Welcome back to another Finn Friday! Today we are going to dive into the mysterious world of the Greenland shark. The Greenland shark is, yet again, one of my favorite shark species (I mean, basically all of them are at this point if I’m being honest). Its claim to fame is being the longest-living vertebrate (that we know of). Some of them can reach 500 years old (that’s over TWICE as old as the United States!). Now let's learn all about these ancient sharks!
Where do they live?
Greenland sharks LOVE the cold. They prefer water that is around 28-44 degrees Fahrenheit. You can find them cruising around in the Arctic Ocean and the North Atlantic. They tend to keep to deeper water, usually more than 200 meters down! They can sometimes be seen at the surface during the winter months, but are known to go down as far as 2,200 meters during the summertime.
How long do they live?
Like I mentioned earlier, based on radiocarbon dating of isotopes found in their eye lens, scientists believe they can reach ages up to 500 years old. Because Greenland sharks don’t come into contact with humans often, we don’t know much about what their average age might be. We do know, though, that they don’t become reproductively mature until around 156 years old. We can also tell that they are a long-lived species because they also grow very slowly. They reach up to 7 meters in length (3-5 meters on average), but they only grow around 1 centimeter per year. So, long story short, they live a REALLY long time.
What do they eat?
Like most sharks, the Greenland shark loves to eat fish. Some of their favorites are herring, halibut, and salmon. They have also been known to eat marine mammals, like orcas or seals. Surprisingly, scientists have also found reindeer and polar bears present in stomach contents!
What do they like to do?
Because Greenland sharks are so secretive, we don’t know a whole lot about their day to day behavior. We know they are a top predator, like most shark species. They are also pretty slow swimmers, typically cruising around at about 1.9 miles per hour. One fun fact, though, is that the only recorded possible ‘attack’ by a Greenland shark on a human dates back to 1859.
Now for a deeper dive into my favorite bit, how old they are! It is super rare for vertebrates to reach ages as old as the Greenland shark. So, how do they do it? What about them lets them reach such mind-blowing ages? Well, we have a few guesses as to what contributes to their multi-century lifespan. The main thing scientists think leads to their long lives is that they live in really cold water. The cold water slows down their growth and metabolism. A slower metabolism means that, over the same amount of time, there will be less damage to their various tissues than an animal with a faster metabolism, like humans. Also, in a recent study on nematodes (a type of roundworm), cold water was shown to activate anti-aging genes. These anti-aging genes helped the animal get rid of DNA-damaging molecules and fight off infections, among other things, that help extend their lifespan. Because these molecules are conserved across the animal kingdom, meaning they are found in a wide range of species, it is safe to say that they probably play a role in the Greenland shark’s extended lifespan too.
Conservation status:
According to the IUCN Red List, the Greenland shark is listed as near threatened. As far as sharks are concerned, that's pretty good. Like most oceanic animals, their biggest threats are pollution and overfishing.
Thank you for learning with me! I don’t know about you, but I can’t wait for scientists to learn even more about these mysterious creatures. Part of why I love science so much is that there is always something new to learn! What questions do you have about the amazing Greenland shark? Leave them below!
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