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Sharks stir up emotions in nearly everyone, but these incredible creatures are much more than just ruthless predators (and Hollywood icons). Recent research has uncovered astonishing survival tactics and extraordinary abilities that help them adapt to a rapidly changing environment.
Scientists have also encountered a series of remarkable firsts. From virgin births to centuries-long lifespans, sharks continue to reveal fascinating secrets about themselves. Along with these revelations, dangerous myths persist, some of which could threaten the survival of these ancient marvels.
10. Baby Scans for Whale Sharks
Ultrasounds are typically safe for doctors, but something unusual happened in 2018. The subjects of this study were the world's largest sharks. Whale sharks, non-predatory giants, are massive, easily surpassing the size of a bus. Despite their enormous size, whale sharks tend to vanish from sight, often diving 1,829 meters (6,000 ft) deep and embarking on long, mysterious journeys. This makes their breeding cycle an enigma. Understanding when and where they breed could be crucial to conserving this endangered species.
Fortunately, a group of whale sharks lingered around the Galapagos Islands, allowing biologists to scan 21 females. Over two weeks, waterproofed equipment was used to keep pace with the massive sharks and capture images of their 25-centimeter-thick (10 in) skin. None of the females were pregnant, and the mysteries surrounding their reproductive biology remained unsolved. However, valuable data was collected, including new observations, such as the discovery of ovaries with follicles.
An interesting finding from the study was that the sharks increased their speed when the ultrasound was turned on, but not when they were tagged. This indicated that the ultrasound was audible to the females.
9. The First Omnivorous Shark
A 2018 study astonished experts. Sharks typically conjure images of devouring raw, bloody meat. For years, scientists knew that one species, the bonnethead shark, consumed large amounts of sea grass. Initially, it was thought that these sharks were simply ingesting the plants by accident while hunting in sea grass meadows. But when grass made up 62 percent of their stomach contents, researchers began to question this assumption. Though it was believed to offer no nutritional value, the sea grass actually prevented the stomach from holding more food.
In order to study the sea grass-eating predators, a unique tank was created. Five bonnethead sharks were placed inside and fed sea grass marked with a special chemical signature. Their diet was composed of 90% grass and 10% squid. After three weeks, the sharks gained weight. To confirm this, a chemical tracer was used, revealing that the sharks absorbed more than half of the nutrients from the grass. This discovery made the bonnethead sharks the first known omnivorous shark species.
8. Ancient Shark Attack
The Natural History Museum of Los Angeles County houses the fossilized skeleton of a flying reptile. This pteranodon has a shark tooth embedded in its neck. Initially, visitors believed this combination was just a coincidence, but it led researchers to investigate further. The pteranodon species, which was discovered in Kansas, lived about 85 million years ago when the area was submerged under an ocean. The shark species involved was Cretoxyrhina mantelli, an extinct predator that likely grew to about 2.5 meters (8 feet) in length.
The study found that the shark’s bite was deeply embedded under a vertebra's protrusions, indicating a powerful jaw was at work. It seemed unlikely that a loose tooth had simply drifted into the pteranodon's remains before they fossilized together. The exact cause of the bite remains unclear. The shark might have scavenged the floating carcass of the pteranodon, as modern sharks are known to strike seabirds with great force. This suggests that the living pteranodon could have been floating on the waves like a seabird when the massive C. mantelli struck.
7. Jumping Giants
In 2018, a study set out to compare the great white sharks with basking sharks. At first glance, they seem vastly different. The great white is a notorious predator, feared by both people and seals alike. In contrast, the basking shark is a gentle giant, slowly filtering plankton from the water. But a surprising discovery near Ireland revealed that these slow-moving creatures, which can grow up to 10 meters (33 feet) long, are capable of leaping. Video footage even captured them breaching the surface with as much speed and height as the great whites, shattering the myth that they were simply docile, floating giants.
Video analysis and the use of recording devices attached to one individual basking shark showed just how inaccurate the old view was. This particular shark took only nine seconds and ten tailbeats to race up from a depth of 28 meters (92 feet). It then breached the surface at an almost vertical angle, clearing 1.2 meters (4 feet) above the water, staying in the air for about a second. To illustrate the significance of this discovery, one researcher commented, “It’s a bit like discovering cows are as fast as wolves.”
6. The Florida Survivor
In 2014, divers in a popular Florida location encountered a shocking scene. A male lemon shark was found impaled by a metal fish stringer, a tool typically used by anglers to keep their catch tethered. It appears that the shark ingested both the fish and the stringer, which then pierced through its stomach and skin. Remarkably, the shark not only survived but provided scientists with an unprecedented opportunity to observe how sharks can expel hazardous objects in a way previously unimagined.
In the following 14 months, the male shark was spotted 12 times, with each sighting showing greater progress in the expulsion of the metal. Initially, only a sharp point could be seen protruding from its body, but as time passed, the shaft became more visible. By the time the shark was seen again in 2016, the object had been completely expelled, leaving behind only a scar where the wound had been. Despite the deep injury, the lemon shark survived for over 435 days without infection and likely recovered from serious damage to its stomach and liver. This case marked the first evidence of sharks' incredible healing abilities taking place internally as well.
5. Sharks Get Cancer
There’s a hopeful myth circulating that sharks are immune to cancer. Sadly, this isn’t true. The scientific community has known for over 150 years that sharks are susceptible to the disease. Cancer has been documented in 23 different shark species, and in 2013, the first case of cancer in a great white surfaced. This particular shark was photographed in Australian waters, where it was found with a large tumor on its mouth, measuring 30 centimeters (12 inches) in both length and width.
The persistent misconception that sharks are immune to cancer has been fueled by the shark cartilage industry, which markets related products as a remedy for cancer. This industry, along with shark finning, contributes to the slaughter of around 100 million sharks every year. No scientific study has substantiated the claim that shark cartilage prevents or cures cancer. Furthermore, scientists argue that even if sharks were miraculously resistant to cancer, consuming their tissues would not provide any protection against the disease in humans. This myth is also harmful to cancer patients who, in their desperation, might abandon effective traditional treatments in favor of unproven shark-based products.
4. Right-Handed Sharks
In 2018, scientists explored an intriguing question: Can global warming influence whether sharks are left-handed or right-handed? This inquiry refers to directional preference rather than fin usage. To test this, Australian researchers collected 24 Port Jackson shark eggs. Half were placed in a tank that mirrored the temperature of the bay from which they were collected, around 20.6 degrees Celsius (69.1°F). The other half was incubated in a tank simulating future temperatures due to climate change, gradually heated to 23.6 degrees Celsius (74.5°F).
Half of the pups hatched from the warmer tank died within the first month. The surviving sharks were then tested for their “handedness.” They were placed in front of a Y-shaped partition and had to choose a path to reach food. While the sharks from the cooler tank showed no preference, those from the warmer environment consistently chose the right path. This behavior could be a remarkable adaptation. As warmer waters increase metabolic demands, sharks grow and process energy faster, which may lead to smaller brains. Automatically turning right in the face of a choice could be a strategy to conserve mental capacity.
3. 500-Year-Old Sharks
If there were a prize for the most peculiar creature, the Greenland shark would undoubtedly claim it. At first glance, this shark seems ordinary and unimpressive. However, its astonishing longevity reads like something straight out of a sci-fi novel. In 2016, scientists made the first attempt to measure the lifespan of this species. They collected 28 of these slow-moving Arctic sharks, all of which had already died due to fishing accidents and research vessels. One key observation was how slowly the sharks grow. The fact that some adults reach 4.9 meters (16 feet) hinted at their potential for long lives.
To narrow down their age estimate, researchers turned to radiocarbon dating. The ‘body part’ they chose for analysis was eye proteins formed at birth. Interestingly, radiocarbon dating usually carries a signature known as the 'bomb pulse,' which resulted from the nuclear tests of the 1950s and 1960s, releasing vast amounts of radiocarbon. The sharks in this study bore this signature, which allowed for a more precise calculation of their growth rates. Remarkably, some of the sharks could be over 500 years old. Even more astonishing, they only reached sexual maturity at 150 years.
2. Uterus-Switching Pups
Sharks are often seen as symbols of independence. In 2018, this trait was displayed in an extraordinary manner. It's already known that sharks sometimes consume their own siblings while still in the womb, or in this case, the unfertilized eggs. During an underwater ultrasound of a captive tawny nurse shark, scientists witnessed this 'pup-eat-pup' behavior firsthand. What truly surprised the researchers was the method behind it.
The tawny nurse shark has two uteri. Demonstrating its independent nature, the pups moved from one womb to the other to feast on the unfertilized eggs of their siblings. This not only makes the tawny nurse shark quite unique, but it also provides new insights into a 1993 documentary. In the film, a crew filmed a pregnant sand tiger shark and observed her pups switching between uteri through a hole in her side. Although the hole was caused by a wound and wasn’t entirely natural, this was the first recorded instance of such uterus-switching behavior among sharks.
Tawny nurse shark pups also exhibit some curious behavior. In an astonishing discovery, some embryos were observed poking their heads out of the mother's cervix, allowing them to make direct contact with the surrounding water before birth.
1. Pups Without A Father
Leonie, the zebra shark, moves gracefully through the Reef HQ Aquarium in Australia. For several years, she and her mate had produced multiple litters. When they were separated in 2012, her caretakers understandably believed that reproduction had come to an end. However, in 2016, Leonie laid three eggs, which later hatched. Initially, these triplets were assumed to have resulted from stored sperm. Yet, DNA tests showed that none of the males she had been in contact with years prior were the fathers. Instead, the pups were genetically identical to Leonie herself.
Before this discovery, asexual reproduction was not known to occur in zebra sharks. As a result, Leonie has become the first recorded case of a shark shifting from sexual reproduction with a mate to the self-sufficient, no-male-needed form of reproduction known as parthenogenesis.
Parthenogenesis occurs when an egg cell acts in place of sperm. While more commonly observed in plants and invertebrates, instances of vertebrates that normally require a mate reproducing asexually are becoming more frequent. Creatures such as Komodo dragons, vipers, and even chickens have been known to reproduce without males. While this may seem unusual, it's a positive turn for zebra sharks, as they are classified as an endangered species.
