Shark Facts That Might Surprise You

The 34th official Shark Week runs July 24-30 on the Discovery Channel and aims to increase conversation and education about these ancient marine predators that are essential to the health of the ocean. (Discovery Channel and CNN share parent company Warner Bros. Discovery.)
There are over 500 species of sharks. They are as diverse as the dwarf lantern shark, which is smaller than a human hand, and the whale shark, which can grow as long as a school bus, said marine biologist Michael Heithaus, professor and dean of the College of Arts, Sciences & Studies at Florida International University in Miami. Since there are so many unique species, some characteristics may be true for one species but not for another.
Sharks have been around for hundreds of millions of years, and while they continue to evolve, they are also in grave danger. Largely due to overfishing, shark and ray populations fell 71.1% between 1970 and 2018, according to a 2021 study published in the journal Nature.

Sharks have one of the longest lifespans compared to other animals.

According to a 2016 study published in the journal Science, Greenland sharks are the longest-lived known vertebrates on Earth. Researchers using radiocarbon dating have determined that the North Atlantic species probably lives on average for at least 272 years and often does not reach maturity until 150 years old.

Greenland sharks can live for at least 400 years, scientists have estimated.

Sharks are older than trees and dinosaurs

The earliest fossil evidence of sharks dates back 450 million years, meaning these creatures existed at least 90 million years before trees and 190 million years before dinosaurs.
Sharks have been around since before Pangea broke apart, said Catherine Macdonald, director of the Field School and lecturer at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. (There was a single gigantic continent called Pangea about 250 million years ago.)

Additionally, sharks have survived five mass extinctions, one of which wiped out around 96% of all marine life.

Sharks can be useful for our environment

Tiger sharks, one of Australia’s top predators, can help ecosystems respond to extreme weather events. The species’ prey, including green turtles, seabirds, and stingrays, avoid shallow waters, often seagrass areas. As a result, seagrasses can become bushy and create a safe nursery area for juvenile fish, shrimp and crabs, Heithaus said.
A tiger shark glides through Beqa Lagoon in Fiji.

Sea grass absorbs carbon from the atmosphere and uses it to build its body. When the seagrass dies, the dead material is buried in the sediments at the bottom of the ocean and the carbon is pulled out of circulation, Heithaus added.

Researchers are currently trying to determine if this phenomenon occurs for other species of sharks and in other places such as coral reefs.

“It looks like it’s not just tiger sharks,” Heithaus said. “It’s probably these larger species that play an outsized role in helping to shape the ecosystems of which they are a part.”

Shark pregnancies can last over 3 years

The reproductive patterns of sharks vary.

Scientists bring nearly 100 baby sharks to life through artificial insemination
On average, sharks give birth after 11 or 12 months of pregnancy, but some sharks, such as the frilled shark and the basking shark, can be pregnant for more than three years.
Some sharks, like mako sharks and bull sharks, give birth, while other sharks, like cat sharks, lay eggs, said Jasmin Graham, president and CEO of Minorities in Shark Sciences, based in Bradenton, Florida.
Long pregnancy times and the fact that some sharks take 10 to 12 years to reach sexual maturity, such as the great white, further impact populations decimated by unsustainable fishing practices.

Sharks don’t vocalize

Sharks are mostly silent creatures, as they have no organs to produce sound.

Instead of talking, sharks communicate through body language, such as zigzagging, jerking, and moving their jaws.

Sharks can smell electricity

Sharks have a sixth sense: they can pick up nanoscopic electromagnetic currents. This extra sense can help them navigate the ocean and find prey, or even a mate.

“The minute of electrical impulse that a prey’s brain sends to its heart to tell it to beat is detectable by sharks, allowing them to find hidden prey quite efficiently,” Macdonald said.

With this finely honed sense, sharks hunt sick and weak animals, playing a crucial role in maintaining the health of the marine ecosystem.

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