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.

14 Adorable, Vintage Photos of Rabbits

Chaloner Woods, Getty Images
Chaloner Woods, Getty Images

In honor of International Rabbit Day (held annually on the fourth Saturday of September), we've pulled photographic proof that the furry little mammals have always been appreciated by children and the adults who use a number of rabbit-related phrases and idioms more often than they probably realize.

1. DOWN THE RABBIT HOLE

Nursery school children playing with their pet rabbit Bubbles; 1939.
David Parker, Fox Photos/Hulton Archive/Getty Images

Nursery school children playing with their pet rabbit Bubbles, 1939.

2. DUST BUNNY

 A woman spinning Angora rabbit wool in her garden, 1930.
Fox Photos, Getty Images

A woman spinning Angora rabbit wool in her garden, 1930.

3. MAD AS A MARCH HARE

A young boy holds a pet rabbit, 1955.
Charles Ley, BIPs/Getty Images

A young boy holds a pet rabbit, 1955.

4. BUY THE RABBIT

A golfer makes a practice drive while his pet rabbit minds the balls; 1938.
Reg Speller, Fox Photos/Hulton Archive/Getty Images

A golfer makes a practice drive while his pet rabbit minds the balls, 1938.

5. HONEY BUNNY

School children petting rabbits; 1949.
Chaloner Woods, Getty Images

Schoolchildren petting rabbits, 1949.

6. HAREBRAINED IDEA

A woman took her Himalayan rabbit, Albrecht Durer, on a walk in Hyde Park, 1939.
Fox Photos, Getty Images

A woman took her Himalayan rabbit, Albrecht Durer, on a walk in Hyde Park, 1939.

7. CUDDLE BUNNY

A little girl petting a large rabbit, 1949.
Chaloner Woods, Getty Images

A little girl petting a large rabbit, 1949.

8. LUCKY RABBIT'S FOOT

Schoolgirls care for pet rabbits, 1932.
Fox Photos, Getty Images

Schoolgirls care for pet rabbits, 1932.

9. PULL A RABBIT OUT OF A HAT

A young magician and his rabbit, 1971.
George W. Hales, Fox Photos/Getty Images

A young magician and his rabbit, 1971.

10. SNOW BUNNY

A woman shows off her two pet angora rabbits, circa 1955.
George Pickow, Three Lions/Getty Images

A woman shows off her two pet angora rabbits, circa 1955. Angoras can be sheared to provide enough wool for two sweaters each year.

11. THE EASTER BUNNY

A little girl holds an Easter bunny on a leash, circa 1955.
George Pickow, Three Lions/Getty Images

A little girl holds an Easter bunny on a leash, circa 1955.

12. A RABBIT TRAIL

Three children hold a rabbit, 1935.
H. Allen, Topical Press Agency/Getty Images)

Three children hold a rabbit, 1935.

13. RABBIT FOOD

A boy feeds his pet rabbit a lettuce leaf, circa 1955.
George Pickow, Three Lions/Getty Images

A boy feeds his pet rabbit a lettuce leaf, circa 1955.

14. RABBITING ON

Actresses Fiona Fullerton and Clare Clifford posting some of the many letters sent to the House of Lords and parliamentary candidates to request support for World Day for Laboratory Animals which was instituted that year, 1979.
Central Press, Getty Images

Actresses Fiona Fullerton and Clare Clifford posting some of the many letters sent to the House of Lords and parliamentary candidates to request support for World Day for Laboratory Animals which was instituted that year, 1979.

How a Wildlife Center Untangled Five Squirrels' Tails

Wisconsin Humane Society
Wisconsin Humane Society

Five juvenile gray squirrels in Wisconsin found themselves in a hairy situation recently. As The Guardian reports, bits of plastic and grass from their mother's nest got caught in their tails. Then the five tails became entangled, forming one solid knot.

This could have been a fatal situation had it not been for a "caring finder" who happened upon the squirrels and brought them to the Wildlife Rehabilitation Centre at the Wisconsin Humane Society in Milwaukee.

"You can imagine how wiggly and unruly (and nippy!) this frightened, distressed ball of squirrelly energy was, so our first step was to anesthetize all five of them at the same time," the rehabilitation center wrote in a Facebook post on September 14. "With that accomplished, we began working on unraveling the 'Gordian Knot' (Google it) of tightly tangled tails and nest material." (For the record, a Gordian knot refers to a difficult problem and stems from a legend involving Alexander the Great.)

Next, they used scissors to carefully cut away the plastic and grass while taking care not to snip their tails, which had already sustained tissue damage due to the blood supply being cut off. After about 20 minutes, they were finally freed. Now, the squirrels have fully recovered and are "very active and vigorous." Staff at the center are still watching for signs of tail necrosis—the death of cells and tissue—but otherwise, the fur babies are expected to make a full recovery.

Tangled tails are not uncommon in the animal kingdom. A group of rats with entangled tails is called a "rat king," and the phenomenon has been reported since at least the mid-16th century. There's no equivalent term for when this happens to squirrels, although it does occur from time to time.

[h/t The Guardian]

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