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11 Facts About Tiger Sharks

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Weighing 1300 pounds or more and growing up to 15 feet, the tiger shark is the fourth-largest shark on earth. (Only whale sharks, basking sharks, and great whites get bigger.) On top of being big, tiger sharks are also pretty bizarre: They literally eat garbage, give birth to massive litters—and one of them was a player in Australia’s greatest unsolved murder mystery.

1. THEY’RE LIKE SWIMMING GARBAGE DISPOSALS.

Tiger sharks have broad diets: They eat everything from albatrosses, venomous sea snakes, and other sharks to manmade objects like paint cans, leather jackets, rubber tires, and even license plates. (That scene in Jaws where Hooper pulls a Louisiana plate from the stomach of a dead tiger shark is scientifically accurate!)

2. DON’T CONFUSE THEM WITH SAND TIGER SHARKS.

You might assume that the tiger shark (Galeocerdo cuvier) and the sand tiger shark (Carcharias taurus) are cousins, but the latter is more closely related to the great white (Carcharodon carcharias) than it is to the tiger shark.

3. NOT ALL OF THEM HAVE STRIPES.

Hear the word tiger and you think vertical stripes, but those stripes evolve over time. Baby tiger sharks—a.k.a. pups—are covered in roundish gray spots that fuse into stripes as the sharks mature. After a certain age, the stripes start to fade; they’re barely visible in full-grown adults.

4. TIGER SHARKS PREFER WARM WATER.

Tiger sharks are seen in tropical to warm temperate waters all over the world, and a study published in Global Change Biology in March 2018 revealed that the sharks have a "Goldilocks" zone. “Our study suggests that 22 degrees [Celsius, 71.6 degrees Fahrenheit] is not too cold for the animals and it’s not too hot for them,” lead author Nicholas Payne told the BBC. “It’s about right in terms of their optimal preference for temperature.” The scientists reached that conclusion after monitoring tagged sharks near Hawaii and comparing those findings to several decades’ worth of Australian fishing records.

5. THEY HAVE NOTCHED TEETH.

the teeth of the tiger shark with serrated edges

If you could pry open a tiger shark’s jaws, you’d see teeth with dramatic notch tips that point sideways. You'd also notice that the teeth on the left and right halves look like mirror images of each other. A tiger shark’s teeth have a dual function: They help the fish grasp onto struggling victims and can shear right through the thickest of hides, making them well-equipped to go after just about any prey that’s available.

6. THEY MIGHT BE THE ONLY SHARKS TO REGULARLY HUNT SEA TURTLES.

Every year, 12,000 nesting sea turtles visit Raine Island in the Great Barrier Reef, and tiger sharks—which hunt the turtles—aren't far behind.

To get its meal, the shark first has to get a good grip, but the turtle doesn't make it easy: When a shark gets too close for comfort, a turtle may respond by turning itself sideways so the top of the carapace is perpendicular to the shark’s jaws, making themselves too wide to bite into. Turtles in this position will also swim in tight circles around the predator, which protects the reptile’s vulnerable flanks.

According to a 2016 study, the sharks tend to avoid healthy turtles and instead conserve energy by going after sick or dying (or dead) turtles.

7. SEA GRASS SEEMS TO BENEFIT WHEN TIGER SHARKS ARE AROUND.

Though Australia's Shark Bay is home to a diverse array of organisms, it got its moniker for the 28 shark species that have been seen there—including tigers, which are especially common.

Sea grasses are the backbone of Shark Bay's ecosystem; they provide shelter for small animals and food for big herbivores. But the grasses were decimated after a 2011 heat wave. Since then, they've been making a gradual comeback, and scientists have noticed that they grow at a higher rate in places frequented by tiger sharks. This is probably because the sharks frighten off sea turtles and dugongs who like to eat the grass. “Just the fear of sharks can be enough, in many cases, to keep a marine ecosystem healthy and able to respond to stresses,” biologist Michael Heithaus said in a news release.

8. TIGER SHARKS GIVE BIRTH TO HUGE LITTERS.

Female tiger sharks are pregnant for 14 to 16 months and give birth to at least 10 pups, with around 30 being the average. But sometimes, they have many, many more than that: There have been reports of females birthing 80 pups at once. Usually, newborns weigh between six and 13 pounds.

9. IN THE ATLANTIC, THEY MIGRATE SOUTH FOR THE WINTER.

There's still a lot to learn about the travel habits of tiger sharks. A seven-year study found that Hawaiian females tend to travel more often—and more widely—around the island chain than males do. Another analysis, published in 2015 in Scientific Reports, focused on 24 adult tiger sharks in the Atlantic and found that, in the winter months, they stayed in the area around the Caribbean and West Indies. Then, for summer, they headed north and spent the warmest part of the year in the mid-Atlantic, venturing as far north as Connecticut (and far away from the coast). No one knows why the sharks make the trip, but it may have something to do with the young loggerhead turtles who dwell in those northern waters.

10. ONE TIGER SHARK BARFED UP A MURDER MYSTERY.

In April 1935, Coogee Aquarium in Sydney, Australia was looking for a big fish to occupy its newly-built pool. On a fishing trip off Coogee beach, Bert Hobson snared a 13-foot tiger shark for the aquarium.

The shark was a big hit at the aquarium, but it didn’t last very long. Seven days after its arrival, it got sick and vomited up a bird, a rat, some nasty-looking brown goo—and a human arm, which had a rope tied around its wrist and a forearm tattoo of two boxers.

An amateur boxer named James Smith had recently gone missing, and he had the exact same tattoo on one arm. Forensic analysis determined that the arm hadn’t been bitten off—it had been removed from the rest of Smith's body with a knife.

Detectives learned that Smith was last seen playing cards at the Hotel Cecil in Cronulla with his longtime associate Patrick Brady, a forger, who quickly became the number one suspect. The authorities were later informed by a boat-builder (and suspected criminal) named Reginald Holmes that Brady had murdered Smith in an argument. But before Holmes could testify in court, somebody shot him.

Brady's lawyers argued that a severed arm didn’t constitute proof of a murder. Smith, they argued, might still be alive somewhere—sans one limb, of course. Brady got off scot-free, which was more than could be said for the poor tiger shark—it died in captivity. A necropsy did not reveal any other human remains.

11. IT’S RARE, BUT TIGER SHARKS HAVE BEEN KNOWN TO SHARE FOOD WITH CROCODILES AND GREAT WHITES.

Bloated, rotting whale carcasses lure all kinds of animals out of the woodwork. Carnivores that normally don’t cross paths sometimes end up feasting on the dead mammals side-by-side. In 2015, two great whites and three tiger sharks were filmed tearing into the colossal body of a sperm whale near New South Wales, Australia. Years earlier, off the South African coastline, witnesses saw members of both species eating a Byrd’s whale carcass [PDF]. Australian drone footage from 2017 (above) shows a humpback carcass getting picked apart by both tiger sharks and saltwater crocodiles. Look at the video closely and you’ll see the croc and fish coming within a few yards of each other.

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14 Bold Facts About Bald Eagles
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Bald eagles are powerful symbols of America—but there’s a whole lot more to these quirky birds.

1. YOUNG BALD EAGLES AREN'T BALD.

A young bald eagle with a brown head on a beach.
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So obviously adult bald eagles aren't really bald, either—their heads have bright white plumage that contrasts with their dark body feathers, giving them a "bald" look. But young bald eagles have mostly brown heads. In fact, for the first four or five years of their lives, they move through a complicated series of different plumage patterns; in their second year, for instance, they have white bellies.

2. BALD EAGLES SOUND SO SILLY THAT HOLLYWOOD DUBS OVER THEIR VOICES.

A red-tailed hawk.
A red-tailed hawk's screech is usually dubbed over the bald eagle's weaker scream.
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It's a scene you’ve probably seen countless times in movies and on TV: An eagle flies overhead and emits a rough, piercing scream. It's a classic symbol of wilderness and adventure. The only problem? Bald eagles don't make that sound.

Instead, they emit a sort of high-pitched giggle or a weak scream. These noises are so unimpressive that Hollywood sound editors often dub over bald eagle calls with far more impressive sounds: the piercing, earthy screams of a smaller bird, the red-tailed hawk. If you were a fan of The Colbert Report, you might remember the show's iconic CGI eagle from the opener—it, too, is making that red-tailed hawk cry. Listen for yourself and decide who sounds more impressive.

3. THEY EAT TRASH AND STOLEN FOOD.

Two bald eagles guard their prey against two magpies on a snowy field.
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Picture a majestic bald eagle swooping low over a lake and catching a fish in its powerful claws. Yes, bald eagles eat a lot of fish—but they don't always catch them themselves. They've perfected the art of stealing fish from other birds such as ospreys, chasing them down until they drop their prey.

Bald eagles will also snack on gulls, ducks, rabbits, crabs, amphibians, and more. They'll scavenge in dumpsters, feed on waste from fish processing plants, and even gorge on carrion (dead, decaying animals).

4. BALD EAGLES USUALLY MATE FOR LIFE ...

Two bald eagles perched on a tree.
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Trash and carrion aside, they're pretty romantic animals. Bald eagles tend to pair up for life, and they share parenting duties: The male and the female take turns incubating the eggs, and they both feed their young.

5. … AND THEY LIVE PRETTY LONG LIVES.

Two bald eagles sitting on a rock.
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Those romantic partnerships are even more impressive because bald eagles can survive for decades. In 2015, a wild eagle in Henrietta, New York, died at the record age of 38. Considering that these birds pair up at 4 or 5 years of age, that's a lot of Valentine's Days.

6. THEY HOLD THE RECORD FOR THE LARGEST BIRD'S NEST.

Two bald eagles in their large nest.
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Bald eagles build enormous nests high in the treetops. The male and female work on the nest together, and this quality time helps them cement their lifelong bond. Their cozy nurseries consist of a framework of sticks lined with softer stuff such as grass and feathers. If the nest serves them well during the breeding season, they'll keep using it year after year. And, like all homeowners, they can't resist the thought of renovating and adding to their abode. Every year, they'll spruce it up with a whopping foot or two of new material.

On average, bald eagle nests are 2-4 feet deep and 4-5 feet wide. But one pair of eagles near St. Petersburg, Florida, earned the Guinness World Record for largest bird’s nest: 20 feet deep and 9.5 feet wide. The nest weighed over two tons.

7. FEMALES ARE LARGER THAN MALES.

Two bald eagles in their large nest.
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In many animal species, males are (on average) larger than females. Male gorillas, for example, dwarf their female counterparts. But for most birds of prey, it's the opposite. Male bald eagles weigh about 25 percent less than females.

Scientists aren't sure why there's such a size difference. One reason might be the way they divide up their nesting duties. Females take the lead in arranging the nesting material, so being bigger might help them take charge. Also, they spend longer incubating the eggs than males, so their size could intimidate would-be egg thieves.

If you're trying to tell male and female eagles apart, this size difference may help you—especially since both sexes have the same plumage patterns.

8. TO IDENTIFY THEM, LOOK AT THE WINGS.

A bald eagle flies across the water.
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People often get excited about a big soaring bird and yell "It's an eagle!” just before it swoops closer and … oops, it's a vulture. Here's a handy identification tip. Bald eagles usually soar with their wings almost flat. On the other hand, the turkey vulture—another dark, soaring bird—holds its wings up in a shallow V shape called a dihedral. A lot of large hawks also soar with slightly raised wings.

9. THEY'RE COMEBACK KIDS.

Baby eagle chicks in a nest.
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Before European settlers arrived, bald eagles were abundant across the U.S. But with settlement came habitat destruction, and the settlers viewed the eagles as competition for game and as a threat to livestock. So many eagles were killed that in 1940 Congress passed an act to protect the birds.

Unfortunately, another threat rose up at about that time. Starting after World War II, farmers and public health officials used an insecticide called DDT. The chemical worked well to eradicate mosquitos and agricultural pests—but as it traveled up the food chain, it began to heavily affect birds of prey. DDT made eagle eggshells too thin and caused the eggs to break. A 1963 survey found just 471 bald eagle pairs in the lower 48 states.

DDT was banned in the early 1970s, and conservationists began to breed bald eagles in captivity and reintroduce them in places across America. Luckily, this species made a spectacular recovery. Now the lower 48 states boast over 9700 nesting pairs.

10. THEY'RE UNIQUELY NORTH AMERICAN.

An African fish eagle flies over the water.
The African fish eagle is a relative of the North American bald eagle.
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You've probably heard of America's other eagle: the golden eagle. This bird lives throughout much of the northern hemisphere. But the bald eagle is only found in North America. It lives across much of Canada and the U.S., as well as northern parts of Mexico.

Though it may be North American, the bald eagle has seven close relatives that are found throughout the world. They all belong to the genus Haliaeetus, which comes—pretty unimaginatively—from the Latin words for "sea" and "eagle." One relative, the African fish eagle, is a powerful symbol in its own right. It represents several countries; for example, it's the national symbol of Zambia, and graces the South Sudanese, Malawian, and Namibian coats of arms.

11. THEY'RE AERIAL DAREDEVILS.

A bald eagle carries a fish off in its talons.
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It seems too weird to be true: While flying, bald eagles sometimes grab each other's feet and spin while plummeting to the earth. Scientists aren't sure why they do this—perhaps it's a courtship ritual or a territorial battle. Usually, the pair will separate before hitting the ground (as seen in this remarkable set of photographs). But sometimes they hold tight and don't let go. These two male bald eagles locked talons and hit the ground with their feet still connected. One subsequently escaped and the other was treated for talon wounds.

12. THEIR EYES ARE AMAZING.

Close-up of a bald eagle's face.
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What if you could close your eyes and still see? Besides the usual pair of eyelids, bald eagles have a see-through eyelid called a nictitating membrane. They can close this membrane to protect their eyes while their main eyelids remain open. The membrane also helps moisten and clean their eyes.

Eagles also have sharper vision than people, and their field of vision is wider. Plus, they can see ultraviolet light. Both of those things mean the expression "eagle eye" is spot-on.

13. THEY MIGRATE … SORT OF.

A bald eagle sits in a snowy tree.
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If you're a bald eagle that nests in northern Canada, you'll probably head south for the winter to avoid the punishing cold. Many eagles fly south for the winter and return north for the summer—as do plenty of other bird species (and retired Canadians). But not all bald eagles migrate. Some of them, including individuals in New England and Canada's Maritime provinces, stick around all year. Whether or not a bird migrates depends on how old it is and how much food is available.

14. THEY CAN SWIM … SORT OF.

A bald eagle
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There are several videos online—like the one above—that show a bald eagle swimming in the sea, rowing itself to shore with its huge wings. Eagles have hollow bones and fluffy down, so they can float pretty well. But why swim instead of soar? Sometimes, an eagle will swoop down and grab an especially weighty fish, then paddle it to shore to eat.

Note that the announcer in the video above says that the eagle's talons are "locked" on a fish that's too heavy to carry. In fact, those lockable talons are an urban legend.

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How Bats Protect Rare Books at This Portuguese Library
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Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

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