Deep in the frigid waters of the arctic ocean hides a big and heavy creature shrouded in secret: the Greenland shark. This so-called “sleeper shark” is a massive predator and the longest-lived vertebrate that we understand of. It can mature to 6.4 meters (21 feet) and live over 500 years, and its harmful flesh enables it to survive at depths of listed below 2,200 meters (7,200 feet) and in freezing waters.
The strange Greenland shark. Image credits: NOAA.
But in spite of its massive size and durability, extremely little is in fact learnt about this evasive shark. Heres what we understand about it up until now.
A “living fossil” with bad eyesight
The Greenland shark also disproves a common myth about its kin: that sharks need to constantly swim. In reality, some sharks, consisting of the Greenland shark, can stay still for a time. The majority of sharks require to continuously swim in order to bring oxygen-rich water to their gills, but some can still breathe while stationary. The Greenland sharks circulatory system is specifically adjusted for this, which is especially important as the shark extracts oxygen while swimming at low speeds. Its special adaptations likewise allow it to survive in frigid waters, sometimes even listed below freezing (seawater does not freeze at fresh waters freezing point).
Possibly the most amazing thing about it is its incredibly sluggish growth rate and its exceptional life-span. They do not even reach sexual maturity up until theyre around 150 years of ages and they can live over 400 or even 500 years of ages, making them the longest-living vertebrates we understand of.
Sharks progressed some 450 million years earlier, before dinosaurs or even trees happened. The Greenland shark belongs to a household called sleeper sharks that are likewise ancient, over 100 million years old. The household is called Somniosidae, with Somnus being the Roman god of sleep.
Since they move so slowly through the water, theyre called sleeper sharks. The Greenland shark (Somniosus microcephalus), for example, usually swims at about 1.2 km/h (0.77 mph), with its fastest cruising speed only reaching 2.6 km/h (1.6 mph). This is slower than many seals and most fish also, which made numerous scientists question how they can even hunt.
In order to find out how long the sharks live, researchers tag sharks and regain them later on, determining their growth date. They likewise date them utilizing radiocarbon dating of crystals within the lenses of their eyes, but these approaches still have a variety of accuracy.
Despite their size and durability, nevertheless, very little is understood about their habits and ecology.
To make matters even worse for the shark, their vision is typically impaired by parasites that assault their eyes; its not unusual for Greenland sharks to have practically no vision at all– however they can still navigate utilizing their sense of smell. In fact, many Greenland sharks are thought to be infected with a parasite (a copepod called Ommatokoita elongata) that impacts their vision. Some researchers have actually even hypothesized that due to the fact that the copepod may be bioluminescent, it might form a mutualistic relationship with the shark by attracting victim, however this has not yet been confirmed.
A slow however formidable predator
While it is believed to be an apex predator, the Greenland shark might not be safe from other predators. In specific, sperm whales (Physeter macrocephalus) appear to hunt it. Greenland sharks have actually been observed to flee when they hear the calls of sperm whales, and scientists also found other inconclusive evidence that may hint that some sperm whales hunt Greenland sharks.
The Greenland shark doesnt appear to shy away from attacking large creatures, as was the case when one shark hunted a moose it almost choked on (the shark had actually to be saved by humans).
Image credits: Hemmint 1952.
Like many sharks, if it grabs on to something, it does not desire to let go. It has 48-52 teeth in its upper jaw and 50-52 teeth in the lower jaw– pointed teeth that assist the shark hold on to bigger food.
Its not clear if the Greenland shark hunts and kills all of these or simply eats their remains. The shark has actually been identified eating carrion and theres some speculation that this comprises a large percentage of its nutrition, however because the Greenland shark is so hard to observe in its natural environment, we dont understand for sure. Researchers believe that this scavenging behavior and its eager nose enables the shark to endure in freezing waters where theres not a lot of victim.
Despite its slow movement, the Greenland shark is a formidable predator– an apex predator at that. It feeds upon a broad variety of victim from fish and seals to whales and even reindeer or horses. A dissected Greenland shark even had the remains of polar bears in its stomach.
Greenland sharks outside Greenland
The gestation likewise takes a long time: one study estimated that theres a gestation period of 8-18 years but as is typically the case with the Greenland shark, this is objected to due to the fact that we just dont have enough observational details about it.
Not much else is understood about their recreation– we do not understand how numerous of these pups make it through or how (if) they are taken care of by their moms and dads.
In spite of its fierce track record and large range, the Greenland shark is not a danger to humans. Some cultures have misconceptions about people being attacked by Greenland sharks, theres no documented mention of this taking place (perhaps also because the shark chooses cold waters where people rarely swim). Likewise, the Greenland shark is usually shy and avoids contact with individuals.
The shark can likewise go extremely deep, being spotted in the Gulf of Mexico at a depth of 1,749 m (5,738 ft), where the water temperature level was 4.1 ° C( 39.4 ° F). The shark hardly ever appears to go lower than 1,500 m, but it doesnt avoid deep environments as it seeks its preferred cold water (− 0.6 to 12 ° C or 31 to 54 ° F) environment.
Although they do not appear to be really sociable, Greenland sharks can bring to life over 200 live puppies at one time according to some quotes (though other estimates are much more conservative and estimate around 10 puppies per pregnancy). The sharks are around 14 to 18 inches (35 to 45 centimeters) long when theyre born and, as mentioned, it will take them over a century till they can mature enough to produce offspring of their own.
Names can be tricking, and this is certainly one of those cases. The Greenland shark, a solitary animal rarely seen in groups, is a good long-distance swimmer and has actually been identified anywhere from eastern Scandinavia to the Caribbean.
The thought range of the Greenland shark.
Threats and preservation
A 1947 register of the species. Image credits: H. Dupond in Poll.
The main risk (or one of the main risks) faced by Greenland sharks is overfishing. Theyre typically captured as bycatch in commercial fishing operations, however often theyre particularly hunted, either in conventional medicine or as a delicacy in Iceland.
Currently, the species is thought about “near-threatened” however once again, we do not really understand much about the population because its so difficult to observe them in the wild.
Environment modification also positions a danger to them. Thousands of Greenland sharks are killed around melting ice every year, and as temperatures increase, more ice melts– and the more ice melts, the more routes are likewise opened for business fishing. Providing them prompt defense might be a much-needed lifeline.
Overfishing, both deliberate and unintended (an estimated 3,500 Greenland sharks are unintentionally captured as bycatch each year), is probably the greatest risk the Greenland shark is dealing with (and this is true of all sharks). The very same longevity that makes them so remarkable is likewise what makes them susceptible: because it takes them so long to become sexually active, and since they can live for so long, every captured Greenland shark can make a big difference for the population. Although its tough to approximate because they are so difficult to study, its estimated that Greenland shark populations have decreased by 30– 49% or perhaps more. This prompted the IUCN to change their evaluation from “Near Threatened” to “Vulnerable.” Many feel thats not enough.
The teeth of the Greenland shark.
Most biologists rejoiced when, at their annual meeting in Portugal, the Northwest Atlantic Fisheries Organization (NAFO) prohibited the retention of Greenland sharks in global waters. “It was a very long time coming, but not a long time in the life of a Greenland shark,” Sonja Fordham, president of Washington, D.C.-based Shark Advocates International, who went to the recent NAFO conference in Portugal, informed Mongabay.
The Greenland sharks skin is harmful due to the fact that it collects urea, an adjustment that enables it to survive in cold environments. Theres even an Inuit legend about this: according to misconception, an old female cleaned her hair in urine (a typical practice to kill head lice) and dried it with a fabric. The cloth flew out into the sea and ended up being the first Greenland shark. Another, more gruesome legend informs of a daddy who killed his child by drowning her, cutting her fingers as he did so. Each of the fingers went on to become a sea creature, consisting of one that ended up being the Greenland shark.
Greenland sharks are extensively considered the longest-lived vertebrates on earth. They grow at a slow rate, have a long gestation period, and it takes them a long time to recreate. All this makes the types susceptible to threats like overfishing.
At any rate, the meat of a Greenland shark is poisonous and not safe for consumption by animals or people. By boiling it in several changes of water and then drying and fermenting it for numerous months, people produce kæstur hákarl– fermented Greenland shark that is thought about a delicacy in Iceland, and is sometimes consumed in conventional Chinese medication.
” Theres still a lot we do not know about them: the number of they are, their abundance, their population structure, we have no idea where they go to mate, or where they go to have their pups. We do not know the number of pups they have or how often they recreate,” Brynn Devine, an Arctic fisheries advisor at Oceans North, informed Mongabay. “And that makes preservation planning particularly challenging because those are the things that you need to understand to comprehend how at risk a types is to things like bycatch.”
A mystery in the deep
Overfishing, both unintentional and intentional (an estimated 3,500 Greenland sharks are accidentally captured as bycatch per year), is most likely the most significant danger the Greenland shark is facing (and this is real of all sharks). Sharks are unexpected and marvelous creatures, and the Greenland shark is a worthwhile member in the Pantheon of shark species.
Scientists dont truly know why these sharks live so long, where they roam, whats their relationship to other predators, and many other concerns.
Sharks are majestic and unexpected animals, and the Greenland shark is a worthy member in the Pantheon of shark types. Regardless of researchers finest efforts to study it, it remains a remarkable and mysterious creature of the deep. With additional research and conservation efforts, we can want to better understand and protect this ancient predator of the oceans and with it, its links to the remainder of the environment.
Weve checked out so little of the oceans, it would be a shame to ruin these animals prior to we get an opportunity to understand them.
The Greenland shark is part of a family called sleeper sharks that are likewise ancient, over 100 million years old. The Greenland shark likewise disproves a common myth about its kin: that sharks need to constantly swim. Greenland sharks have been observed to flee when they hear the calls of sperm whales, and scientists likewise found other circumstantial proof that might hint that some sperm whales hunt Greenland sharks.