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'Marine mammal'
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'[[File:Humpback Whale underwater shot.jpg|thumb|300px|right|A [[Humpback whale]] (''Megaptera novaeangliae''), a member of order [[Cetacea]]]] [[File:Hydrurga leptonyx edit1.jpg|thumb|300px|right| A [[Leopard seal]] (''Hydrurga leptonyx''), a member of suborder [[Pinniped]]ia of order [[Carnivora]]]] '''Marine mammals''', which include [[Pinniped|seal]]s, [[whale]]s, [[dolphin]]s, and [[walrus]]es, form a diverse group of 128 species that rely on the ocean for their existence.<ref name="pompa">Pompa, S., Ehrlich, P. R. & Ceballos, G. (2011) "Global distribution and conservation of marine mammals". PNAS 108 (33): 13600–13605 {{doi|10.1073/pnas.1101525108}}</ref> They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding.<ref name="jeff">Jefferson, T. A. , Webber, M. A. & Pitman, R. L. (2008) ''Marine Mammals of the World A Comprehensive Guide to their Identification'' London ; Burlington, MA: Academic ISBN 978-0-12-383853-7 7-16</ref> The level of dependence on the marine environment for existence varies considerably with species. For example, [[dolphin]]s and [[whale]]s are completely dependent on the marine environment for all stages of their life, whereas [[Pinniped|seal]]s feed in the ocean, but breed on land.<ref name=jeff/> Marine mammals can be subdivided into four recognised groups; [[cetaceans]] ([[whale]]s, [[dolphin]]s, [[porpoise]]s and [[narwhal]]), [[pinniped]]s ([[Pinniped|seal]]s, [[sea lion]]s and [[walrus]]es), [[sirenian]]s ([[manatee]]s and [[dugong]]s), and [[fissiped]]s, which are the group of carnivores with separate digits (the [[polar bear]], and two species of [[otter]]). Both [[cetaceans]] and [[sirenians]] are fully aquatic and therefore are obligate ocean dwellers. [[Pinniped]]s are semi-aquatic; they spend the majority of their time in the water, but need to return to land for important activities such as [[mating]], [[breeding in the wild|breeding]] and [[molting]]. In contrast, both [[otter]]s and the [[polar bear]] are much less adapted to ocean living.<ref name=jeff/> While the number of marine mammals is small compared to those found on land, their total [[biomass]] is large. They play important roles in maintaining [[marine ecosystem]]s, especially through regulation of prey populations.<ref name="kasc">Kaschner, K., Tittensor, D. P., Ready, J., Gerrodette, T. & Worm, B. (2011) "Current and Future Patterns of Global Marine Mammal Biodiversity" ''PLoS ONE'' 6(5): 19653 {{doi|10.1371/journal.pone.0019653}}</ref> These two factors make them an integral component of the marine environment. This is of particular concern considering 23% of marine mammal species are currently threatened.<ref name="ship">Shipper, J. , Chanson, J. S. & Chiozza, F. et al (2008) "The Status of the World’s Land and Marine Mammals: Diversity, Threat, and Knowledge" ''Science'' 322: 225-230 {{doi|10.1126/science.1165115}}</ref> ==Taxonomy== [[File:Ursus maritimus 4 1996-08-04.jpg|thumb|A [[Polar bear]] (''Ursus maritimus''), a member of family [[Ursidae]]]] [[File:Sea otter cropped.jpg|thumb|A [[Sea Otter]] (''Enhydra lutris''), a member of family [[Mustelidae]]]] Mammals have returned to the water in at least nine separate evolutionary [[lineage (evolution)|lineage]]s ([[Cetacea]], [[Sirenia]], [[Desmostylia]], [[Pinnipedia]], ''Ursus maritimus'' ([[polar bear]]), [[Kolponomos]] (marine bear), [[Thalassocnus]] (aquatic sloth), ''Enhydra lutris'' ([[sea otter]]) and ''Lontra feline'' ([[marine otter]])). Three of these lineages are extinct ([[Desmostylia]]; [[Kolponomos]]; [[Thalassocnus]]).<ref name=pompa/> Despite the diversity in morphology seen between groups, improving foraging efficiency has been the main driver in the [[evolution]] in these lineages.<ref>Uhen, M. D. (2007) "Evolution of Marine Mammals: Back to the Sea After 300 Million Years". ''The Anatomical Record''. 290:514-522 {{doi|10.1002/ar.20545}}</ref> Today, marine mammals belong to one of three orders; [[Cetacea]], [[Sirenia]], or [[Carnivora]]. Within the [[Order (biology)|Order]] [[Carnivora]] are the [[pinniped]]s ([[sealion]]s, [[walrus]]es and [[Pinniped|seal]]s), the [[polar bear]] (''Ursus maritimus''), and two [[otter]]s (''Endydra lutris'' and ''Lontra feline''.<ref name=jeff/> *Order Cetacea **Suborder [[Mysticeti]] (baleen whales) ***Family [[Balaenidae]] (right and bowhead whales) = 2 genera; four species ***Family Neobalaenidae ([[pygmy right whale]]) = one species ***Family Balaenopteridae ([[rorqual]]s) = 2 genera; 8 species ***Family [[Eschrichtiidae]] ([[gray whale]]) = 1 species **Suborder Odontoceti ([[toothed whale]]s) ***Family [[Physeteridae]] ([[sperm whale]]) = 1 species ***Family [[Kogiidae]] (pygmy and dwarf sperm whales = 1 genera; 2 species ***Family [[Monodontidae]] (narwhal and beluga) = two genera; two species ***Family Ziphiidae ([[beaked whale]]s) = 6 genera; 21 species ***Family [[Delphinidae]] ([[oceanic dolphin]]s) = 17 genera; 36 species ***Family Phocoenidae ([[porpoise]]s) = 2 genera; 6 species ***Family [[Platanistidae]] (South Asia river dolphin) = 1 species ***Family [[Iniidae]] (boto) 1 species ***Family [[Lipotidae]] (Baji) probably extinct ***Family [[Pontoporiidae]] (franciscana) = 1 species *Order [[Sirenia]] (sea cows) ***Family Trichechidae ([[manatee]]s) = 1 genus; 3 species ***Family [[Dugongidae]] ([[dugong]]s) = 1 species *Order [[Carnivora]] ([[carnivore]]s): ***Family [[Mustelidae]] ([[otter]]s) ''Enhydra lutris'' ([[sea otter]]) ''Lontra feline'' ([[marine otter]]) ***Family Ursidae ([[bear]]s) ''Ursus maritimus'' ([[polar bear]]) **Suborder [[Pinniped]]ia (sealions, walruses, seals) ***Family [[Eared seal|Otariidae]] ([[fur seal]]s and [[sea lion]]s) = 7 genera; 16 species ***Family [[Odobenidae]] ([[walrus]]) = 1 species ***Family [[Earless seal|Phocidae]] (true seals) = 13 genera; 18 species ==Diversity, distribution and habitat== Marine mammals are widely distributed throughout the globe, but their distribution is patchy and coincides with the productivity of the oceans.<ref name="berta">Berta, A & Sumich, J. L. (1999) ''Marine mammals: evolutionary biology''. San Diego: Academic Press ISBN 0-12-093225-3</ref> Species richness peaks at around 40° latitude, both north and south. This corresponds to the highest levels of [[primary production]] around North and South [[Americas|America]], [[Africa]], [[Asia]] and [[Australia]]. Total species range is highly variable for marine mammal species. On average most marine mammals have ranges which are equivalent or smaller than one-fifth of the [[Indian Ocean]].<ref name="ship"/> The variation observed in range size is a result of the different ecological requirements of each species and their ability to cope with a broad range of environmental conditions. There is a high degree of overlap between marine mammal species richness and areas of [[human impact on the environment]] which is of concern.<ref name=kasc/> ==Anatomy and physiology== [[File:Oceanic whale pump - journal.pone.0013255.g001.tiff|thumb|300px|right|Illustration of the oceanic whale pump that moves nutrients through the water column]] Marine mammals have a number of [[physiological]] and [[anatomical]] features to overcome the unique challenges associated with aquatic living. Some of these features are very species specific. Marine mammals have developed a number of features for efficient [[Animal locomotion|locomotion]] such as torpedo shaped bodies to reduce drag; modified limbs for [[Animal locomotion|propulsion]] and [[steering]]; tail flukes and [[dorsal fin]]s for propulsion and balance.<ref name=berta/> Marine mammals are adept at [[thermoregulation]] using dense [[fur]] or [[blubber]] to reduce heat loss; as well as circulatory adjustments to conserve their body temperature ([[counter-current heat exchange]]rs); torpedo shaped bodies, reduced appendages, and large size to prevent heat loss.<ref name=berta/> Most marine mammals are [[hypoosmotic]] and as a result they are constantly losing water to the surrounding environment. They have evolved a number of mechanisms to overcome this, but most retain their water by using highly efficient [[kidney]]s, that can concentrate urine.<ref name=berta/> Marine mammals are able to dive for long periods of time. Both [[pinniped]]s and [[cetacean]]s have large and complex [[blood vessel]] systems which serve to store [[oxygen]] to support deep diving. Other important reservoirs include [[muscle]]s, [[blood]], and the [[spleen]] which all have the capacity to hold a high concentration of oxygen. Other features include [[bradycardia]] (reduced heart rate), and [[vasoconstriction]] (shunts most of the oxygen to vital organs such as the brain and heart) also assist with extended diving and oxygen deprivation.<ref name=berta/> Sound travels differently through water therefore marine mammals have developed a number of ways to ensure effective [[communication]], [[prey]] capture, and [[predator]] detection.<ref name=white/> The most notable adaptation is the development of [[Animal echolocation|echolocation]] in [[whale]]s and [[dolphin]]s.<ref name=berta/> Lastly, Marine mammals have evolved a number features for feeding, which are mainly seen in their [[dentition]]. For example, the cheek teeth of [[pinniped]] and [[odontocetes]] are designed specifically to capture [[fish]] and [[squid]]. In contrast, Mysticetes have evolved [[baleen plate]]s to filter feed [[plankton]] and small fish from the water.<ref name=berta/> {{clear}} ==Threats== [[File:FL fig04.jpg|thumb|A [[West Indian Manatee]] (''Trichechus manatus''), a member of order [[Sirenia]]]] [[File:Sea lion family.JPG|right|thumb|[[California sea lion]]s, members of the family [[Otariidae]].]] [[File:Desmostylus2DB.jpg|right|thumb|''[[Desmostylus]]'' (extinct)]] ===Exploitation=== Marine mammals were hunted by coastal aboriginal humans historically for food and other resources. The effects of this were only localised, as hunting efforts were on a relatively small scale.<ref name=berta/> Later, commercial [[hunting]] was developed and marine mammals were heavily exploited. This led to the extinction of the [[Steller's Sea Cow]] and the [[Caribbean monk seal]].<ref name=berta/> Today, [[population]]s of species that were historically hunted, such as [[blue whale]]s ''Balaenoptera musculus'' and ''B. m. brevicauda''), and the [[North Pacific right whale]] (''Eubalaena japonica''), are much lower compared to their pre-exploited levels.<ref name="clap">Clapham, P. J., Young, S. B. & Brownel Jr, R. L. (1999) "Baleen whales: conservation issues and the status of the most endangered populations" ''Mammal Rev.'' 29(1): 35–60. {{doi|10.1046/j.1365-2907.1999.00035.x}}</ref> Because whales generally have slow growth rates, are slow to reach [[sexual maturity]], and have a low reproductive output, population recovery has been very slow.<ref name="white">Whitehead, H., Reeves, R. R. & Tyack, P. L. (1999) Science and the conversation,protection,and management of wild cetaceans (eds) J. Mann , R. C. Connor, P.L Tyack & H Whitehead in ''Cetacean societies : field studies of dolphins and whales''. Chicago : University of Chicago Press ISBN 226503402</ref> Despite the fact commercial whaling is generally a thing of the past since the passage of the [[International Whaling Commission]]’s (IWC) moratorium on commercial whaling, a number of marine mammals are still subject to direct hunting. The only remaining commercial hunting of whales is by [[Norway]] where several hundred northeastern North Atlantic minke whales are harvested each year. [[Japan]] also harvests several hundred Antarctic and North Pacific minke whales each year under the guise of scientific research.<ref name=clap/> However, the illegal trade of whale and dolphin meat is a significant market in some countries.<ref>Baker, C. S., Cipriano, F. & Palumbi, S. R (1996) "Molecular genetic identification of whale and dolphin products from commercial markets in Korea and Japan" ''Molecular Ecology'' 5: 671-685</ref> Seals and sealions [[seal hunting|are also still hunted]] in some areas such as Canada. ===By-catch and other incidental effects=== ====Entanglements==== [[By-catch]] is the incidental capture of non-target species in [[fisheries]]. Fixed and drift [[gill net]]s cause the highest [[Mortality rate|mortality]] levels for both [[cetacean]]s and [[pinniped]]s, however, entanglements in both trap and pot lines are also common, long lines, and mid-water trawls.<ref>W. F. Perrin 1994 Status of species (eds) Randall R. Reeves and Stephen Leatherwood in ''Dolphins, porpoises, and whales: 1994-1998 action plan for the conservation''. Gland, Switzerland: International Union for Conservation of Nature and Natural Resources</ref> [[Tuna]] [[Seine fishing|seines]] are particularly problematic for entanglement by dolphins.<ref>Hall, M. A. (1998) "An ecological view of the tuna dolphin problem: impacts and trade-offs" ''Reviews in Fish Biology and Fisheries''. 8: 1-34 {{doi|10.1023/A:1008854816580}}</ref> By-catch affects all cetaceans, both small and big, in all habitat types. However, smaller [[cetacean]]s and [[pinniped]]s are most vulnerable as their size means that escape once they are entangled is highly unlikely and they frequently drown.<ref name=clap/> While larger cetaceans are capable of dragging nets with them, the nets sometimes remain tightly attached to the individual and can impede the animal from feeding sometimes leading to [[starvation]].<ref name=clap/> Abandoned or lost nets and lines cause mortality through [[ingestion]] or entanglement.<ref name="and">Anderson, P. K. (2001) "Marine Mammals in the Next One Hundred Years: Twilight for a Pleistocene Megafauna?" ''Journal or Mammalogy'' 82(3): 623-629 {{doi|10.1644/1545-1542}}</ref> Marine mammals also get entangled in [[aquaculture]] nets, however, these are rare events and not prevalent enough to impact populations.<ref name="wur">Wursig, Bernd and Gailey, Glenn A. Marine Mammals and Aquaculture: Conflicts and Potential Resolutions (eds) Robert R Stickney and James P. McVey in ''Responsible marine aquaculture''. Wallingford, Oxon ; New York : CABI ISBN 0-85199-604-3</ref> ====Vessel Strikes and activity==== Vessel strikes cause death for a number of marine mammals, especially [[whale]]s.<ref name=clap/> In particular, fast commercial vessels such as [[container ship]]s can cause major injuries or death when they collide with marine mammals. Collisions occur both with large commercial vessels and [[recreational boat]]s and cause injury to whales or smaller cetaceans. The critically endangered [[northern right whale]]{{Disambiguation needed|date=February 2012}} is particularly affected by vessel strikes. [[Tourism]] boats designed for whale and [[dolphin watching]] can also negatively impact on marine mammals by interfering with their natural behavior.<ref name="const">Constantine, R., Brunton, D. H. & Dennis, T. (2004) "Dolphin-watching tour boats change bottlenose dolphin (Tursiops truncatus) behavior" ''Biological Conservation'' 117: 299-307 doi: 10. 10. 1016/j.biocon. 2003.12.009</ref> ===Habitat loss and degradation=== [[Habitat degradation]] is caused by a number of human activities. Marine mammals that live in coastal environments are most likely to be affected by habitat degradation and loss. Developments such as sewage [[marine outfall]]s, [[mooring (oceanography)|mooring]]s, [[dredging]], blasting, dumping, [[port]] construction, [[hydroelectric]] projects, and [[aquaculture]] both degrade the environment and take up valuable habitat.<ref name=white/> For example, extensive shellfish aquaculture takes up valuable space used by coastal marine mammals for important activities such as breeding, foraging and resting.<ref name=wur/> ===Competition/conflict with fisheries=== The fishery industry not only threatens marine mammals through by-catch, but also through competition for food. Large scale fisheries have led to the depletion of [[fish stock]]s that are important prey species for marine mammals. [[Pinniped]]s have been especially affected by the direct loss of food supplies and in some cases the harvesting of fish has led to food shortages or dietary deficiencies,<ref>Rosen, D. A. S. & Trites, A. W. (2000). "Pollock and the decline of Steller sea lions: testing the junk-food hypothesis" ''Canadian Journal of Zoology'' 78:1243- 1250 {{doi|10.1139/z00-060}}</ref> starvation of young, and reduced recruitment into the population.<ref>McAlpine, D. F., Stevick, P. T. & Murison, L. D. (1999). "Increase in extralimital occurrences of ice-breeding seals in the northern Gulf of Maine region: more seals or fewer fish?" ''Marine Mammal Science'' 15:906-911.</ref> As the fish stocks have been depleted, the [[competition]] between marine mammals and fisheries has sometimes led to conflict. Large-scale [[cull]]ing of populations of marine mammals by commercial fishers has been initiated in a number of areas in order to protect fish stocks for human consumption.<ref>Hutchins, J. (1996) "Spatial and temporal variation in the density of northern cod and a review of hypoth-eses for the stock's collapse". ''Canadian Journal of Fisheries and Aquatic Science'' 53:943-962.</ref> ===Competition/Conflict with Aquaculture=== Shellfish aquaculture takes up space so in effect creates competition for space. However, there is little direct competition for aquaculture shellfish [[harvest]].<ref name=wur/> On the other hand, marine mammals regularly take [[finfish]] from farms, which creates significant problems for marine farmers. While there are usually legal mechanisms designed to deter marine mammals, such as anti-predator nets or harassment devices, individuals are often illegally shot.<ref name=wur/> ===Pollution=== [[Contaminant]]s that are [[Effluent|discharged]] into the marine environment accumulate in the bodies of marine mammals when they are stored unintentionally in their [[blubber]] along with energy.<ref name=white/> Contaminants that are found in the tissues of marine mammals include [[heavy metals]] such as [[mercury (element)|mercury]] and [[lead]]; [[organochloride]]s; and [[polycyclic aromatic hydrocarbon]]s.<ref name=white/> For example, These can cause disruptive effects on [[endocrine system]]s;<ref name=and/> impair the reproductive system, and lower the immune system of individuals, leading to a higher number of deaths.<ref name=white/> Other pollutants such as [[Crude oil|oil]], [[plastic debris]] and [[sewage]] threaten the livelihood of marine mammals.<ref>Baker, J., Jones, A. M., Jones, T. P. & Watson H. C. (1981) "Otter Lutra lutra L Mortality and Marine Oil Pollution" ''Biological Conservation'' 20 311-321</ref> [[Noise pollution]] from anthropogenic activities is another major concern for marine mammals. This is a problem because underwater noise pollution interferes with the abilities of some marine mammals to communicate, and locate both predators and prey.<ref>Harwood, J. (2001) "Marine Mammals and their Environment in the Twenty-First Century" . ''Journal of Mammalogy''. 82(3): 630-640. http://www.jstor.org/stable/1383602</ref> [[Underwater explosion]]s are used for a variety of purposes including [[military]] activities, construction and [[oceanographic]] or [[geophysical]] research. They can cause injuries such as hemorrhaging of the lungs, and contusion and ulceration of the [[gastrointestinal tract]].<ref name=clap/> Underwater noise is generated from [[shipping]], the oil and gas industry, [[research]], and military use of [[sonar]] and oceanographic acoustic experimentation. Acoustic harassment devices and acoustic deterrent devices used by [[aquaculture]] facilities to scare away marine mammals emit loud and noxious underwater sounds.<ref name=wur/> ===Global Climate Change=== Two changes to the global [[atmosphere]] due to [[anthropogenic activity]] threaten marine mammals. The first is increases in [[ultraviolet radiation]] due to [[ozone depletion]], and this mainly affects the [[Antarctic]] and other areas of the [[southern hemisphere]].<ref name=white/> An increase in ultraviolet radiation has the capacity to decrease [[phytoplankton]] abundance, which forms the basis of the [[food chain]] in the ocean.<ref>McKenzie, R. L., Björn, L. O., Bais, A. & Ilyasd, M (2003) "Changes in biologically active ultraviolet radiation reaching the Earth’s surface" ''Photochem. Photobiol. Sci.'' 2: 5–15. {{doi|10.1016/S1011-1344(98)00182-1}}</ref> The second effect of [[global climate change]] is [[global warming]] due to increased [[carbon dioxide]] levels in the atmosphere. Raised sea levels, sea temperature and changed currents are expected to affect marine mammals by altering the distribution of important prey species, and changing the suitability of breeding sites and migratory routes.<ref>Simmonds, M. P. & Isaac, S. J. (2007) "The impacts of climate change on marine mammals: early signs of significant problems" ''Oryx'' 41(1): 19-26 {{doi|10.1017/S0030605307001524}}</ref> ==See also== * [[Aquatic mammal]] * [[Aquatic animal]] * [[Marine mammals as food]] * [[U.S. Navy Marine Mammal Program]] ==References== {{reflist|1}} ==External links== "http://www.ucmp.berkeley.edu/mammal/mesaxonia/desmostylia.html"http://www.ucmp.berkeley.edu/mammal/mesaxonia/desmostylia.html [[Category:Marine mammals]] {{Link GA|de}}'
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'YAY SHARKS these be sharks and stuff so like yeah have fun.'
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1362163822