11 Facts About the Sand Tiger Shark

iStock
iStock

If you’ve ever been to a major aquarium, there’s a good chance you've been face to fin with a sand tiger shark. Here’s everything you should know about this wicked-looking—but pretty mild-mannered —creature.

1. IT BELONGS TO THE SAME ORDER OF SHARKS AS THE GREAT WHITE.

The sand tiger shark (Carcharias taurus) isn't related to the tiger shark (Galeocerdo cuvier), but it does have something in common with another popular species—the great white (Carcharodon carcharias). They're both Lamniformes, an order of sharks that share a signature look: five pairs of gill slits, two dorsal fins without spines, a relatively big mouth, and a lack of nictitating membranes, the protective, see-through shields over the eyes that many other sharks possess. Other Lamniformes are the basking shark, the goblin shark, and the prehistoric megalodon shark. True tiger sharks don’t make the cut; they’re part of a different order known as the Carcharhiniformes.

2. THOSE SCARY TEETH ARE LIKE DENTAL FISHING HOOKS.

Look at a sand tiger and the first thing you’ll notice will probably be its long, outward-pointing teeth, which remain visible even when the shark’s mouth is closed. Curved, slender, and serration-free, the teeth are perfect for puncturing the skins of small to mid-sized fish: slippery animals that can be hard to grab onto. This is in marked contrast to both the can-opener-shaped teeth we see in “real” tiger sharks and the thick slicing teeth of big-game hunters like great whites.

3. SAND TIGERS GULP AIR TO STAY BUOYANT.

By swallowing mouthfuls of air at the ocean’s surface, sand tigers can turn their stomachs into air pockets. Doing so helps the fish keep a neutral buoyancy level under the surface, enabling them to hover around motionlessly. (When it descends, the animal releases air bubbles out of its mouth.) No other shark exhibits this air-gulping behavior.

4. VIOLENT ENCOUNTERS WITH HUMANS ARE RARE.

Sand tigers tend to shy away from people, but they have been known to steal fish from spear- and net-hunters. That can bring them into conflict with humans, and when the sharks feel threatened, they may bite back in self-defense.

Still, according to the International Shark Attack File (ISAF), a global database maintained by the Florida Museum of Natural History, sand tigers have only been implicated in 29 “unprovoked attacks” on human beings since 1580. None of those attacks were fatal.

5. OVERFISHING HAS HURT THE SPECIES.

Sand tigers might not pose much of a threat to us, but through sport and commercial fishing, we’ve done a number on them.

Full-grown sand tigers are around 10 feet long and can weigh over 400 pounds. For decades, their intimidating size made the sharks prized trophies amongst recreational fishermen. From June to September 1918, 1900 sharks—primarily sand tigers—were caught in the area of Nantucket Sound. They continue to be hunted in some corners of the world for their meat, skin, teeth, and fins.

Because sand tigers tend to mate near shorelines, it's easy to net large numbers of them during the breeding season. Scientists estimate that the population living along the U.S. eastern seaboard shrank by 70 to 90 percent in the late 20th century due to overzealous commercial fishermen. A slow reproductive rate further handicaps the species, as does coastal pollution in the estuaries where their young tend to reside.

The International Union for Conservation of Nature (IUCN) lists the sand tiger shark as “vulnerable”—the ranking given to creatures that are at risk of becoming endangered. Sand tigers now enjoy protected status in Australia and the United States.

6. IT’S CALLED THE “GREY NURSE SHARK” IN AUSTRALIA.

This is another name which doesn’t make evolutionary sense because the species isn’t related to actual nurse sharks. Sand tigers have also been referred to as “spotted ragged tooth sharks” because adults and juveniles occasionally come with reddish-brown spots on their backsides.

7. EMBRYOS CANNIBALIZE EACH OTHER.

Male sharks have two fin extensions, called claspers, that they use to deliver sperm into a female sand tiger shark's two uteri, both of which are capable of hosting five to seven developing embryos.

Not all of them will be born, though—in fact, the majority won’t. About five months into a nearly year-long gestation, a few of the eggs will begin to hatch and swim around the uterus. And they're hungry. To survive, the biggest fetuses devour unhatched eggs and smaller, weaker siblings who have already hatched out. When the mother finally gives birth, only two shark pups will remain—one for each uterus.

By shark standards, newborn sand tigers are exceptionally large, stretching up to 3 feet long apiece. At that size, the juvenile sharks have an easy time fighting off many would-be predators after they're born. Bulking up on their siblings beforehand might be a secret of survival.

The practice might also be a matter of sexual selection: Female sand tigers tend to mate with several different partners each breeding season, and it's been hypothesized that the eggs from the first encounter will be the earliest to fertilize. As a consequence, they’ll grow faster and be more likely to gobble up all the rival fetuses sired by other males. So in theory, a female sand tiger could choose to mate with her preferred partner first, giving his unborn offspring the best chance of survival.

8. LONG ISLAND HAS A SAND TIGER NURSERY.

To get away from adults who might attack them, pups (a.k.a. juvenile sharks) often spend a few months out of every year in shark nurseries: shallow, relatively secluded parts of the ocean where full-grown sharks are less common than they might be elsewhere. In 2016, researchers identified Great South Bay, a watery divide between Long Island and Fire Island, as a sand tiger nursery. It was discovered after a catch-and-release program noticed that young sand tigers who’d been fitted with tags were coming back to the same lagoon summer after summer. Other verified sand tiger nurseries include Massachusetts’s Plymouth and Duxbury Bays.

9. AQUARIUMS HAVE HAD A LOT OF SUCCESS WITH SAND TIGERS.

Tiger sharks and great whites are ill-suited for captivity, but sand tigers do well—given the right setup and proper care, sand tigers can live for decades in aquariums. One female named Bertha lived at the New York Aquarium in Coney Island for over 40 years before dying in 2008. (Attempts to breed sand tigers in captivity seldom work out, but some facilities like the now defunct Manly Sea Life Sanctuary in Australia had some success.)

To keep them in mixed-species tanks, staff members do their best to ensure that the sharks are well-fed at all times. At the Tennessee Aquarium, for example, the resident sand tigers are fed three times every week, with each individual receiving enough food per session to equate to around 2 percent of its body weight. This strategy discourages captive sharks from trying to eat live tankmates—although they may still nibble on the other fish every so often.

10. THE SHARKS LIKE TO CREEP AROUND SHIPWRECKS.

North Carolina’s outer banks are home to more than 2000 documented shipwrecks, earning it the nickname “Graveyard of the Atlantic.” Smaller fish are liable to transform ship remains into faux reefs, unwittingly attracting predatory sand tigers, who like to hunt on the sea floor. In the Graveyard of the Atlantic, divers have reported seeing over 100 sand tigers around a single wreck.

11. SAND TIGERS CAN HUNT COOPERATIVELY.

In 1915, American ichthyologist Russell J. Coles was monitoring fish off of Cape Lookout in North Carolina when he saw a gang of at least 100 sand tigers surround a school of bluefish. Working together, the sharks drove their victims into very shallow waters and then attacked them. On another occasion, a group of sand tigers near New South Wales started flailing their tails about like bullwhips, producing cracking noises that the sharks used to corral some yellowtail kingfish into a tight, vulnerable cluster—just in time for lunch.

Middle School Student Discovers Megalodon Tooth Fossil on Spring Break

iStock.com/Mark Kostich
iStock.com/Mark Kostich

A few million years ago, the megalodon was the most formidable shark in the sea, with jaws spanning up to 11 feet wide and a stronger bite than a T. Rex. Today the only things left of the supersized sharks are fossils, and a middle school student recently discovered one on a trip to the beach, WECT reports.

Avery Fauth was spending spring break with her family at North Topsail Beach in North Carolina when she noticed something buried in the sand. She dug it up and uncovered a shark tooth the length of her palm. She immediately knew she had found something special, and screamed to get her family's attention.

Her father recognized the megalodon tooth: He had been searching for one for 25 years and had even taught his three daughters to scour the sand for shark teeth whenever they went to the beach. Avery and her sisters found a few more shark teeth that day from great whites, but her megalodon fossil was by far the most impressive treasure from the outing.

Megalodons dominated seas for 20 million years before suddenly dying out 3 million years ago. They grew between 43 and 82 feet long and had teeth that were up to 7.5 inches long—over twice the size of a great white's teeth. They're thought to be the largest sharks that ever lived.

Megalodon teeth have been discovered on every continent except Antarctica, but they're still a rare find. Avery Fauth plans to keep her fossil in a special box at home.

[h/t WECT]

Watch the Denver Zoo’s New Baby Sloth Cuddle Up With Its Mom

Denver Zoo
Denver Zoo

If you’re a sucker for itty, bitty, furry animals, then you’ll want to drop whatever it is you’re doing and check out this video of the Denver Zoo’s newest resident. Uploaded by The Denver Post, the video shows a week-old sloth clinging to its mother, and it’s almost too cute to handle.

The healthy baby, whose name and sex have not yet been determined, was born on April 11 to its proud sloth parents: 23-year-old Charlotte Greenie and 28-year-old Elliot. It also has an older sister, named Baby Ruth, who was born in January of last year. Dad and Baby Ruth are “temporarily off-exhibit” to give mom and her newborn baby the chance to rest and bond in their habitat—an indoor aviary that's part of the zoo's Bird World exhibit.

The baby belongs to one of six species of sloth called the Linne's two-toed sloth, which is native to the rainforests of South America and are not currently considered threatened. Unlike their distant relatives the three-toed sloths, two-toed sloths are mostly nocturnal creatures. They also tend to move faster than their three-clawed counterparts, although fast is putting it generously.

Like many things sloths do, the baby was slow to arrive. Zoo officials predicted that Charlotte would give birth as early as January, but the expected due date may have been a miscalculation.

“Sloth due dates are notoriously challenging to predict because sloths are primarily active at night and we rarely observe their breeding,” the zoo said in a statement. “Our animal care team closely monitored Charlotte for months to ensure that she and the baby were healthy and gaining the appropriate amount of weight.”

The baby is expected to cling to its mother for at least six months. Zoo officials say the best time to visit mom and baby is in the late afternoon, when Charlotte is more likely to be active.

[h/t The Denver Post]

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