Imagine that you’re swimming in the ocean and—oh no!—you spot a shark! That would be scary for anyone. We’re used to thinking about sharks as vicious killers who would attack a victim quickly. But what if the shark you spot is not fast, but slow? Is that possible? Let’s WONDER together—what type of shark is the slowest?

As it turns out, the slowest shark is the Greenland shark. The Greenland shark is a kind of sleeper shark. It lives in very cold waters near the Arctic Ocean and the North Atlantic Ocean. In these icy waters, the Greenland shark swims only about one mile per hour. That is slower than many human swimmers! The fastest shark, the shortfin mako shark, can swim up to 45 miles per hour. 

Why is the Greenland shark so slow? Scientists think that it all has to do with their cold water home. When fish are in cold water, their bodies slow down. Their bodies become cold and their muscles cannot work as well. They cannot move as fast as they can in warm water. Human beings do not experience this because our bodies stay warm even in cold weather—if we’re staying safe, that is!

Are you WONDERing if there is anything else unique about the Greenland shark? There sure is! Not only is the Greenland shark the slowest shark in the ocean, it’s also the one that lives the longest. In fact, Greenland sharks don’t even become full adults until they are about 150 years old! Scientists have learned that they live about 500 years. That is longer than any other vertebrate animal—any animal with bones.

How can Greenland sharks live so long? For a long time, scientists didn’t really know. It is hard to study Greenland sharks because they are difficult to find! They live in very deep, very cold water. Recently, though, scientists have learned more about how Greenland sharks live. They learned that these sharks eat small amounts of food for their size. A Greenland shark weighing 500 pounds would need less than 7 ounces every day! That is less than half a pound of food.

They need small amounts of food because they use up energy very slowly. The way we use up energy from food is called metabolism. Greenland sharks have an extremely slow metabolism. This makes sense, because scientists already know that animals with slow metabolisms tend to live longer.

Because Greenland sharks move so slowly, scientists still aren’t sure how they catch their prey. We know that these sharks sometimes eat much faster animals, such as seals. Some think that Greenland sharks are able to sneak up on seals while they sleep and catch them.

As scientists continue to study these unusual animals, we hope to learn more about them. What questions do YOU have about Greenland sharks? Maybe one day you will help answer them!