8 Intriguing Shark Behaviors That Will Amaze You

Sharks have roamed the Earth for more than 400 million years. Found in every ocean and some rivers, they play a crucial role in maintaining a healthy ocean ecosystem—by regulating the food chain and promoting biodiversity. Sharks even help protect carbon-storing sea meadows by hunting the sea turtles that feed on seagrasses.

Although some shark behaviors might appear strange, they have evolved for specific survival reasons. Below are eight of the most surprising actions and how they contribute to sharks' success.

1. Sharks start hunting before they’re even born.

Sharks don’t all reproduce the same way; some lay eggs, while others give birth to live young. Live-bearing species, such as the great white, mako, tiger, and bull sharks, have an edge over egg-laying sharks: They start developing their hunting instincts even before birth.

A female sand tiger shark has two uteri and produces multiple eggs. Research has indicated that approximately 10 eggs get fertilized, while the rest are consumed by the stronger embryos. The developing embryos begin hunting once they reach about 2 inches long, feeding on the unfertilized eggs for nourishment. As they grow, they turn on their weaker siblings. This phenomenon, known as embryophagy, involves the baby sharks swimming from one uterus to the other to seek out prey until only the two strongest survive.

Embryophagy offers several advantages for the pups. It sustains them during their 9 to 12 months in the womb, helping them grow larger and healthier, which boosts their chances of survival at birth.

It also eliminates the weaker sharks from the gene pool. The female sand tiger shark mates with multiple males, resulting in embryos from different fathers. However, research shows that in 60 percent of the litters, the two surviving pups share the same father. This ensures that the genes of weaker fathers don’t pass on, while the stronger father’s genes are carried by the two surviving pups. This process also ensures that the baby sharks enter the world as fully equipped hunters.

2. Adult sharks can be cannibalistic as well.

Many sharks participate in cannibalism, particularly when one shark is injured. A 2016 study revealed that the extinct Orthocanthus, which lived 300 million years ago, consumed their own young when other food sources were depleted. Today's lemon sharks appear to favor the tangled roots of shallow mangrove forests as a nursery, protecting their young from both larger predators and other lemon sharks.

Cannibalism may seem like an odd behavior for an animal aiming to survive, but it's a crucial strategy to ensure the survival of the species. It's not just a source of food, but it also promotes the survival of the strongest individuals. Fortunately, sharks are not driven by sentimentality.

3. Unborn sharks have the ability to detect danger.

Surviving before birth is just as challenging for egg-born sharks—and some species have evolved strategies to safeguard themselves even before birth, as a 2013 study on bamboo sharks revealed.

Egg-laying sharks place their offspring inside protective casings (often called mermaid’s purses) that anchor to plants with long tendrils. These pouches help conceal the embryos' movements and scent as they develop. Towards the end of the gestation period, the cases open slightly to expose the embryos to the ocean's salty waters. At the same time, the baby sharks’ electrosensory systems mature, enabling them to detect their surroundings, including the electronic signals of potential predators. Juvenile bamboo sharks are naturally wired to interpret these signals and respond by holding their breath, curling into balls, and freezing to avoid being detected.

The authors of the study suggest that this behavior could be leveraged to create electronic devices that repel sharks. Every year, fishing nets unintentionally kill millions of sharks (and other marine creatures), so adding such technology to nets could protect not only bamboo sharks but all elasmobranchs.

4. Sharks have a knack for spying on you.

Spy-hopping, a behavior where a sea creature lifts its head above the water, is most commonly linked to whales. Though uncommon in sharks, a few species are known to raise their heads and scan the surroundings.

Some sharks will elevate their head vertically above the water, while others glide along the surface with just their eye peeking out. In both instances, spy-hopping serves to gather information, possibly to locate prey, but the action itself is non-aggressive. A shark approaches the surface calmly, and might repeat this several times without displaying aggression.

Great white sharks excel at spy-hopping, especially near boats that use chum to lure them in. Studies on oceanic whitetip sharks suggest that these fish can utilize their exceptional sense of smell above the water's surface to detect food from afar. It’s also possible that the sharks are simply inquisitive.

5. Some sharks leap out of the water.

Breaching is another behavior that may seem counterintuitive for an animal that relies on water to live, but several species, such as great white, basking, and bull sharks, leap from the water at incredible speeds. It’s an awe-inspiring sight, with some sharks completely clearing the water for several seconds thanks to the force they generate while swimming. The record is held by a great white known as Rocket, who jumped 15 feet out of the sea.

Breaching often stems from hunting. Snaring a swift seal is challenging, so sharks have learned that an ambush is their best tactic. Using the dark waters below as cover, a great white can silently approach a seal, launch upward at speeds of around 36 feet per second, and catch the seal before it has a chance to flee. The breach is the explosive result of this sudden upward movement.

However, breaching isn't only for hunting. Basking sharks, which don't need to leap to catch prey, still engage in breaching. This behavior could be linked to courtship rituals or used by male sharks to assert dominance. The dramatic splash produced by the breach may serve as a warning or communication signal to other sharks. Environmental factors like marine pollution, water temperature fluctuations, increased salinity, and the desire to remove parasites may also trigger breaching.

6. Sharks will walk away from danger.

The epaulette shark has developed a survival tactic that larger sharks can only dream of: calmly walking away from peril.

The behavior was first recorded in 1995 by researcher Peter Pridmore, but it wasn’t until a 2015 BBC documentary filmed at the Great Barrier Reef that the world took notice. The epaulette shark resides on the seafloor off the coasts of Australia and New Guinea, but when the tide recedes, many become stranded on the reef in waters reaching over 85°F. They’ve evolved the ability to conserve oxygen and use their pectoral and pelvic fins to walk distances of up to 100 feet. By crawling across the sunlit coral, they can find small pockets of water to replenish oxygen until the tide returns.

Since 1995, eight additional walking shark species have been identified, including the Halmahera epaulette shark, discovered in Indonesia in 2013, and four others found during a 2020 study of the Hemiscyllium genus. A 2022 study concluded that this skill is becoming increasingly important in the face of climate change, suggesting “this species has developed adaptations that allow it to cope with some, though not all, of the challenging conditions expected in the 21st century.”

7. Sharks can eject their stomachs.

Unfortunately, sharks have been discovered with their stomachs containing various non-edible objects, including tires, a chicken coop, and even an unexploded bomb. This issue is escalating as the world’s oceans continue to be polluted with waste.

One way sharks deal with this is through stomach eversion—essentially the ability to vomit out their stomachs, cleanse them, and then swallow them again, all in a split second. A 2005 study of a Caribbean reef shark recorded two instances of stomach eversion lasting 0.28 and 0.40 seconds, with a 1.52-second gap in between. The study concluded that “its function might be related to the removal of indigestible food particles and mucus from the inner lining.”

A 1990 study of captive sharks revealed that they are capable of eversion of their lower intestine through their cloaca, although this process appears to last significantly longer than stomach eversion. A recent paper published in the Journal of Ethology reported that a shark can swim for over two minutes with its intestines dangling from its body, as shown in a video of a captive tiger shark.

Eversion comes with its own dangers in the wild. As part of the Journal of Ethology study, researchers observed an oceanic whitetip shark being pursued by smaller predators, who were “taking advantage of ejected digested material” and attempting to bite the exposed organ.

8. Sharks have been known to live inside volcanoes.

Sharks are present in nearly every environment on Earth, but one place where they may surprise people is within the heart of an active volcano.

The Kavachi volcano, situated beneath the Pacific Ocean near the Solomon Islands, is notorious for its regular eruptions, releasing sulfur, carbon dioxide, ash, and rocks into the water, turning it an orange hue. The caldera is too toxic for humans, and the water is scalding hot—yet two species of sharks have made this harsh environment their home. In a 2015 study unrelated to sharks, a robotic submersible discovered hammerhead and silky sharks swimming and hunting in the volcano’s acidic waters.

Though the exact mechanisms remain unclear, sharks' evolutionary traits have enabled them to survive all five major mass extinction events that wiped out countless other species. These adaptations include early-warning systems that allow them to instinctively flee dangerous areas ahead of eruptions.

Incredibly, these active volcanoes provide the sharks with significant protection from larger predators, making them a much safer habitat than oceans populated by humans.