evolution, are some species now teetering on the edge of extinction? These are the questions at the centre of the whale's story.

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• 2. From Land to Sea

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  Whales are related to the Indohyus, an extinct chevrotain-like ungulate from which they split approximately 48 million years ago. Primitive cetaceans, known as archaeocetes, first entered the sea around 49 million years ago, and they became fully aquatic between 5 and 10 million years after that. What makes an archaeocete identifiable is the presence of features exclusive to cetaceans alongside traits no longer found in modern whales, such as visible legs or asymmetrical teeth.

  The transformation happened gradually, body part by body part. Around 49 million years ago, Ambulocetus developed a hearing system that channelled vibrations through the jaw to the earbone. By around 43 million years ago, Protocetus had acquired a streamlined body and tail flukes. Then, around 35 million years ago, Basilosaurus evolved modified forelimbs that had become flippers, while the hind limbs began their long process of shrinking away. By 34 million years ago, the first toothed whales and baleen whales had appeared, and hind limbs had effectively vanished.

  This evolutionary path produced some striking parallels with unrelated animals. Whale body shapes converge on the same torpedo form as fish. Toothed whales developed echolocation, the same acoustic hunting tool used by bats. And rorqual whales evolved jaw mechanics that work much like those of pelicans, allowing them to engulf enormous quantities of water and prey in a single lunge.

  Today, the hippopotamus is the closest living relative of all cetaceans. A semi-aquatic ancestor split from other even-toed ungulates around 60 million years ago, and around 40 million years ago that lineage divided again, one branch heading toward the sea to become whales, the other eventually becoming the anthracotheres. Nearly all anthracotheres died out at the close of the Pleistocene, about 2.5 million years ago, leaving the hippopotamus as the sole survivor of that entire branch.

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• 3. Two Bodies, One Order

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  Around 34 million years ago, whales split into the two great groups that define them today. Baleen whales, the Mysticeti, filter enormous quantities of krill and plankton through plates of keratin. Toothed whales, the Odontocetes, chase fish and squid with conical teeth adapted for gripping slippery prey.

  Baleen whales carry heads so large they can constitute up to 40 percent of total body mass. Throat pleats allow their mouths to expand to extraordinary sizes, taking in vast mouthfuls of water that are then pressed through the baleen, which acts as a sieve. The blue whale feeds almost exclusively on krill. The minke whale concentrates on schooling fish. The grey whale forages on bottom-dwelling invertebrates.

  Toothed whales operate through sound. An organ called the melon, composed of fat and housed in a distinctive depression in the skull, projects high-frequency clicks outward. The returning echoes give toothed whales a precise acoustic picture of the water around them. Some can survive even if they are blind, relying entirely on this hearing. The sperm whale, the largest toothed predator on Earth, can generate up to 20,000 watts of sound, and can dive for up to 90 minutes to chase squid into the deep.

  One anatomical difference runs through every member of both groups. Mysticetes have two blowholes; Odontocetes have one. These modified nostrils, positioned on top of the head, are the mechanism through which whales breathe at the surface, expelling stale air in the characteristic upward spout before drawing in fresh air. Spout shapes differ between species clearly enough to serve as identification markers.

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• 4. Intelligence and Communication

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  Humpback whales produce extended, melodic songs that are among the most complex vocal sequences found in any animal. Toothed whales add their own layer of acoustic sophistication, using high-frequency click trains emitted at intervals of roughly 35-50 milliseconds for echolocation, while also producing narrow-band whistles for communication and contact calls. Captive whales have been recorded mimicking human speech, a behaviour that scientists interpret as a strong desire to communicate across species, given how different whale vocal anatomy is from a human larynx.

  The intelligence underlying this communication runs deep. Whales teach, learn, cooperate, plan, and grieve. Many species carry elongated spindle neurons in the neocortex, the same cells that in humans are linked to social conduct, emotional regulation, and theory of mind. Whale spindle neurons occupy regions of the brain that are anatomically equivalent to where they appear in the human brain.

  Sperm whales carry the largest brain mass of any animal that has ever lived, averaging 8,000 cubic centimetres and 7.8 kilograms in mature males, compared to an average of 1,450 cubic centimetres for a mature human male. In belugas and narwhals, the ratio of brain mass to body mass is second only to humans among all mammals.

  Small whales play in ways that are hard to describe as anything but inventive. They blow stable underwater toroidal rings, what researchers call bubble rings, by either puffing a burst of air into the water and letting it rise, or by circling repeatedly to create a helical vortex and then injecting air into it. Observers have recorded them biting these rings to shatter them into rising streams of bubbles. The southern right whale off the coasts of Argentina and South Africa can be seen holding its tail fluke above the surface for extended periods in a behaviour called sailing, one that humpback whales replicate as well.

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• 5. The Whale in the Ocean System

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  A 2010 study identified a phenomenon called the whale pump. Whales carry nutrients, particularly nitrogen, from deep water back to the surface when they defecate. Their excrement is liquid and stays near the surface rather than sinking, where phytoplankton feed on the iron and nitrogen it contains. In the Gulf of Maine, this nitrogen input from whales amounts to more than 23,000 metric tonnes per year, exceeding the combined nitrogen contribution of every river that drains into the gulf. Rather than draining nutrients away, whales actively recirculate them.

  When a whale dies, its carcass sinks to the ocean floor and creates an entirely new habitat. Evidence from present-day whale falls and from the fossil record shows that these carcasses support a global diversity of 407 species. Deterioration proceeds in three stages. First, mobile scavengers such as sharks and hagfish strip the soft tissues over a period of months, sometimes lasting two years. Then enrichment opportunists, including crustaceans and polychaetes, colonise the bones and surrounding sediment over several more years. Finally, sulfophilic bacteria break down the bones themselves, releasing hydrogen sulphide that fuels chemoautotrophic organisms, which in turn support mussels, clams, limpets, and sea snails. This final stage can last for decades and on average supports 185 species at each site.

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• 6. Whaling and Its Consequences

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  People from Norway and Japan began hunting whales around 2000 B.C. The Basques joined the hunt as early as the 11th century and were sailing to Newfoundland in the 16th century in search of right whales. By the 18th and 19th centuries, the primary targets were whale oil, used as lamp fuel and lubricant; baleen, shaped into corsets and skirt hoops; and ambergris, valued as a fixative in perfumes. The Netherlands, Japan, and the United States were the most dominant whaling nations of that era.

  By the early 1790s, American and Australian whalers had shifted focus to the South Pacific, hunting sperm whales and right whales. Americans alone caught up to 39,000 right whales during this period. By 1853, the American whaling industry reached its most profitable year, generating US$11 million, equivalent to around US$348 million today.

  The North Atlantic right whale nearly disappeared in the twentieth century, with its population falling to around 450 individuals. Today the total population of that species numbers fewer than 500, and ship strikes are a significant threat. It is believed that up to two thirds of whale-ship collisions go unreported. From 2013 through at least 2023, Chile recorded more fatal whale-ship collisions than any other country in the world.

  The International Whaling Commission placed a moratorium in 1946 that set catch limits for member nations, excluding aboriginal hunters until 2004. As of 2015, aboriginal communities in Alaska were permitted to take 280 bowhead whales per year, among other specific quotas. Whale watching, by contrast, generated US$2.1 billion in tourism revenue annually and employed around 13,000 workers worldwide, while the moratorium-constrained whaling industry brought in approximately US$31 million per year.

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• 7. Whales in Human Culture

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  Petroglyphs carved into a cliff face at Bangudae in South Korea depict 300 animals, roughly a third of which are whales. These carvings, dating from around 7,000 to 3,500 B.C.E., include such anatomical detail as the throat pleats characteristic of rorqual whales, suggesting that the people who made them depended closely on whales and observed them with precision.

  In Vietnam, whales carry a sense of divinity that traces back to the ancient sea-based Champa Kingdom. Funerals are sometimes held for beached whales along the Vietnamese coast. Thai fishermen call Bryde's whales Pla pu, meaning "grandfather fish", and do not hunt them. Across coastal China, Korea, and Vietnam, whale gods were associated with Dragon Kings after the arrival of Buddhism.

  The biblical story of Jonah being swallowed by a great fish appears in both the Qur'an and the Book of Jonah, and is referenced in the New Testament at Matthew 12:40. The scene was depicted repeatedly in medieval art, including on a 12th-century column capital at the abbey church of Mozac in France. The creature described in Job 41:1-34 as the leviathan is widely understood to refer to a whale.

  Herman Melville drew partly on the historical albino sperm whale Mocha Dick when writing Moby Dick. A recording by marine scientists called Song with a Humpback Whale became popular in 1970. That same year, composer Alan Hovhaness released his orchestral work And God Created Great Whales, which incorporates recordings of humpback and bowhead whales. The first beluga ever displayed in captivity appeared at Barnum's Museum in New York City in 1861, and captive belugas were later trained by the United States Navy between 1960 and 1992 to improve sonar detection of underwater objects, while a parallel Soviet program during the Cold War trained belugas for antimining operations in the Arctic.

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