50 Fun Facts About Marine Mammals

Which thick layer under the skin keeps whales and seals warm in icy seas and helps them float?

Blubber can be more than 30 centimetres thick on the biggest whales and make up as much as half of an animal's body mass at some points in its life.

Which ocean giant, whose heart alone can weigh about 180 kilograms, is the largest animal known ever to have existed?

The blue whale reaches about 30 metres and 200 tonnes, yet it lives almost entirely on tiny shrimp-like animals strained from the sea.

Which Arctic whale carries a long spiral tusk that is really a canine tooth growing out through the upper lip?

The narwhal's tusk fed a medieval belief that it was the horn of the legendary unicorn. Females rarely grow one, and a few males grow two.

Which marine mammal is a keystone species of kelp forests because it eats the spiny urchins that graze them bare?

The sea otter also has the densest fur of any animal, and it is one of the few mammals to use tools, cracking open shells with rocks.

Which Arctic hunter of seals is counted as a marine mammal because it depends so heavily on the ocean?

The polar bear's scientific name, Ursus maritimus, is Latin for 'sea bear'. One study found the bears swimming for an average of 3.4 days at a stretch.

Which mythical creatures did Christopher Columbus report off Hispaniola in 1493, having probably seen manatees?

Mermaids, Columbus wrote, were not as beautiful as painters made them. Sea cows still carry the legend in the name of their order, Sirenia, after the sirens of Greek myth.

Which sense lets dolphins find fish in dark water by sending out clicks and listening for the returning sound?

Echolocation in dolphins sends a focused beam of clicks out through the forehead, and the returning sound is picked up through the lower jaw.

Which black-and-white hunter is, despite the common name, the largest member of the oceanic dolphin family?

The killer whale, or orca, is one of the few animals whose females go through menopause, living for decades afterwards as the heads of their family groups.

DNA evidence shows which large African land mammal is the closest living relative of whales and dolphins?

The hippopotamus shared an ancestor with the whales until about 55 million years ago, which makes hippos closer kin to dolphins than to pigs.

How do dolphins keep surfacing to breathe while asleep, when each breath is a deliberate act?

Half the brain stays awake while the other half sleeps, leaving a dolphin just conscious enough to breathe and to watch for predators.

Which comb-like plates, made of the same keratin as human fingernails, let the largest whales strain food from seawater?

Baleen hangs in rows from the upper jaw in place of teeth. Under the misleading name whalebone, it once stiffened corset stays, collars and parasol ribs.

Which deep-diving giant, the largest toothed predator on Earth, also has the biggest brain of any animal?

The sperm whale carries a brain more than five times heavier than a human's, and its clicks are the loudest sounds made by any animal.

Which shrimp-like crustaceans, swarming in huge numbers off Antarctica, are the main food of filter-feeding whales?

Krill swarms can pack tens of thousands of animals into a single cubic metre, and the Antarctic species alone adds up to hundreds of millions of tonnes.

Which Arctic giant may live for more than 200 years, the longest lifespan known for any mammal?

The bowhead whale is named for its massive skull, which it uses to break up through Arctic ice, and it has the largest mouth of any animal.

Which sea giant is known for the males' long, complex songs and for herding fish inside rings of bubbles?

The humpback whale's bubble nets are counted as a form of tool use, and a single song by a male can run for more than half an hour.

Which white Arctic cetacean is nicknamed the sea canary for its high-pitched squeaks, squeals and clucks?

The beluga whale has no fin on its back, which lets it swim easily beneath sea ice, and its name comes from the Russian word for white.

What is the name for the nostril on top of a whale's head, which moved there from the snout during evolution?

The blowhole is a single opening in toothed whales and a pair in the great filter feeders, and the stale air blown out of it forms the steamy spout.

Which fruit shares its name with the rounded forehead organ that toothed whales use to focus their sound beams?

The melon works like a lens for sound, bending the animal's clicks into a narrow beam aimed wherever the head is pointing.

Which waxy substance, formed in the gut of a deep-diving whale, was long prized by perfume makers?

Ambergris makes a scent last much longer on the skin, though perfumers have mostly replaced it with a synthetic copy.

Which colour do adult Amazon river dolphins, known as botos, take on as years of scrapes wear at the skin?

Pink shows most strongly in males, which pick up more scars from fighting one another. The boto is also the largest of the river dolphins.

Which land giants, along with the little hyraxes, are the closest living relatives of the sea cows?

Elephants share a telling quirk with manatees: both keep replacing their teeth through life, with new ones moving forward from the back of the jaw.

Which marine mammal, the only plant-eater living strictly in the sea, has a fluked tail like a dolphin's?

The dugong grazes on seagrass meadows, and it stands alone because every species of manatee uses fresh water to some degree.

Which giant kelp-eating marine mammal of the Bering Sea was hunted to extinction within 27 years of its 1741 discovery?

Steller's sea cow was first described by Georg Steller while he was shipwrecked on Bering Island, and it was slow and easy for hunters to catch.

Which US state named the manatee its official marine mammal and shelters hundreds each winter in warm spring-fed rivers?

Florida's manatees also crowd around the warm-water outflows of coastal power plants in winter instead of migrating south as they once did.

Unlike fish, whales and dolphins drive themselves forward by beating their horizontal tails in which direction?

Up and down beats of a flat, horizontal fluke push a whale along, whereas a fish sweeps an upright tail fin from one flank to the other.

Which body parts did the land-dwelling ancestors of whales lose, leaving only small hidden bones near the pelvis?

Hind legs vanished as whales took to the sea, while the front limbs turned into flippers used to paddle and steer.

Which Arctic animal's scientific name, Odobenus, means 'tooth-walker' in Greek, after the way it hauls out onto ice?

The walrus really does use its tusks to climb out of the water, and it also uses them to make and keep open breathing holes in the ice.

Which marine mammals have small external ear flaps, long front flippers and the ability to walk on all fours?

Sea lions can pull their back flippers under the body to walk on them, while true seals cannot and must wriggle along on their bellies.

Which Antarctic hunter, an apex predator with massive jaws, catches penguins by lurking at the edge of the ice?

The leopard seal also preys on other seals, and it is the second largest seal in the Antarctic.

Which vast Siberian lake has a seal of its own, found nowhere else and living only in fresh water?

Baikal's seal is one of the smallest true seals, and it lives mainly on the golomyanka, an oily fish found only in the same waters.

Which vast inland sea between Europe and Asia has a small seal of its own, found only in its brackish water?

The Caspian Sea's seal is one of the smallest members of the true seal family, and its numbers have fallen by more than 90% since the start of the 1900s.

Which North Atlantic pinniped nurses its pup for only about four days, the shortest nursing period of any mammal?

The hooded seal pup doubles in size in those few days, and an adult male can inflate a balloon-like sac out of one nostril.

Which US state chose as its official state mammal a monk seal that lives on its shores and nowhere else?

Hawaii's monk seal is one of only two mammals native to the islands and found nowhere else; the other is a bat.

Which tiny cetacean, found only at the northern end of Mexico's Gulf of California, is the smallest of them all?

The vaquita grows to about 1.5 metres at most, and it has been pushed to the brink of extinction by drowning in gillnets set illegally for a fish called the totoaba.

Which North Atlantic ice breeder has pups that wear a fluffy white coat for two to three weeks before moulting to grey?

The harp seal is named for the dark, harp-shaped marking on an adult's back, and Canada has banned the hunting of its white-coated pups since 1987.

Which great migrant travels each year from the Bering and Chukchi seas to the warm lagoons of Mexico's Baja California?

The gray whale grows so trusting in those lagoons that it often swims close enough to boats for visitors to pet it.

Which animal holds the records for the deepest and longest dives of any mammal, nearly 3 km down and over 3 hours?

Cuvier's beaked whale has been tracked to 2,992 metres and on a dive of 222 minutes, yet it usually rests at the surface for only a few minutes between dives.

Which small relatives of dolphins are told apart by flattened, spade-shaped teeth and the lack of a pronounced beak?

Porpoises come in eight living species, all among the smallest of the toothed whales, while a dolphin's teeth are cone-shaped.

Which great Chinese river was home to the baiji, a dolphin declared functionally extinct after a 2006 search found none?

The Yangtze dolphin was revered by local boatmen as a goddess of protection, and it has been called the first dolphin species driven to extinction by humans.

Which species was the title animal of the 1960s television series Flipper, the wild pet of a park warden's sons?

The bottlenose dolphin hero was played by several females, chosen because they are less aggressive than males and carry fewer scars.

Which oxygen-storing protein, packed into the muscles of whales and seals, lets them stay underwater for so long?

Myoglobin holds oxygen more tightly than the hemoglobin in blood, and its pigments are what give red meat its colour.

Which facial feature lets a harbor seal follow the trail left in the water by a fish that swam past minutes earlier?

Whiskers on a seal each carry about ten times as many nerve fibres as a rat's, and they can even reveal the size of the fish that left the trail.

What happens to a seal's heartbeat on a long dive, as part of a reflex that saves oxygen for the vital organs?

It slows sharply, from about 125 beats a minute to as few as 10, while blood is steered away from the limbs toward the organs that need it most.

Which individually distinctive calls do young dolphins learn and then use to announce who they are, rather like names?

Signature whistles can be borrowed: a dolphin will repeat another's back to it to address that one animal, much as people call each other by name.

Which family of whales, including the fin and minke, has pleated throats that balloon out as they gulp water?

Rorquals take their name from a Norwegian word, and their lunge feeding has been described as the largest biomechanical event on Earth.

Which term describes a whale leaping so that much of its body clears the water before crashing back down?

Breaching may help knock parasites off the skin, and the loud smack on landing may also stun or scare prey.

Which folk art did whalers practise in their spare time by engraving pictures on whale teeth and bones?

Scrimshaw first meant the making of shipboard tools and only later the artwork, and much of the original work is now held by museums.

Which classic experiment in self-awareness did two dolphins pass by twisting to inspect marks on their bodies?

The mirror test showed the dolphins circling their heads and peering closely at the marked spots, behaviour seen in only a handful of species such as the great apes.

Which branch of the American military trains dolphins at a base in San Diego to find and mark underwater mines?

The US Navy says its dolphins helped to find more than 100 mines and underwater booby traps at the Iraqi port of Umm Qasr.

Which sacred Indian river gives its name to a nearly blind dolphin that India has declared its National Aquatic Animal?

The Ganges dolphin has tiny eyes with no lens, so it finds its way and its prey in the murky water by sound alone.