DESPITE their popularity, there is much mystery surrounding the apex predators of the sea.
From the number of species to how they track their prey, sharks continue to surprise researchers with new puzzling traits.
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For starters, researchers are still discovering new species of sharks, despite having already identified more than 400 different species.
“The deep ocean is so vast, and we’ve spent so little time studying it, that it feels like every time a scientist goes out fishing or trolling or even goes to a fish market in an unfamiliar place, they’re a new shark species,” marine biology professor Christopher Lowe said Live Science.
Sharks are so flexible that scientists continue to do so discover new species in various habitats, especially in deep waters.
“In addition, sharks can vary wildly in size, from as small as a cigar (like the American bag shark) to as big as a school bus (like the whale shark,” Live Science reported.
Another mystery surrounding sharks is their strange migratory behavior.
Scientists aren’t entirely clear on how the predators swim around the vast and empty ocean without getting lost.
For example, great whites are known to swim all the way across the Indian Ocean, from Australia’s western coast to South Africa, a marine biologist said.
“It’s an enduring mystery how sharks make their way through the ocean, what environmental signals they use, and exactly how those signals are detected and integrated,” shark scientist Andrew Nosal told Live Science.
While we don’t know exactly how they migrate without getting lost, we do know that some sharks do indeed migrate seasonally.
It’s unclear how many species migrate consistently, but tracking studies show that the tiger shark has “partial migration, with some individuals tending to be house bodies and others tending to migrate,” Lowe said.
“And we don’t know why.”
Another endangered shark species, called Galeorhinus galeus, has a three-year migration, returning to its reproductive site every three years, according to Live Science.
However, it is still unclear why most sharks migrate and how they move through the ocean without getting lost.
When sharks don’t mysteriously travel great distances, they dive into deep waters for unknown reasons.
Trackers have documented the activity of many sharks, but when the fish dive to great depths, it’s difficult to track exactly what they’re doing, biologist Gregory Skomal said.
“We have a lot of data on white sharks showing that some of them go to the mid-ocean of Atlanta, wander and dive to depths as high as 3,000 feet every day,” Skomal told Live Science.
“But we have no idea what they’re actually doing there.”
Skomal did say they found some sharks in deep waters that appeared to be resting.
“I dare not say ‘sleep,’ because it is difficult for us to determine if and when these sharks are sleeping,” Skomal said.
It’s also unclear exactly where sharks fit in the underwater food chain.
The mysterious beasts are notoriously considered the ocean’s apex predator, but there are plenty of sharks that actually prey.
“It’s still a mystery exactly how sharks fit,” Nosal told Live Science.
“They are certainly important, and many species are indeed apex predators, but food webs are very complicated.”
The effects humanity has had on the ocean don’t help our study of sharks either.
Many habitats have been disrupted by overfishing, further obscuring their role in the ocean.
The intelligence of sharks is also ambiguous.
While they don’t have many folds in their forebrain, which is the part associated with decision-making and reasoning, they do have advanced development in their cerebellum that coordinates body movements, biologist Jelle Atema said.
One advanced aspect of sharks that is known is their sense of smell.
“In a 2010 study in the journal Current Biology, Atema and colleagues found that dusky smoothhounds turned to scents that were first stimulated in their noses, even if the second scent stimulation offered to them had a higher concentration,” Live Science said.
This shows that sharks can focus on a plume of scent even when a different, more concentrated scent appears in the crowded ocean.
The predators may also have detailed memories of the time and location where they found food, Lowe said.
Finally, scientists are still investigating whether sharks are social creatures.
Some sharks have been known to congregate, but it’s unclear whether this is due to environmental conditions or attraction to each other.
“Almost certainly it will be a combination of the two,” Nosal told Live Science.
“But we don’t really know to what extent sharks are social animals.
“There’s mounting evidence that they are, but the details are coming.”