A new study reveals that Greenland Sharks can live between 200 and 500 years. Native to the Arctic and North Atlantic Oceans, these sharks are known as one of the largest shark species and the longest-living animal ever.
This Shark is a Gentle Giant
With no documented cases of attacking humans, the Greenland Shark is a gentle giant. They are one of the largest sharks in the world, with the largest of its kind measuring 21 feet in length and over 2,000 pounds in weight. Typically, they are closer to 900 pounds and 18 feet.
Age is but a (REALLY BIG) Number
Greenland Sharks are known as the world’s longest-living vertebrates. The oldest living Greenland Shark is estimated at roughly 400 years old. A study of 28 female sharks revealed a lifespan of at least 272 years. The estimated ages of the two largest sharks in the study were between 335 and 392 years old. The study suggested that the average lifespan of a Greenland Shark is 390 years.
Live Long, Grow Slow
The Greenland Shark’s long lifespan is said to be related to its slow metabolism. These sharks are also slow swimmers, with an average pace of 0.3 meters per second, giving them the nickname “sleeper sharks.” They have extremely low energy needs and grow at an extremely slow rate, taking up to 150 years to reach full maturity. This is likely due to the cold and deep waters they live in.
Determining How Old a Shark Is
Greenland Sharks cannot be aged similarly to other shark species. Sharks are typically aged by counting the growth bands on their fin spines or vertebrae (similar to rings on a tree’s trunk). However, Greenland Sharks have no fin spines, and their vertebrae are too soft to form growth bands.
Aging the Greenland Shark
Due to the Greenland Shark’s differences from other shark species, scientists previously aged them based on their growth over time. The Greenland Shark grows less than one centimeter annually and can reach up to six meters (21 feet) in length. Therefore, scientists calculated that their growth is extremely slow, and their lifespan is extraordinarily long.
Carbon Dating
A recent study found a new way to age Greenland Sharks – carbon dating. Scientists now use a protein found in the shark’s eye, which is formed before birth and does not degrade with time. The lenses of the shark’s eye are metabolically inactive, and new layers grow throughout the shark’s life. In the carbon dating process, scientists measure how much carbon-14 – a carbon isotope, the lens has.
Carbon-14
This radioactive isotope occurs naturally on Earth, but levels change yearly. Thus, scientists can see during which periods the shark was alive by the carbon-14 signatures in the eyes when carbon dating. For example, scientists studying a group of 28 shark eyes in 2009 found that the smallest shark was born after the “bomb pulse” of the 1950s and 1960s, while the larger sharks were born before it.
How Accurate is Carbon Dating?
Carbon dating only provides an estimated age, and the results of this type of testing are not definitive. However, scientists are refining this method to provide more accurate measurements.
The Greenland Shark’s Lifestyle
As previously mentioned, Greenland Shark are slow movers, however, they eat a variety of species such as seals, fish, squid, seabirds and even terrestrial mammals like horses and reindeer. They live in warm (for the Arctic), inshore waters in summer, and deep, cold waters in winter. They are the only sharks that can survive the Arctic’s cold waters year-round and are thus found in the northern Atlantic and Arctic Oceans. However, they have been known to travel south to the North Sea and the Eastern Seaboard of the United States.
Lifecycle
Not much is known about how Greenland Sharks reproduce, but females are estimated to reach full sexual maturity when they are about 13 feet long. Females retain their eggs inside their bodies until they hatch and produce an average of 10 offspring at a time. Much like other shark species, Greenland Sharks are independent from birth.
Greenland Sharks vs Humans
Given that Greenland Sharks are known to live in areas of the ocean where we do not normally swim, they rarely interact with humans. However, humans have not been as kind. Greenland Sharks have been hunted for their liver and skins, which were used in making oil for lamps and engines. Their skin was used in leather production. Greenland Sharks are not hunted as food because their meat is poisonous if consumed raw. However, it is fermented and repeatedly boiled and used as meat for sled dogs.
Conservation
The International Union for Conservation of Nature (IUCN) has estimated that Greenland Shark populations are down by more than 30-49%. Due to their long lifespan, Greenland Sharks are particularly susceptible to overfishing. Additionally, they are often accidentally caught as bycatch, further decreasing their numbers. The IUCN has placed them on the protected species list as of 2020.
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