A Greenland shark does not look built for speed. It moves through cold northern water with a blunt body, a slow tailbeat and the unhurried rhythm of an animal whose life is measured less in seasons than in centuries.
That impression is not only aesthetic. In a 2012 study in the Journal of Experimental Biology, Yuuki Watanabe and colleagues measured Greenland sharks swimming at an average cruising speed of about 0.34 metres per second, with a maximum tailbeat frequency lower than other fish of comparable size. Converted roughly, that average is a little over 1.2 kilometres per hour.
Most people walking down a street would be faster. A commonly cited adult preferred walking speed is around 1.4 metres per second, or about 5 kilometres per hour, though it varies with age, body size and setting. A 2011 review in Gait & Posture placed usual adult walking speed close to that range across many studies.
The shark’s slowness would already be enough to make it memorable. But the deeper surprise is time. The age and maturity numbers rest mainly on one direct ageing study, not a neat birth record. The finding is strong enough to take seriously, but it should be read as an estimate with wide uncertainty, not as a precise birthday.
In 2016, Julius Nielsen and colleagues reported in Science that Greenland sharks may be the longest-lived vertebrates known. Using radiocarbon dating of eye-lens tissue from 28 female sharks, the team estimated that the largest individual in the sample was about 392 years old, with a range of plus or minus 120 years. The same paper estimated sexual maturity at around 156 years.
The slow shark problem
The Greenland shark, Somniosus microcephalus, belongs to the sleeper sharks, a name that suits its public reputation almost too well. It lives in cold North Atlantic and Arctic waters, often in dim or deep habitats where direct observation is difficult.
The Florida Museum’s species profile describes the Greenland shark as a large, heavy-bodied species associated with cold, deep water, and notes that it has been found with fish, seals and other animals in its stomach. That combination creates a puzzle: how does such a slow swimmer feed on animals that should easily outpace it?
Watanabe’s 2012 study sharpened the question. The researchers found that Greenland sharks were slow not only in absolute terms but also relative to body size and water temperature. They suggested that the sharks may capture sleeping seals or rely heavily on scavenging, though the exact balance of hunting and scavenging remains difficult to pin down.
That is the useful correction to the cartoon version. Slow does not mean harmless, weak or biologically simple. A slow shark can still be an effective predator and scavenger if it is adapted to the conditions around it. In freezing water, under low light, with prey that may sleep or sink, speed is not the only way to make a living.
How do you age a shark with no birthday?
Ageing a Greenland shark is not like ageing a tree. There are no convenient rings to count in a cut trunk, and the animals are too long-lived and remote for direct lifetime observation. Many fish can be aged using hard body parts such as otoliths, but sharks do not have the same bony ear stones.
Nielsen’s team used the eye lens instead. The inner proteins of the lens are laid down early in life and then remain unusually stable. By measuring radiocarbon in those tissues, the researchers could use the mid-20th-century “bomb pulse” from nuclear testing as a time marker, then combine the carbon data with shark length and growth modelling.
The method produces estimates, not exact ages. That is why the 392-year figure should not be rounded into certainty. The oldest shark was estimated to be roughly four centuries old, but the uncertainty range was large enough to matter. Even so, the lower end of the range still leaves an animal of extraordinary age.
The maturity estimate may be even more important for the species’ future. A female that may not reproduce until around 150 years old belongs to a life-history pattern almost opposite to fast-breeding animals. If adults are removed, replacement is slow. Very slow.
Centuries change the conservation question
Long life can sound like resilience. For a population, it often means the opposite. Species that grow slowly, mature late and produce new adults only after long delays can be badly affected by fishing pressure, even when the catch does not look large by ordinary standards.
The IUCN Red List currently lists the Greenland shark as Vulnerable. Historically, it was targeted for liver oil, and today it can still be caught incidentally. Climate change and shifting Arctic ecosystems add further uncertainty, especially for an animal whose life cycle is so long that rapid environmental change can compress several shark generations into one human lifetime.
This is the uncomfortable edge of the four-century fact. An individual shark may have lived through the rise of modern science, industrial whaling, steamships, radio, satellites and genomic sequencing. But a single fishing event can end that history in minutes.
Why the Greenland shark keeps pulling us back
The Greenland shark attracts attention because it rearranges scale. Human beings are used to thinking of vertebrate lives in decades. A dog lives one kind of time, an elephant another, a bowhead whale another still. The Greenland shark stretches that timeline until early modern history begins to feel recent.
It would be easy to turn the shark into a symbol and stop there. But the biology is more interesting than the symbol. Its slow swimming raises questions about hunting, metabolism and cold-water physiology. Its lifespan raises questions about growth, tissue maintenance and ageing. Its late maturity raises questions about how to protect animals whose reproductive timelines make human planning look impatient.
The cleanest way to state the Greenland shark’s strangeness is still the plain one. It swims so slowly that a person could usually walk faster. It may wait around a century and a half before reproducing. And one individual in the best-known ageing study was estimated to have lived for roughly four hundred years.
That is not a fossil story. It is not ancient life sealed in stone. It is a living fish moving through cold water now, carrying a version of time that makes the surface world seem almost frantic.
