11 Facts About Bull Sharks

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Compared to sharks like the hammerhead (with its oddly shaped skull) and the goblin (with its projectile mouth), the bull shark (Carcharhinus leucas) looks rather generic—but this predator can swim thousands of miles upriver, hunt baby hippos, and take over the occasional golf course.

1. BULL SHARKS HAVE A VERY STRONG BITE.

In 2012, scientists compared the bite strengths of 13 different sharks and shark-like fish and found that an adult bull shark can theoretically close its jaws with just under 6000 newtons of force at the back of its mouth and over 2000 newtons at the front. (Humans chomp with a maximum force of around 900 to 1300 newtons.) So proportionately, the bull shark has the strongest bite of any shark whose jaw strength has been measured. Nobody knows exactly why the shark evolved such a powerful mouth, but it may have something to do with its diet: Bull sharks eat everything from oysters to turtles to other bull sharks, and their herculean jaws might make it easier to tear through a wide range of shells, scales, and skins.

2. THEY THRIVE IN FRESH WATER.

All organisms need a specific salt-to-water ratio within their bodies. This presents a challenge to aquatic life forms—when they absorb too much salt, their cells get dehydrated, but if they take in too much fresh water, the cells get bloated and some of the chemicals inside their bodies may become fatally diluted.

Fish have evolved a couple of tricks to cope with the problem, one of which involves pee. Excess salt is removed from the bloodstreams of oceangoing fish by the kidneys and then flushed out during the urination process. Freshwater fish do the opposite: Their pee contains very little salt and their bodies retain a higher concentration of the substance.

Most fish have no control over how much salt gets removed by their kidneys, which is one reason why many species can only survive in either fresh or salt water. But bull sharks can actually regulate the amount of salt that goes into their pee, which means they can live in both environments. When they swim in the ocean, their urine is highly saline. And as they venture into fresh water, the kidneys work hard to retain salt—thus producing watery, diluted urine. (Bull sharks also use their rectal glands and livers to maintain the proper balance between salt and water.)

3. A BULL SHARK WAS ONCE CAUGHT NEAR ALTON, ILLINOIS.

In 1937, two fishermen captured a 5-foot bull shark more than a thousand miles up the Mississippi River—as far north as this species is known to travel up that river. Given their high tolerance for fresh water, it’s no wonder that bull sharks do well in river systems. One specimen was found swimming in the Amazon River about 2485 miles away from the ocean; they also frequent Africa’s Zambezi River and the Ganges River in south Asia.

4. NOT EVEN HIPPOS ARE SAFE FROM BULL SHARK ATTACKS.

In their trips upriver, bull sharks encounter some of the fiercest predators on earth: In Australia, an 18-foot-long saltwater crocodile named Brutus was once photographed devouring a small bull shark, and in African waterways the sharks have run-ins with hippos. The mammals generate a lot of poop, which attracts small fish that bull sharks eat—so it’s not at all uncommon to see a bull shark or two creeping around a pod of hippos.

The two species don’t always get along. Bull sharks do prey on young hippos on occasion, and adults are sometimes bitten as well—though these attacks might be accidental (in murky, poop-filled water, bull sharks probably mistake hippo legs for fish). Whatever the case may be, large hippopotamuses are adept at fending off bull sharks.

5. UNLIKE GREAT WHITES, BULLS CAN DO WELL IN AQUARIUMS.

No one has been able to keep a great white in captivity for much longer than six months. Bull sharks, however, can live in captivity for 25 years or more. In North America, you can see them at the Oklahoma Aquarium, which houses 10 bull sharks in a nearly 500,000-gallon tank.

6. LAKE NICARAGUA’S RESIDENT BULL SHARKS WERE ONCE THOUGHT TO CONSTITUTE A NEW SPECIES.

Scientists used to think that the large-bodied sharks that periodically attack locals in Lake Nicaragua—the biggest lake in Central America—represented their own, distinct species. A popular hypothesis claimed that Lake Nicaragua must have started out as a bay in the Pacific Ocean that closed up as time went by, trapping some sharks inside that evolved into a brand new species—the so-called “Lake Nicaragua shark,” which ichthyologists called Carcharhinus nicaraguensis.

But Lake Nicaragua isn't cut off from the ocean at all, and scientists eventually determined that “Lake Nicaragua Sharks” are really just bull sharks that were entering the Rio San Juan from the Caribbean and making their way to the lake [PDF].

7. AN AUSTRALIAN GOLF COURSE IS INFESTED WITH THEM.

At the Carbrook Golf Club, located near Brisbane, Australia, tee time sometimes comes with teeth. The course is next to the Logan River, which flooded several times in the 1990s. At some point, newborn bull sharks were probably swept into the brackish, landlocked lake that sits beside tees 12 through 15, and were trapped there when the Logan receded. The lake is spacious (about 50 acres, or the size of Grand Central Terminal) and stocked with fish—good news for the sharks.

The first shark fin sightings were quickly dismissed. “Our members have a tendency to drink a little bit while they play so we really just put that down to too much alcohol,” general manager Scott Wagstaff told National Geographic. But by 2003, there were photos, and a 2011 YouTube video taken by Wagstaff went viral. According to the club’s website, “there are between 6 and 12 sharks” in the lake; the biggest is roughly 9 feet long. It’s also likely that they are breeding.

Carbrook Golf Club celebrates their cartilaginous guests: “Shark Lake Challenge” tournaments are held on the last Wednesday of every month and a stylized shark fin adorns the club logo. For obvious reasons, ball retrieval has been prohibited.

8. BITING IS A PART OF MATING.

Male bull sharks become sexually active at 14 or 15, but females don’t start reproducing until they're 18. Female bull sharks of reproductive age have scars behind their skulls: A male bites his partner to hang on during coitus (a behavior that appears to be common), then uses one of his claspers—a pair of fin extensions located under the pelvic area—to insert sperm into her cloaca.

Following a 10- to 11-month gestation period, the female will give birth to a litter of pups. Newborns typically range between 22 and 32 inches long.

9. ONLY TWO OTHER SHARK SPECIES BITE HUMANS MORE OFTEN.

All types of shark-on-human attacks are ultra-rare—you’re more likely to get struck by lightning. But the three shark species that are most commonly implicated in attacks on people are, in order, the great white shark, the tiger shark, and the bull shark. Bull sharks have been involved in at least 100 documented cases, and there's an explanation for that: They frequent shallow, coastal waters in tropical regions and often stray into brackish and fresh water—all places where humans can be found. In areas where the sharks can’t see very well, they may mistake humans for other, meatier prey.

Since bull sharks lack eye-catching markings or facial features, it can be difficult to identify them. This is why some experts wonder if bull sharks might have been responsible for certain attacks that were blamed on great whites, Ganges river sharks (Glyphis gangeticus), or other species.

10. A BULL SHARK MAY HAVE PARTICIPATED IN THE FAMOUS NEW JERSEY SHARK ATTACKS OF 1916.

On July 1, 1916, a 25-year-old swimmer was bitten by a shark off the coast of New Jersey's Long Beach Island. Though a lifeguard managed to rescue him, the man died of blood loss. Five days later, a bell captain lost both legs in a shark attack near Spring Lake. He too died. Farther north, a boy and an adult man were killed by a shark in Matawan Creek on July 12. Within 30 minutes, a teenager was bitten less than a mile downstream, but he survived.

All five attacks have historically been pinned on a single 8-foot-long great white that was captured and killed on July 14 in Raritan Bay, just a few miles away from the Matawan attacks. Inside its stomach were human remains. No subsequent shark attacks were reported in New Jersey that summer.

But the situation might not be so clear-cut: The two Matawan Creek incidents occurred 11 miles from the ocean, and great whites don't travel to shallow inland waters. Bulls are also more abundant off the Jersey shore than great white sharks are. That leads some experts, including explorer Fabien Cousteau, to conclude that a bull shark was the real culprit. Shark attack expert George Burgess still thinks the evidence points to the great white with a bellyful of body parts. It’s also possible that more than one shark committed the 1916 attacks.

11. NO, BULL SHARKS DON’T HAVE THE ANIMAL KINGDOM’S HIGHEST TESTOSTERONE LEVELS.

According to the internet, some books, and Grand Theft Auto, bull sharks are extra-aggressive because they have more testosterone than any other animal. In reality, very little research has been done on the subject of bull shark hormones. One study compared the testosterone levels in three bull sharks: The female had a low testosterone level (0.1 nanograms per milliliter), one of the males had only 2.7 nanograms per milliliter, and the other male had a ludicrously high testosterone level of 358 nanograms per milliliter—so the results were inconclusive. Bonnethead sharks and rainbow trout both have extreme testosterone levels, so in that regard, bull sharks aren’t special. At least they can still brag about their jaws.

Need to Cure of Case of Cabin Fever? Try Backyard Birding

Baltimore orioles are colorful spring migrants.
Baltimore orioles are colorful spring migrants.
Brittany Tande/iStock via Getty Images

No matter how many virtual tours and online classes you take, it's hard not to go a little stir-crazy after weeks of social distancing. If you're already sick of activities that require you to stare at a screen, consider seeking out real-life entertainment in your backyard. As Auburn Pub reports, the New York State Department of Environment Conservation is recommending that residents take up birdwatching during the COVID-19 pandemic. However, they stress that it's important to continue to practice social distancing.

Zoos, beaches, and even some national parks are currently closed to the public, but you don't have to travel far to get your daily dose of nature. Spring is in full bloom, and many bird species are currently in the midst of migrating from their winter homes down south to northern states. That means that even urban areas like New York City are becoming places for birds to nest and raise their young.

Local parks are great spots to observe birds while keeping your distance from others, but a trip off your property isn't necessary. If you have a backyard, or even just a tree on the street outside your home, you can watch birds from a patio, balcony, or through a window.

Birding is more than just a way to pass the time when activities are limited. A 2017 study from the University of Exeter found that being able to see birds around your home may reduce levels of stress, depression, and anxiety. If you use birding as an excuse to get out of the house, those benefits may be even greater as being outdoors in general has been shown to boost several facets of mental health.

If you're interested in using your time in isolation to get into birding, there are many resources online you can use. Watch this beginner's guide to birding and read these facts about the birds in your backyard before you get started.

[h/t Auburn Pub]

Beyond Tiger King: 10 Fascinating Animal Documentaries You Can Stream Right Now

A scene from Catwalk: Tales from the Cat Show Circuit (2018).
A scene from Catwalk: Tales from the Cat Show Circuit (2018).
Markham Street Films

By now, you've probably already binged Netflix's bewilderingly bonkers docuseries Tiger King (2020). If you're ready to dive deeper into the animal kingdom, there are plenty more documentaries out there. From wildcats to whales, these 10 films will take you on a cinematic adventure around the world, introducing you to captivating creatures and the people who love them.

1. The Tigers of Scotland (2017)

The Tigers of Scotland (2017) brings viewers as up close and personal as possible with a small but mighty feline: the Scottish wildcat. The film delves into the efforts to conserve the disappearing Highland tiger, as well as the history and mythology surrounding the UK’s only “big cat.”

Watch it: Netflix, Amazon, iTunes

2. Ghost of The Mountains (2017)

This 2017 Disneynature documentary will transport you to the world’s highest plateau in search of a family of snow leopards. These cats are famously tough to find, so Ghost of the Mountains offers viewers behind-the-scenes footage of what it’s like to track the elusive beasts.

Watch it: Netflix, Google Play, Youtube

3. Catwalk: Tales from the Cat Show Circuit (2018)

This delightful documentary takes you deep into the competitive cat show circuit. Both charming and at times cutthroat, the film brings viewers on a journey to see which of the many cool cats and kittens will be crowned Canada's top cat.

Watch it: Netflix

4. Kingdom of the White Wolf (2019)

Follow along as a National Geographic explorer and photographer embeds with a white wolf pack in the high Arctic. These wild wolves aren't used to seeing people, giving the filmmakers—and audience—an intimate window into the pack's daily lives and familial bonds. In addition to showcasing captivating footage of the animals, the three-part docuseries also features sweeping views of the starkly beautiful Ellesmere Island.

Watch it: Disney+, YouTube TV

5. Dogs (2018)

This docuseries, which highlights various dogs and their humans from around the world, celebrates the bond between people and their pups. But it’s more than just a montage of feel-good moments about humankind’s best friend: Each episode tells a broader tale about the human condition, crafting an emotional narrative that pulls at the heartstrings like a puppy tugging on a toy.

Watch it: Netflix

6. Dancing with the Birds (2019)

These birds will put your dad moves to shame. Watch the male avian performers shimmy, shake, and flash their feathers while attempting to woo their female mates. The documentary, narrated by Stephen Fry, offers a colorful look at the wonderfully wacky world of bird mating rituals.

Watch it: Netflix

7. Honeyland (2019)

This documentary follows Hatidze Muratova, one of the last wild beekeepers in a remote village in North Macedonia. She lives with her ailing mother, nurturing a traditional way of beekeeping passed down through the generations and striking a balance between making a living and maintaining ecological balance. But everything changes when a nomadic family settles nearby, threatening Muratova’s way of life. The resulting story is both sweet and stinging.

Watch it: Hulu, Amazon Prime, YouTube, Google Play

8. Virunga (2014)

This 2014 documentary highlights the park rangers fighting to protect the Congo’s Virunga National Park, home to the critically endangered mountain gorilla. As poaching and oil exploration threaten the park, the rangers and conservationists risk their lives to guard the rare creatures that inhabit it.

Watch it: Netflix

9. Harry & Snowman (2016)

In the 1950s, Harry deLayer bought Snowman, a run-down plow horse destined for slaughter, for just $80 at an auction. Within months, the two were taking the show jumping circuit by storm, launching both horse and rider to new heights. This documentary tells the story of the friendship the two developed, and chronicles their lives both in and out of the competitive spotlight.

Watch it: Amazon Prime

10. The Whale and the Raven (2019)

The waters around Canada’s Great Bear Rainforest are a haven for whales, who feed and find refuge in the quiet channels. With stunning visuals, this documentary highlights the tension of a community’s push to protect its wild places against the pressures of the ever-encroaching natural gas industry.

Watch it: Amazon Prime

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