10 incredible facts about the largest animal on Earth – the blue whale

While only a fraction remains of the number of blue whales that once roamed the seas, their numbers are on the rise.
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Blue Whale swimming
Blue Whale


The blue whale, or Balaenoptera musculus, to give them their scientific name, is the largest animal on Earth, inspiring awe and wonder with its size and surprising gentleness. There are five recognized sub-species of blue whales: the Northern blue whale, the Antarctic blue whale (the largest of the species), the Northern Indian Ocean blue whale, the pygmy blue whale, and the Chilean blue whale. Blue whales can be found in all major oceans except the Arctic.

Blue whales are usually found far offshore and migrate seasonally to breeding and feeding grounds. However, they are most commonly seen in the Gulf of California in Mexico, along the California coast, in the Gulf of St. Lawrence in Canada, and off Sri Lanka.

Today, only a fraction remains of the number of blue whales that once roamed the seas. This is due to hunting, as the whale’s oil was once highly prized, injuries from entanglements in commercial fishing gear, and disruption from shipping. Blue whales have been protected from hunting since 1966, and today the populations of some species appear to be slowly recovering. The species is still listed as endangered on the IUCN Red List, and the Antarctic sub-species is listed as critically endangered – its population is thought to be at less than 1% of its pre-whaling size.

Ten amazing facts about the blue whale

10 incredible facts about the largest animal on Earth – the blue whale
Blue Whale

1. The blue whale is the largest animal to have ever lived

And yes, that includes the dinosaurs. The largest blue whale ever recorded weighed around 200 tons and was 100 feet long (33 meters). That’s as long as three school buses from end to end. As you would expect, their organs are also enormous – their arteries are large enough for a child to crawl through, and the blue whale’s heart is the size of a small car (but weighs much less, at around 400 pounds). Their tongue alone can weigh as much as an elephant. However, the blue whale's brain is much smaller, at around 12 pounds – although that still makes it one of the largest animal brains.

2. The blue whale is a baleen whale

This means they have fringed plates of a material called baleen instead of teeth. Baleen is made of keratin, the same protein that makes up your fingernails and hair. Baleen whales eat krill, a tiny aquatic crustacean resembling shrimp. At peak feeding season, a blue whale may consume up to 40 million krill daily, or around 8,000 pounds. The whales feed by gulping in huge mouthfuls of water; their massive tongue then forces the water out through the overlapping baleen plates, leaving the krill behind to be swallowed.

3. Like all whales, the blue whale evolved from a four-legged land mammal that lived around 48 million years ago

Their ancient ancestor, dubbed Pakicetus, was only around 1.8 meters long. After moving into the oceans, the toothed whales evolved filter feeding and grew larger as they adapted to the increased abundance of food. This process accelerated after a rise in ocean upwelling, which occurred sometime around five million years ago and resulted in a great abundance of krill. The enormous size of the blue whale may be a result of their specializing in lunge feeding – evolving huge mouths and bodies to enable them to capture more krill than other species.

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4. Blue whales have an amazing lung capacity

Their lungs can hold around 5,000 liters of air (humans can hold around 6 liters), and their exhalation speed can reach around 372 miles per hour (600 kph). The whales can remain underwater for up to an hour, which is due to their ability to store oxygen in their red blood cells.

10 incredible facts about the largest animal on Earth – the blue whale
Blue whale surfacing

5. Blue whales are some of the loudest animals on the planet

Their vocalizations include a series of pulses and sounds like groans and moans. These sounds are too low for humans to hear – as they can make calls at just 14Hz in frequency. Because low-frequency sounds travel further with less scattering, distortion, and transmission loss, it is thought that blue whales can communicate with each other over enormous distances – as much as 1,000 miles away. Deep underwater, the whales also use these calls like sonar by listening to the echoes of their calls as they bounce off ocean shelves, sea mounts, and coastlines, creating a mental map of the ocean and allowing them to navigate in the lightless depths.

6. They grow fast and live long

Blue whales have a gestation period of around a year, and the calves are born already weighing up to 3 tons and about 25 feet in length – making them among the world’s largest animals right from birth. The calves nurse for around eight months to a year before they are weaned, gaining as much as 200 pounds a day over this time. Whale milk is very thick and has a 30-40% fat content. Blue whales are also among the longest-lived animals. Researchers gauge a blue whale's age by counting the layers of waxlike earplugs in deceased whales. The oldest whale found using this method was 110 years old, and the average lifespan for a blue whale is thought to be around 80 to 90 years.

7. They breathe through the top of the head

Like other cetaceans, blue whales don’t breathe out of their mouths or from their nose in front of their face but from a blowhole on top of their head. In fact, blue whales have two blowholes. The location of the blowholes on the top of their head allows the whales to take breaths while exposing only the top of their heads to the air. After each breath, strong muscles seal the blowhole tightly to keep water from getting into the whale's lungs.

8. Blue whales can tell other whales apart

Each blue whale has a unique marking that distinguishes it from other blue whales. In fact, each blue whale’s skin markings are unique, a bit like fingerprints. Researchers use these to identify individual whales and to learn more about the whales’ ecology, population, life span, and migration paths. Researchers have built up catalogs of individual whales, which are also studied by attaching satellite tags to track their movements.

9. Sleeping while awake – sort of

Like other marine mammals, blue whales spend their entire lives at sea. So, how do they sleep without drowning? Researchers have found that whales use different strategies for this. In the first weeks of life, the calves lack the body fat or blubber to allow them to float easily. At the same time, they need a lot of sleep. To sleep and rest, the young whales stay in their mothers’ slipstreams and are pulled along. This is called echelon swimming. During this time, the mother cannot stop swimming, or the newborn will sink. To rest, whale mothers and adult whales use a different strategy. Whales are conscious breathers; that is, they need to consciously make the decision to breathe. When sleeping, they shut down only one-half of their brain at a time. The ‘awake’ half remembers to surface and breathe, and the eye connected to the awake hemisphere stays open to check for danger.

10 incredible facts about the largest animal on Earth – the blue whale
Baby blue whale and its mother

10. Humans are their main predators

The only known natural predator of blue whales is the killer whale. But since the 19th century, the main predator of the blue whale has been humans. As mentioned above, whales were widely hunted for their oil, especially in the early 20th century. Nearly 30,000 whales were killed in 1930-31 alone. The global population of blue whales plummeted to a tiny fraction of pre-whaling numbers until 1966, when they became protected from hunting by the International Whaling Commission (IWC). However, this did not end humans' role in decimating the blue whale population. Although reports of lethal entanglements in commercial fishing gear are rare, many blue whales have been found carrying scarring consistent with fishing gear interaction. Commercial harvesting of krill – the whale’s main food source, and the effects of climate change are also having an effect on blue whale numbers. Ship strike is another risk to blue whales, especially in areas where their habitat overlaps with shipping lanes. The noise from ships is also thought to have the ability to disrupt some of the whales’ signals, perhaps affecting their ability to navigate and find a mate.