You may know that blue whales are the largest animals to ever live, and that centuries of human hunting decimated whale populations around the world (though many have recovered since a 1986 global moratorium on commercial whaling was enacted). But we still have a lot to learn about these beasts of the deep. In 2015, Mental Floss spoke with Dr. Joy Reidenberg, a comparative anatomist and contributor to the PBS/BBC series Inside Nature's Giants, about what makes whales so fascinating.
1. The ancient Greeks thought whales were sea monsters.
Whales belong to the infraorder Cetacea, which also includes dolphins and porpoises. It comes from the Greek word keto; in Greek mythology, Keto was the goddess of sea monsters, and when the Greeks saw the cresting backs of a group of whales, they believed them to be all part of one giant sea serpent.
2. Whales have an herbivorous ancestor.
The closest living relative to whales is the hippo, another aquatic mammal (though not to the same degree, of course). But they’re descended from a long line of four-legged animals—including the remarkable-looking ambulocetus, or “walking whale”—a mammal that resembled a crocodile in shape. Although all whales today are carnivores, according to Reidenberg, “They derive from an ancestor that’s not a carnivore. Their common ancestor was an animal that’s very much like modern-day artiodactyls, i.e., ruminant animals that chew their cud—cows, deer, sheep, giraffe.”
3. Some toothed whales suck up their food.
Whales are classified into two categories: Those with teeth and those with baleen. Odontoceti ("toothed whales") contain two sub-categories. As Reidenberg explained, some have “a tooth structure that’s not all that different from what you see in a crocodile or an alligator—lots of teeth, all the same shape, all lined up, all roughly the same size, and they just snap those teeth together to grab the fish.”
But other species, like the sperm whale, have teeth only on their bottom jaw, which makes it all but impossible to grab their food. Instead, they suck up their prey. “When they want to eat something like a squid, they get really close to the squid and they suddenly depress a bone in their throat called the hyoid," Reidenberg said in 2015. "It pulls the back of the tongue inwards and creates a negative pressure in the mouth and that sucks the prey with the water into the mouth. They then squeeze the water back out and swallow the prey. They’re like vacuum cleaners.”
4. Baleen is not a type of tooth.
The whales that have baleen are known as Mysticeti—Greek for “mustached whales.” Although they have baleen instead of teeth, it’s not because the teeth have evolved into baleen or even fully replaced teeth. In fact, “as a fetus they have both and just never fully develop the teeth. They only develop the baleen,” Reidenberg said. The baleen is made of keratin, like your hair or finger nails, and grew out of the same ridges that are also in human mouths. “If you feel the top of your mouth, it’s kind of bumpy. That’s what becomes baleen in baleen whales,” Reidenberg says.
5. Some baleen whales can expand their throats when feeding.
Just like there are two types of odontocetes, there are also two types of mysticetes. Some baleen whales, such as right whales, are constantly taking in water and filtering it out the back of their mouth. Tiny prey collects on their vast baleen plates, which they then lick off for food. Others, like humpbacks and blue whales, are “lunge feeders” who take in huge gulps of water that they then push out through smaller baleen to sieve for food. Some whales even expand their throats like a pelican to create a bowl out of their lower jaw, which is equipped with accordion pleats that allow for huge expansion. According to Reidenberg, “they take in a volume of water that’s pretty close to the volume of the whole animal itself, so they can almost fit another whale in their throat."
6. Baleen whales come in different colors.
Some whales are blonds and some whales are brunettes, but what’s more interesting is that some whales have incredibly strategic streaks. Many whales rely on counter-shading, with dark tops and light bellies, for camouflage. This way, fish looking down at the dark depths of the ocean will be less likely to notice the dark top of a whale, while fish underneath the animal will be less likely to notice a white belly as it blends in with the bright sky. The exception is fin whales, which turn on their sides to feed. Their coloration differs side to side and not top to bottom.
7. Eating is not a year-round activity for whales.
You might think that such huge animals—the average weight of a blue whale hovers around 420,000 pounds—subsisting on such tiny prey would have to eat constantly. But in fact, whales go about half the year eating nothing at all. They feast in nutrient-rich cold water near the poles, but then migrate closer to the equator for mating and don’t eat during that season. All that gorgeous, clear water around the middle of the globe is transparent because it lacks nutrients, like krill. Whales prefer to mate and give birth there because of the lack of potential predators.
“They’re not eating the entire time they’re in the south,” Reidenberg says. “This means moms have to nurse a baby or carry pregnancy off the fat that she’s carrying. This is the reason why, most of the time, the bigger whales are actually female, which is backwards from the rest of the mammalian world. She’s got to carry around this enormous backpack of extra fat, all distributed around her body, not only to sustain her but to sustain the calf or the fetus.”
8. You can identify a whale's species by the shape of the vapor coming out of its blowhole.
What you see when a whale spouts out of its blowhole at the surface is not water from the ocean, but rather the condensate from air in its lungs. “They exhale like we sneeze; all of it comes out very suddenly and under high pressure," Reidenberg says. "It’s almost like popping open a soda can. When you pop open a soda can, you see that little mist—that’s kind of what a whale does every time it breathes because it’s under high pressure. Any dissolved fluid in the vapor become droplets.”
And these clouds of droplets take a distinct shape depending on the species of whale. A long, skinny, smokestack-like puff is usually a blue whale or a fin whale. If it’s more heart-shaped, then it’s more likely to be a humpback whale, and if it’s more V-shaped, that’s more likely to be a right whale.
9. Whales no longer have legs, but they still have a pelvis.
It’s not purely a vestige from their land-locked era many eons ago, either. Skeletally speaking, the pelvis reduced to two small bones that are just sort of floating—one on each side of the whale, unattached to the spine. But it’s still functional. For all whales, it serves to support the muscles of the belly. For males, it plays a crucial role as an anchor for the penis.
10. Whale bones are heavier than those of land animals.
Blubber is so buoyant that, on its own, it would make the whales float too much, leaving them stuck at the water’s surface. To counteract this and achieve neutral buoyancy, whales have heavy bones.
Whales modulate the amount of air stored in an extra sac under their larynx to maintain their position in the way. This air reserve is also used to vocalize without exhaling. Whales can recycle the same air past their vocal folds multiple times before having to return to the surface to breathe.
11. Toothed whales make high-frequency sounds; baleen whales make low-frequency sounds.
Toothed whales, including dolphins, rely on the short wavelengths of high-frequency sounds for super-specific echolocation. The way the sound waves bounce off objects allows the whales to detect nearby prey with remarkable accuracy—they can even sense the texture of the fish they’re “looking” at. Baleen whales, on the other hand, make low-frequency sounds with large wavelengths that don’t pick up on those fine details. The benefit is that low frequencies can travel long distances and not degenerate. This allows baleen whales like humpbacks to communicate with one another over huge distances.
12. Whales aren't just highly intelligent—they're emotional, too.
Baby whales are born with exceptionally large heads and big, complex brains, indicating a level of intelligence uncommon within the animal kingdom. They’re not just smart, though. Research from 2006 showed that whales have the same von Economo neurons (also known as spindle neurons) that allow humans to feel complex emotions.
This intelligence and social awareness is what allows humpback whales to coordinate an elaborate feeding method, in which one whale surrounds a school of fish by swimming in a spiral and releasing bubbles that rise up and create a net. The fish fear the bubbles and end up trapped. One whale lets out a feeding call, inciting the pod to swim together through the spiral and scoop up the fish. Other whales, like killer whales, have similarly complex hunting methods.
A version of this story ran in 2015; it has been updated for 2022.