15 Delightful Facts About Dolphins

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iStock

Dolphins are known for being smart, playful creatures that can learn to perform impressive tricks. But you might not know that dolphins are also champion nappers who have helped the U.S. Navy protect nuclear warheads. We're celebrating National Dolphin Day with these 15 facts about the cute, friendly cetaceans.

1. THEY'RE EXCELLENT NAPPERS.

Since dolphins can't breathe underwater, they need to swim up to the ocean's surface to get air. So how do they sleep without drowning? Essentially, dolphins are champion power nappers. Rather than sleep for several hours at a time, they rest one hemisphere of their brain for 15 to 20 minutes at a time, and they take these "naps" several times each day. By resting one hemisphere of their brain at a time, dolphins can continue swimming, breathing, and watching for predators 24/7.

2. THEY COMMUNICATE WITH CLICKS AND WHISTLES …

dolphins underwater
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Dolphins communicate with one another underwater by making a variety of vocalizations. To find prey and navigate the ocean, they make clicking sounds, and they "speak" to other dolphins by whistling. Dolphins also produce loud burst-pulse sounds when they feel excited or aggressive, such as when they need to scare off a nearby shark. Some female dolphins also produce a burst-pulse to reprimand their offspring, called calves, for bad behavior.

3. … BUT THEIR LANGUAGE REMAINS A MYSTERY.

Although marine scientists have studied and recorded dolphin vocalizations for decades, many aspects of the animals’ language and how they communicate are still unknown. Scientists have not yet broken down the individual units of dolphin sounds, and they're still searching for a Rosetta Stone that links the animals' vocalizations to their behavior. By using new technologies—including algorithms and high-frequency recorders that work underwater—scientists hope to finally unlock the mystery of the dolphin language.

4. THEY USE ECHOLOCATION TO NAVIGATE.

To know where they are in relation to other objects and animals, dolphins use echolocation (a.k.a. biological sonar). After emitting a series of high-pitched clicks, they listen for the echoes to bounce off their surroundings. Based on these echoes, dolphins can judge where they are in space and determine the size and shape of nearby objects. Besides helping dolphins evade predators, echolocation allows them to trap, catch, and eat fish and squid.

5. THEY MAKE FRIENDS WITH OTHER DOLPHINS …

spotted dolphins swimming
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Dolphins are highly social, and scientists are still discovering fascinating details about how the aquatic mammals socialize with one another. In 2015, scientists at Florida Atlantic University's Harbor Branch Oceanographic Institute published research in the Marine Mammal Science journal about the social networks of dolphins. After spending over six years tracking 200 bottlenose dolphins in Florida's Indian River Lagoon, the scientists discovered that dolphins have friends. Instead of spending equal time with the dolphins around them, the animals actually segregate themselves into friend groups. Just like humans, dolphins seem to prefer the company of certain peers more than others.

6. … AND EACH DOLPHIN RESPONDS TO ITS OWN NAME.

Dolphins aren't swimming around with name tags, but every dolphin has its own unique whistle. Scientists believe that dolphins use these signature whistles for life, and female dolphins may even teach their calves their whistles before they're born. Dolphins use their signature whistles to call out to one another and may be able to remember other dolphins' whistles after decades apart.

7. THERE ARE 44 DIFFERENT DOLPHIN SPECIES.

an orca jumping out of the water
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Although bottlenose dolphins are the most well-known and recognizable, there are 43 other dolphin species. Most species live in temperate and tropical oceans, but a few live in colder oceans or rivers. Depending on their species, dolphins can vary considerably in their physical attributes and behavior. For example, the largest dolphin species, the Orca (also called Killer Whale), can be 30 feet long—10 times longer than the smallest dolphins.

8. THEY DON'T USE THEIR TEETH TO CHEW FOOD.

two smiling dolphins
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Dolphins have teeth, but they don't use their chompers to chew food. Instead, dolphins use their teeth to catch prey (fish, crustaceans, and squid) and swallow it whole. Since they forgo chewing, digestion occurs in their stomach—or, more precisely, in part of their stomach. Dolphins have multiple stomach chambers, one of which is devoted to digestion, while the other chambers store food before it's digested.

9. THEY TYPICALLY GIVE BIRTH TO JUST ONE CALF.

mother and baby dolphin
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Depending on their species, most female dolphins (called cows) carry their babies for nine to 17 months before giving birth to a calf. Interestingly, calves are born tail first, rather than head first, so they don't drown during the birthing process. After nursing for one to two years, a calf typically stays with its mother for the next one to seven years, before mating and having its own calves.

10. THEIR SKIN CAN BE REGENERATED EVERY TWO HOURS.

If you've ever swum with dolphins, you know their skin looks and feels super smooth and sleek. There's a reason for that—a dolphin's epidermis (outer layer of skin) can be sloughed off and replaced with new skin cells as often as every two hours. Because their skin regenerates so often, it stays smooth and, as most scientists believe, reduces drag as they swim.

11. THE U.S. NAVY TRAINS DOLPHINS TO PROTECT NUCLEAR WEAPONS.

A bottlenose dolphin named K-Dog from the Commander Task Unit jumps out of the water in 2003. Commander Task Unit is comprised of special mine clearing teams from The United Kingdom, Australia, and the U.S.
A bottlenose dolphin named K-Dog from the Commander Task Unit jumps out of the water in 2003. Commander Task Unit is comprised of special mine clearing teams from The United Kingdom, Australia, and the U.S.
Brien Aho, U.S. Navy/Getty Images

Despite dolphins' general friendliness, some of them are trained for combat. The Navy Marine Mammal Program at San Diego's Space and Naval Warfare Systems Command (SPAWAR) trains dozens of bottlenose dolphins (as well as sea lions) to help the U.S. Navy. In the past, the U.S. military has used dolphins in conflicts in Vietnam and the Persian Gulf. Today, thanks to their intelligence, speed, and echolocation skills, dolphins are trained to find enemy swimmers, locate underwater mines, and guard nuclear arsenals.

12. THEY'RE NOT THE SAME AS PORPOISES.

To the untrained eye, dolphins and porpoises look nearly identical, and many people mistakenly think that porpoises are a type of dolphin. But the two species belong to completely different families and differ in their physical attributes. So how can you tell them apart? Dolphins, which are usually bigger than porpoises, typically have longer beaks and curved dorsal fins. Porpoises, on the other hand, have more triangular dorsal fins as well as spade-shaped (rather than conical) teeth.

13. HUNTING, OVERFISHING, AND RISING OCEAN TEMPERATURES THREATEN THEM.

Some dolphin species are endangered or functionally extinct (like China's baiji dolphin) due to hunting, overfishing, and pollution. Although dolphin meat is high in mercury, the animals are still hunted for their meat and eaten in parts of Japan and the Faroe Islands of Denmark. Overfishing means that dolphins' food sources are shrinking, and some dolphins get caught up in fishing nets and die. Additionally, climate change and rising ocean temperatures are driving some fish and squid away from their natural habitats, putting dolphins' main food source at risk.

14. A SUPERPOD CAN CONSIST OF MORE THAN 1000 DOLPHINS.

a pod of dolphins swimming
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Dolphins live in groups, called pods, that typically contain dozens or hundreds of dolphins. By swimming in a pod, dolphins work together to hunt prey, evade predators, and care for sick or injured members. But different pods can also merge, forming a superpod of more than 1000 dolphins. Superpods are typically temporary and occur in parts of the ocean with plentiful food (and less competition for tasty squid).

15. THE OLDEST DOLPHIN IN CAPTIVITY LIVED TO 61 YEARS OLD.

Dolphin lifespan varies greatly by species. Most dolphins in the wild live for a few decades, while those in captivity have a drastically reduced lifespan and may live for only a few years. So it's all the more shocking that the oldest dolphin in captivity lived to be a sexagenarian. Nellie, a bottlenose dolphin who lived in a marine entertainment park in Florida, was born in 1953. She appeared on TV shows and commercials and performed tricks for the park's attendees before passing away in 2014.

11 Facts About French Bulldogs

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iStock/carolinemaryan

These cute little dogs are enjoying a serious comeback. Here’s the scoop on the fourth most popular dog breed in America. 

1. FRENCH BULLDOGS HAVE ROOTS IN ENGLAND.


iStock/malrok

The French bulldog’s origins are murky, but most sources trace their roots to English bulldogs. Lace makers in England were drawn to the toy version of the dog and would use the smaller pups as lap warmers while they worked. When the lace industry moved to France, they took their dogs with them. There, the English bulldogs probably bred with terriers to create bouledogues français, or French bulldogs. 

2. THEY WERE BRED TO BE GREAT COMPANIONS.

Frenchies are affectionate, friendly dogs that were bred to be companions. Although they’re somewhat slow to be housebroken, they get along well with other dogs and aren’t big barkers. The dogs don’t need much exercise, so they are fine in small areas and enjoy the safety of a crate.

3. THEY CAN'T SWIM.


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As a result of their squat frame and bulbous head, French bulldogs can’t swim, so pool owners should keep a watchful eye on their pups. Keep in mind that if you plan a beach vacation, your furry friend might feel a little left out. 

4. FLYING IS A PROBLEM FOR THEM, TOO.

French Bulldogs are a brachycephalic breed, meaning they have shorter snouts than other dogs. These pushed-in faces can lead to a variety of breathing problems. This facial structure, coupled with high stress and uncomfortably warm temperatures, can lead to fatal situations for dogs with smaller snouts. Many breeds like bulldogs and pugs have perished while flying, so as a result, many airlines have banned them. 

Luckily there are special airlines just for pets, like Pet Jets. These companies will transport dogs with special needs on their own flights separate from their owners. There's a human on board to take care of any pups that get sick or panic. 

5. THEY MAKE GREAT BABYSITTERS.

When a baby orangutan named Malone was abandoned by his mother, the Twycross Zoo in England didn’t know if he would make it. Luckily, a 9-year-old French bulldog named Bugsy stepped in and took care of the little guy. The pair became fast friends and would even fall asleep together. When Malone was big enough, he joined the other orangutans at the zoo. 

6. THEY'RE SENSITIVE TO CRITICISM.

Frenchies are very sensitive, so they do not take criticism lightly. If you scold a French bulldog, it might take it very seriously and mope around the house. French bulldogs respond better to positive reinforcement and encouragement. 

7. THEY'RE A TALKATIVE BREED. 

French bulldogs might not bark much, but they do like to “talk.” Using a complex system of yawns, yips, and gargles, the dogs can convey the illusion of their own language. Sometimes they will even sing along with you in the car. 

8. THEY HAVE TWO STYLES OF EARS. 


iStock/IvonneW

Originally, French bulldogs had rose-shaped ears, similar to their larger relative, the English bulldog. English breeders much preferred the shape, but American breeders liked the unique bat ears. When a rose-eared bulldog was featured at the Westminster Kennel Club in 1897, American dog fanciers were very angry

9. THIS CONTROVERSY LED TO THE FORMATION OF THE FRENCH BULL DOG CLUB OF AMERICA.

The FBDCA was founded in protest of the rose-shaped ears. The organization threw its first specialty show in 1898 at New York City’s famed Waldorf-Astoria. The FBDCA website described the event: “amid palms, potted plants, rich rugs and soft divans. Hundreds of engraved invitations were sent out and the cream of New York society showed up. And, of course, rose-eared dogs were not welcomed.”

The somewhat catty efforts of the club led to the breed moving away from rose-shaped ears entirely. Today, French bulldogs feature the bat-shaped ears American breeders fought to showcase. 

10. MOST FRENCH BULLDOGS ARE BORN THROUGH ARTIFICIAL INSEMINATION. 

Due to their unusual proportions, the dogs have a little trouble copulating. Males have a hard time reaching the females, and they often get overheated and exhausted when trying to get things going. As a result, a large majority of French bulldogs are created through artificial insemination. While this measure makes each litter of pups more expensive, it also allows breeders to check for potential problems during the process. 

French bulldogs often also have problems giving birth, so many must undergo a C-section. The operation ensures the dog will not have to weather too much stress and prevents future health complications.

11. CELEBRITIES LOVE FRENCHIES.

Frenchies make plenty of appearances in the tabloids. Celebrities like Lady Gaga, Hugh Jackman, and The Rock have all been seen frolicking with their French bulldogs. Even Leonardo DiCaprio has one—aptly named Django. Hugh Jackman’s Frenchie is named Dali, after the way the dog’s mouth curls like the famous artist’s mustache. 

This article originally ran in 2015.

What’s That Thing That Hangs Off a Turkey’s Face?

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iStock.com/JZHunt

That thing is called a snood. And it's there to let the other turkeys know that its owner is kind of a big deal.

When a male turkey—known as a tom—wants to mate, he faces two hurdles. One is his potential mates, the female turkeys (a.k.a. hens). In the realm of turkey mating, the hens wield the power of choice and the toms have to get their attention and win the opportunity to reproduce. Come mating season, a tom will strut around, gobble, puff out his chest, fan his tail, and drag his wings to attract the hens, who then pick which of the toms they’ll mate with.

The second problem for a tom looking for love is the other toms in the area. They’re all competing for the same limited number of hens. Sometimes a good mating display isn’t enough to win a mate, and toms will attack and fight each other to secure a hen. 

This is where the snood comes in. That goofy-looking piece of dangling flesh helps a tom both with choosy hens and with competition from rival males. Having a long snood almost always means that a hen will want to mate with him and that another tom will back down from a fight.

DUDES AND THEIR SNOODS

When two toms are trying to establish dominance, they’ll size each other up. Then they'll either fight, or one will flee.

In the late 1990s, Richard Buchholz, an animal behaviorist who focuses on turkeys, wanted to figure out which, if any, characteristics of a tom turkey could predict how they fare in dominance fights. That is, did bigger turkeys tend to win more scuffles? Did older ones? He also wanted to see if the turkeys used any of these predictive cues when sizing each other up. He looked at various characteristics of dominant toms that fight and win, and compared them to those of subordinate toms that lose fights or run from them. Of all the characteristics he looked at, only “relaxed snood length” seemed to be a reliable predictor of how a tom would do in bird-vs-bird combat. The dominant males, the ones who won fights and got a choice mate, had longer snoods.

With that in mind, Buchholz looked at how toms reacted to other toms with snoods of varying sizes. The birds tended to avoid confrontation with other males with longer snoods, and wouldn’t even feed near them. A big snood, this suggests, says to the other turkeys that this is a tom you don’t want to tangle with. Buchholz noted that snood length correlates with age, body mass, and testosterone, so, to competitors, the snood could be a good indicator of a tom’s aggressiveness, age/experience, size, and overall condition and fighting ability.

IN THE SNOOD FOR LOVE

Once the males have established who’s going to have a chance to mate, the final choice goes to the hen. While the mating display is the main draw for getting a hen to check him out, a tom’s snood helps him out again here.

Like it did for the other males, a tom’s snood signals a lot of information to a female assessing potential mates—it indicates how old and how big he is, and even says something about his health. In another study, Buchholz found that longer-snooded toms carried fewer parasites. If a hen wanted to choose a mate with good genes that might help her offspring grow large, live long, and avoid parasites, a tom’s snood is a good advertisement for his genes. In that study, hens showed a clear preference for toms with longer snoods. In another experiment years later, Buchholz found that healthy hens again showed a strong preference for long snoods and that hens with their own parasite problems were less picky about snood length and checked out more potential mates—perhaps, Buchholz thinks, because the hens recognized their own susceptibility to infection and were willing to invest more time searching for a tom with genes for parasite resistance that would complement their own—but still showed some preference for longer ones.

While a snood might look goofy to us, for a turkey, it’s integral to the mating game, signaling to other toms that they should get out of his way and letting hens know that he’s got what they’re looking for.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

An earlier version of this article ran in 2013.

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