16 Fun Facts About Hedgehogs

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After cats, hedgehogs might be the internet's favorite animal. But how much do you know about these spiky mammals—other than how cute they look when getting a bath?

1. A GROUP OF HEDGEHOGS IS CALLED AN "ARRAY."

Hedgehogs poking around in the dirt.
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But it doesn't come up much, since hedgehogs are solitary creatures who usually come together only to mate.

2. HEDGEHOGS ARE ILLEGAL IN SOME PARTS OF THE UNITED STATES.

Hedgehog in a bucket with purple beads.
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The hedgie has gained some popularity as a pet—but some cities and states still qualify them as wild animals, which are not allowed to be kept domestically. These include Arizona, California, Georgia, Hawaii, Pennsylvania, and New York City and Washington, D.C. In some areas, like Maine, you need permits in order to own one.

3. A HEDGEHOG HAS BETWEEN 5000 AND 7000 QUILLS.

Hedgehog in a garden.
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Muscles along the animal's back can raise and lower the quills to respond to threatening situations.

4. THERE ARE 17 DIFFERENT SPECIES OF HEDGEHOG, NONE OF WHICH ARE NATIVE TO AMERICA.

Two African hedgehogs.
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Australia also has no indigenous hedgehogs; the hedgies in New Zealand were introduced by humans.

5. HEDGEHOGS RELY ON HEARING AND SMELL BECAUSE THEY HAVE VERY POOR EYESIGHT.

Hedgehog looking for strawberries.
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And even their limited sight is best in the dark as an adaption to their nocturnal lifestyle.

6. UNLIKE PORCUPINE QUILLS, HEDGEHOG SPIKES ARE NOT BARBED, AND THEY'RE NOT POISONOUS.

A close-up of hedgehog quills.
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The inside of the quills are mostly hollow, with a series of complex air chambers that make them light but strong.

7. HEDGEHOGS GOT THEIR NAME FROM THEIR PREFERRED HABITAT—GARDEN HEDGES—AND THE PIG-LIKE GRUNTS THEY MAKE.

Hedgehog playing in purple flowers.
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Their taste for destructive insects makes them a historically welcome presence in English gardens.

8. HEDGEHOGS CAN HIBERNATE, BUT NOT ALL DO.

A hedgehog rolled up in a little ball on some leaves.
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Which makes them one of only three mammals in Great Britain that hibernate (the other two being bats and dormice).

9. HEDGEHOGS ARE LARGELY IMMUNE TO SNAKE VENOM.

Baby hedgehogs nursing on their mother.
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This means that, although their typical diet consists of insects and berries, they can take down a viper in a fight and eat it, too.

10. THE SEA URCHIN IS ACTUALLY NAMED AFTER THE HEDGEHOG.

A baby hedgehog lying in a human hand.
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Before the more adorable name came into use, the spiky mammals were called "urchins" throughout the Middle Ages, and thus inspired the name of the similarly spiky sea creatures. Baby hedgehogs are still called urchins.

11. MEDIEVAL BESTIARIES AND ILLUMINATED TEXTS SHOW HEDGEHOGS GATHERING FOOD WITH THEIR QUILLS.

Hedgehog with two cherries stuck on his quills.
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This is inaccurate. But affinity for the image has persisted.

12. IN THE PRECURSOR TO GROUNDHOG DAY, HEDGEHOGS WERE THE SUPPOSEDLY PORTENTOUS CRITTERS.

Hedgehog curled up on some pine branches.
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But when German settlers got to America and found no hedgehogs, they turned to the similar-enough groundhog for their winter-weather predictions.

13. IN NEW ZEALAND, A SATIRICAL POLITICAL PARTY TRIED TO GET A HEDGEHOG ELECTED TO PARLIAMENT.

Little hedgehog walking in fall leaves.
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The McGillicuddy Serious Party was unsuccessful with their tiny candidate.

14. THERE USED TO BE SUCH A THING AS THE INTERNATIONAL HEDGEHOG OLYMPIC GAMES (IHOG).

Hedgehog swimming in a pool.
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Events included sprints, hurdles, and floor exercises.

15. ONE OF THE LESSER-KNOWN BROTHERS GRIMM FAIRY TALES IS CALLED HANS-MY-HEDGEHOG, ABOUT A BOY WHO IS BORN HALF HEDGEHOG.

Two hedgehogs cuddled in the grass.
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Not your style? Try another Grimm tale, The Hare and The Hedgehog.

16. WHEN EXPOSED TO PUNGENT SMELLS OR TASTES, HEDGEHOGS EXHIBIT A BEHAVIOR CALLED "SELF-ANOINTING," IN WHICH THEY RUB FROTHY SALIVA ON THEIR QUILLS.

Hedgehog sleeping with a leg out.
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The purpose of this behavior is unknown.

A version of this list first ran in 2016.

New Study Reveals 'Hyper-Alarming' Decline of Rainforest Insect Populations

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iStock/jmmf

Climate change is decimating yet another vital part of the world's ecosystem, according to a startling new paper. Rainforest insects are dying off at alarming rates, according to a new study spotted by the The Washington Post. In turn, the animals that feed off those insects are decreasing, too.

In the study, published in Proceedings of the National Academy of Sciences, a pair of scientists from the Rensselaer Polytechnic University in New York and the National Autonomous University of Mexico studied populations of rainforest arthropods (an invertebrate classification that includes insects and spiders) in the El Yunque National Forest in Puerto Rico. They compared the number of insects lead author Bradford Lister found on trips in 1976 and 1977 with the number he and co-author Andres Garcia found on trips they took between 2011 and 2013.

Lister and Garcia used nets and sticky traps to collect insects on the ground and several feet above the ground in the forest canopy. They dried these captured bugs and measured the mass of their haul against the mass of insects found in the 1970s, finding that the modern net sweeps captured only an eighth to a fourth of the insects captured in the '70s. The mass of insects captured by sticky traps on the ground declined by 30 to 60 times what they were a few decades ago. They also tracked populations of lizards, frogs, and birds that live off those rainforest insects, finding that those populations had declined significantly, too, at levels not seen in other rainforest animals that don't rely on insects for food.

Tropical insects are particularly vulnerable to climatic changes, since they can't regulate their body temperature. During the time of the study, average maximum temperatures in El Yunque rose by almost 4°F (2°C). The warming climate is "the major driver" of this decline in arthropod populations, the study authors write, triggering a collapse of the forest food chain.

The paper has other scientists worried. "This is one of the most disturbing articles I have ever read," University of Connecticut entomologist David Wagner, who wasn't involved in the research, told The Washington Post, calling the results "hyper-alarming." Other studies of insect populations have found similarly dire results, including significant declines in butterflies, moths, bees, and other species. One recent study found that Germany's flying insect populations had decreased by as much as 75 percent in the last three decades. Scientists don't always attribute those population losses directly to warmer temperatures (habitat loss, pesticide use, droughts, and other factors might play a role), but it’s clear that insect populations are facing grave threats from the modern world.

Not all insect species will be equally affected by climate change, though. While we may see a sharp drop in the populations of tropical insects, scientists project that the number of insects in other regions will rise—leading to a sharp increase in crop-eating pests in some parts of the world and broadening mosquitos' geographical range.

[h/t The Washington Post]

13 Chill Facts About Sloths

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iStock.com/janossygergely

Sloths seem to be everyone's "spirit animal." They get to eat, sleep, and hang out in trees all day, going about their business without a care in the world. Or at least that's how it looks. As it turns out, there are plenty of good reasons why sloths are so sluggish—and laziness isn't one of them. Here are 13 things you should know about the world's slowest animal.

1. TWO-TOED AND THREE-TOED SLOTHS AREN'T ALL THAT SIMILAR.

A baby two-toed sloth
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The cute little babe pictured above is a two-toed sloth, of which there are two species belonging to the Megalonychidae family. The four species of three-toed sloths, on the other hand, are part of the Bradypodidae family. The two groups are only distant relatives and have a few notable differences between them. While three-toed sloths are active in the daytime, two-toed sloths are nocturnal creatures. Three-toed sloths are also smaller and slower than their two-toed counterparts.

2. BOTH HAVE THREE TOES, THOUGH.

A two-toed sloth
Tim Evanson, Flickr // CC BY-SA 2.0

The names used to distinguish the sloths are somewhat of a misnomer. Both have three toes on each hind limb. The real difference applies to the fingers on their forelimbs; one family has two claws, while the other has three. To avoid confusion, some groups—like The Sloth Conservation Foundation—have starting calling them two-fingered and three-fingered sloths.

3. THEY'RE RELATED TO THE EXTINCT GIANT GROUND SLOTH.

Illustration of a giant sloth
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Two-toed and three-toed sloths both evolved from giant ground sloths, the largest of which weighed several tons and stood about 12 feet tall. The animals went extinct about 10,000 years ago, likely due to hunting by early humans.

4. THEY WOULD FAIL AN EYE EXAM.

Close-up of a sloth
iStock.com/BrianLasenby

Sloths aren't exactly known for their sharp senses, and this is especially true for their eyesight. A mama three-toed sloth can't spot her own baby from 5 feet away, and combative male sloths have been observed trying to hit each other from a similar distance. Scientists say a genetic mutation is to blame. Three-toed sloths are born without cone cells in their eyes, which are needed to detect colors. As a result, they see things in black and white, and in poorer resolution, too. They also have a hard time handling bright lights—not the best trait for a diurnal (daytime) creature to have.

5. THEY'RE SURPRISINGLY GOOD SWIMMERS.

Sloths are painfully sluggish on land. Their hind legs are weak, so they have to use their arms and upper body strength to pull themselves forward. Plop them in some water, though, and they can move three times as fast. Their long front arms make them skillful swimmers, and they can hold their breath underwater for up to 40 minutes. If a body of water is nearby, they may jump in and use it as a shortcut to navigate the forest more quickly. In the above clip narrated by David Attenborough, a male sloth swims as fast as he can—which is pretty fast, all things considered—to track down a female sloth's mating call.

6. THEIR "LAZINESS" IS A SURVIVAL TACTIC.

A sloth in a chair
iStock.com/GeorgePeters

It's no secret that sloths are slow. Their reaction time is about a quarter as fast as a human's, and they move at a pace of 6 to 8 feet per minute. Indeed, three-toed sloths are the slowest animals on Earth, beating out other famously slow animals like giant tortoises and snails. When the animals were first documented in 18th-century scientific texts, they were harshly described as "the lowest form of existence." But their slowness is why they haven't died out. Sloths largely subsist on leaves, and it can take up to a month for their four-part stomachs to digest a single meal. The leafy greens aren't very nutritious, so they have to conserve as much energy as possible to survive—and that means moving less. As a bonus, their slow movements help them go unnoticed by predators that rely on sight to hunt down prey, like jaguars, ocelots, and harpy eagles.

7. THEY DO JUST ABOUT EVERYTHING IN TREES …

A baby sloth hangs from a branch
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Sloths are arboreal creatures, so they spend almost all of their time in trees. They eat, sleep, mate, and give birth while hanging upside-down—a feat made possible by their anatomy. Their internal organs are anchored to their abdomen, which shifts weight away from their diaphragm and lets them breathe more easily, and therefore expend less energy.

Three-inch claws also help them latch onto branches and stay suspended far above the forest floor. In fact, their innate ability to cling to branches is so strong that dead sloths have been found dangling from trees, lending new meaning to the phrase "death grip."

8. … EXCEPT POOP.

A sloth on the ground
iStock.com/Damocean

As a consequence of their slow metabolisms, sloths poop once a week—and sometimes just once a month. Two-toed sloths often let 'er rip from the trees, but three-toed sloths follow a bizarre routine that has baffled scientists. They typically make their way down to the forest floor to relieve their backed-up bowels, and once they get there, they do a little "poo dance" while digging a small hole to defecate inside. Without the camouflage afforded to them by the foliage of the forest canopy, sloths are much more likely to be picked off by predators. About half of all sloth fatalities occur when they're on the ground, most likely doing their business or finishing up. So why do they do it? It might have something to do with sex, and marking a tree for a potential mate to find. "Whatever is going on, it's got to be kind of life or death for survival," sloth biologist Rebecca Cliffe tells The Washington Post. "In my brain, that tells me that it's probably something to do with reproduction because that is the driving fact behind most animals' crazy behaviors."

9. AND THEIR POOPS ARE ENORMOUS.

A man holds a sloth
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When they do poop, their turds tend to be massive. If you put the contents of a sloth's bowel movement on a scale, they might weigh up to one-third of the animal's body weight. This is 282 percent larger than what scientists would expect to see in an animal of the sloth's size. "You can watch their stomachs physically shrink as they poo," Cliffe tells The Washington Post. Oddly enough, though, sloths don't fart. So there's that.

10. ALGAE OFTEN GROWS ON THEIR FUR.

A sloth covered in algae
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Sloths have a symbiotic relationship with algae. Studies have shown that algae is sometimes passed down from a mother sloth to her baby, and the transfer is mutually beneficial for both animal and plant. The sloth's long fur creates a cozy home for the algae—which readily absorbs the water they need to thrive—and the sloths get a coat of green-tinted fur that doubles as camouflage. Sloths also eat the algae, which provides a much-needed source of nutrients.

11. FEMALE SLOTHS SCREAM WHEN THEY WANT TO MATE.

Females get the courting process started by letting out a loud, high-pitched scream to let male sloths know she's ready to mate. "This call is a loud 'eeeeeh' lasting more or less one second," sloth researcher Adriano Chiarello tells Live Science. Researchers are unsure on the particulars of sloth courting or copulation, or even if males will fight for the right mate with the screeching female (or if any fights are territorial instead). Whatever the details, the ensuing gestation period is between five and six months, and then the female sloth will birth one baby sloth, which is—uninterestingly—just called a baby sloth.

12. THREE-TOED SLOTHS CAN ROTATE THEIR HEADS 270 DEGREES.

A sloth turns its head to look back
iStock.com/MikeLane45

This special talent puts three-toed sloths in the same category as many owls. In both species, this Exorcist-esque ability can be attributed to their bone structure. Sloths have extra vertebrae at the base of their necks that let them look in all directions with ease. Although sloths aren't great at defending themselves, they can at least see when danger is approaching.

13. FOR SUCH DEFENSELESS CREATURES, THEY LIVE FAIRLY LONG LIVES.

A sloth peeks out from behind a tree
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"Live slow, die whenever"—the unofficial slogan bestowed upon sloths by the internet—pretty much gets it right. On average, sloths live to be about 20 years old, but some species can live longer in captivity. The world's oldest sloth—a female of the Hoffman's two-toed variety named Miss C—died last year at the ripe old age of 43. She was a lifetime resident of Australia's Adelaide Zoo.

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