Animal Diversity Web

Ge­o­graphic Range

Som­nio­sus mi­cro­cephalus is found in the north At­lantic, from the coast of New Eng­land and Canada to Scan­di­na­vian wa­ters. They oc­ca­sion­ally ven­ture as far south as the mouth of the Seine River in France. (Com­pagno and Fowler, 2005; Com­pagno, 1984; Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Biogeographic Regions
• atlantic ocean
  • native

Habi­tat

Som­nio­sus mi­cro­cephalus live mainly on con­ti­nen­tal and in­su­lar shelves. They oc­cupy in­ter­tidal re­gions in ad­di­tion to some river mouths and shal­low bay areas dur­ing the win­ter months and often move to depths from 180 to 550 me­ters dur­ing warmer months. They have been ob­served as low as 1200 me­ters, with one ob­ser­va­tion at 2200 me­ters off the coast of Geor­gia - ex­tend­ing its range both ge­o­graph­i­cally and in terms of depth. In north­ern parts of their range, Green­land sharks are found from 0 to 1200 me­ters in wa­ters from 1 to 12 de­grees Cel­sius. In south­ern parts of their range, these sharks may occur at greater depths. (Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Habitat Regions
• temperate
• polar
• saltwater or marine

• Aquatic Biomes
• pelagic
• coastal

• Other Habitat Features
• estuarine
• intertidal or littoral

• Range depth

  145 to 1200 m

  475.72 to 3937.01 ft

• Average depth

  180-550 m

  ft

Phys­i­cal De­scrip­tion

Som­nio­sus mi­cro­cephalus is a large, slug­gish shark that av­er­ages be­tween 2 and 4 me­ters in length. Most of the body is a medium grey or brown in color and some­times ex­hibits dark trans­verse bands or small spots or blotches that are lighter or darker than the base color. The snout is short and rounded, and the body is heavy and cylin­dri­cal in shape with small pre­cau­dal fins. No spines are pre­sent in the two equally-sized dor­sal fins, and the ven­tral lobe of the cau­dal fin is slightly elon­gated. No anal fin is pre­sent. The skin is quite rough, ex­hibit­ing den­ti­cles with curved pointed cusps. Teeth in the upper and lower jaws dif­fer in shape; upper teeth are spear-shaped while the lower teeth are shaped with high roots and low bent cusps for slic­ing. (Com­pagno and Fowler, 2005; Com­pagno, 1984; Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

• Range mass

  700 to 1000 kg

  1541.85 to 2202.64 lb

• Range length

  40 to 640 cm

  15.75 to 251.97 in

• Average length

  244 to 427 cm

  in

De­vel­op­ment

De­vel­op­ment in Som­nio­sus mi­cro­cephalus is ovo­vi­vip­a­rous; lit­ters of up to ten pups have been ob­served. Size of fully grown young at birth has not been con­firmed but is thought to be around forty cen­time­ters. Most adults grow to be­tween two and four me­ters in length. (Com­pagno, 1984)

Re­pro­duc­tion

Mat­ing by this species has never been ob­served, but fe­males have been found with mat­ing scars on their cau­dal fins. There­fore, it is in­ferred that, as is the case with most sharks, males bite fe­males until they sub­mit. Fer­til­iza­tion oc­curs in­ter­nally. ("Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group", 2005)

• Mating System
• polygynandrous (promiscuous)

Mat­ing has never been ob­served in this species and lit­tle in­for­ma­tion is avail­able con­cern­ing re­pro­duc­tion in Green­land sharks or re­lated species. ("Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group", 2005; Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Key Reproductive Features
• iteroparous
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• ovoviviparous

• Average number of offspring

  10

There is no spe­cific in­for­ma­tion on parental in­vest­ment in Green­land sharks. How­ever, most sharks are in­de­pen­dent im­me­di­ately after birth. Fe­males pro­vide de­vel­op­ing em­bryos with rich food sources to sup­port their de­vel­op­ment.

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female

Lifes­pan/Longevity

No spe­cific in­for­ma­tion about the longevity of Som­nio­sus mi­cro­cephalus ex­ists. Some sci­en­tists spec­u­late that these sharks may live in ex­cess of 100 years. ("Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group", 2005)

Be­hav­ior

Som­nio­sus mi­cro­cephalus is gen­er­ally de­scribed as a slug­gish. They spend much of their time hov­er­ing near the sea floor in search of food. They may also be ca­pa­ble of pur­su­ing prey. These sharks have been ob­served ex­hibit­ing the be­hav­ior of an­i­mals that often prey on seals, even stalk­ing a cam­era op­er­a­tor in one rare in­stance. How­ever, no at­tacks on hu­mans by this species have been con­firmed. Green­land sharks are soli­tary, out­side of the mat­ing sea­son or when large groups occur to ex­ploit car­rion, such as that pro­duced by the com­mer­cial fish­ing in­dus­try. ("Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group", 2005; Com­pagno and Fowler, 2005; Com­pagno, 1984; "Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group", 2005; Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Key Behaviors
• natatorial
• motile
• solitary

Com­mu­ni­ca­tion and Per­cep­tion

Like all sharks, Som­nio­sus mi­cro­cephalus has a lat­eral line which aids in the de­tec­tion of move­ment in the sur­round­ing wa­ters. Sharks also have es­pe­cially keen chem­i­cal per­cep­tion. No com­mu­ni­ca­tion has been ob­served within the species. ("Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group", 2005)

• Perception Channels
• tactile
• vibrations
• chemical
• electric

Food Habits

Fish, ma­rine mam­mals, and car­rion are three sta­ples in the diet of Som­nio­sus mi­cro­cephalus. Fish in­clude her­ring (Clu­peinae), salmon (Salmonidae), smelt (Os­meri­dae), cod (Ga­di­dae), pol­lock (Ther­a­gra), had­dock (Melanogram­mus), hal­ibut (Hip­poglos­sus), red­fish (Ho­plostethus), sculpins (Cot­toidei), lump­fish (Cy­clopterus), and skates (Ra­ji­formes). Seals (Pho­ci­dae) and small whales (Del­phinidae) are also com­mon food items. Drowned horses and rein­deer have also been found in the stom­achs of cap­tured spec­i­mens. Som­nio­sus mi­cro­cephalus has been ob­served feed­ing in great num­bers on car­rion pro­duced by com­mer­cial whal­ing and fish­ing op­er­a­tions. (Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Primary Diet
• carnivore
  • piscivore

• Animal Foods
• mammals
• fish
• carrion
• mollusks
• aquatic crustaceans
• echinoderms
• cnidarians

Pre­da­tion

There are no known preda­tors of adult Green­land sharks be­cause of their very large size. (Eagle, 2006)

Ecosys­tem Roles

Many of these sharks have cope­pod par­a­sites, Om­ma­tokoita elon­gata, at­tached to the corneas of their eyes. A sin­gle, fe­male cope­pod will at­tach it­self to one of the corneas, re­sult­ing in corneal dam­age and blind­ness in one eye. This does not seem to neg­a­tively ef­fect the shark, as they do not rely on their vi­sion. It has been sug­gested that the bi­o­lu­mi­nes­cence of these par­a­sites helps lure prey, thus re­sult­ing in a mu­tu­al­is­tic re­la­tion­ship, but there is no ev­i­dence to sup­port this. (Com­pagno and Fowler, 2005; Com­pagno, 1984)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Som­nio­sus mi­cro­cephalus is com­monly fished by peo­ple in the Arc­tic re­gions (Nor­way, Ice­land, and Green­land) for its liver oil and meat. Peo­ple of the Inuit tribes have also been known to use its skin to make boots and its teeth as knives. (Com­pagno and Fowler, 2005; Com­pagno, 1984)

• Positive Impacts
• food
• body parts are source of valuable material

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Un­less prop­erly washed or dried, Green­land shark meat is toxic to hu­mans. Like most sharks, Green­land sharks rarely at­tack un­less ha­rassed. (Com­pagno and Fowler, 2005; Com­pagno, 1984)

Con­ser­va­tion Sta­tus

The sta­tus of Green­land shark pop­u­la­tions are not well known. They sup­port a fish­ery for liver oil in Green­land, Nor­way, and Ice­land, but some re­searcher sus­pect that pop­u­la­tions have di­min­ished. They have an es­ti­mated pop­u­la­tion dou­bling time of 14 years. (Com­pagno and Fowler, 2005)

• IUCN Red List

  Near Threatened
  More information

• IUCN Red List

  Near Threatened
  More information

• US Federal List

  No special status

• CITES

  No special status

Other Com­ments

Green­land sharks are also known as sleeper sharks, ground sharks, gray sharks, and gurry sharks. They are known as ekalugssuak in Green­land, hakarl in Ice­land, and hak­jer­ring in Nor­way. (Eagle, 2006)

Con­trib­u­tors

Tanya Dewey (ed­i­tor), An­i­mal Di­ver­sity Web.

Patrick Mills (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Kevin Wehrly (ed­i­tor, in­struc­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

2005. "Green­land Shark and Elas­mo­branch Re­search and Ed­u­ca­tion Group" (On-line). Ac­cessed Oc­to­ber 18, 2005 at http://​www.​geerg.​ca.

Com­pagno, L. 1984. FAO Species Cat­a­logue Vol­ume 4:Sharks of the World. Rome: United Na­tions De­vel­op­ment Pro­gramme.

Com­pagno, L., S. Fowler. 2005. Sharks of the World. Prince­ton, New Jer­sey: Prince­ton Uni­ver­sity Press.

Eagle, D. 2006. "Bi­o­log­i­cal Pro­files: Green­land shark" (On-line). Florida Mu­seum of Nat­ural His­tory, Ichthy­ol­ogy De­part­ment. Ac­cessed Feb­ru­ary 10, 2006 at http://​www.​flmnh.​ufl.​edu/​fish/​Gallery/​Descript/​GreenlandShark/​GreenlandShark.​html.