Editing Marine mammal (section)

==Distribution and habitat==
[[File:Predicted patterns of marine mammal species richness.png|thumb|Marine mammal species richness: A) All species (n = 115), B) [[toothed whale]]s (n = 69), C) [[baleen whale]]s (n = 14), D) [[Pinniped|seals]] (n = 32), based on data from 1990 to 1999<ref>{{cite journal|last1=Kaschner|first1=K.|last2=Tittensor|first2=D. P.|last3=Ready|first3=J.|last4=Gerrodette|first4=T.|last5=Worm|first5=B.|year=2011|title=Current and future patterns of global marine mammal biodiversity|journal=PLOS ONE|volume=6|issue=5|page=e19653|doi=10.1371/journal.pone.0019653|bibcode=2011PLoSO...619653K|pmid=21625431|pmc=3100303|doi-access=free}}</ref>]]

Marine mammals are widely distributed throughout the globe, but their distribution is patchy and coincides with the productivity of the oceans.<ref name="berta">{{cite book|last1=Berta|first1=A|last2=Sumich|first2=J. L.|year= 1999|title=Marine Mammals: Evolutionary Biology|chapter=Exploitation and conservation|location=San Diego|publisher=Academic Press|isbn=978-0-12-093225-2|oclc=42467530}}</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. The high degree of overlap between marine mammal species richness and areas of [[human impact on the environment]] is of concern.<ref name=kasc/>

Most marine mammals, such as seals and sea otters, inhabit the coast. Seals, however, also use a number of terrestrial habitats, both continental and island. In temperate and tropical areas, they [[hauling-out|haul-out]] on to sandy and [[pebble]] beaches, [[rocky shore]]s, [[shoal]]s, [[mud flat]]s, [[tide pool]]s and in [[sea cave]]s. Some species also rest on man-made structures, like [[pier]]s, [[jetties]], [[buoy]]s and [[oil platform]]s. Seals may move further inland and rest in sand dunes or vegetation, and may even climb cliffs.<ref name=thepinnipeds>{{cite book|last=Riedman, M.|year=1990|title=The Pinnipeds: Seals, Sea Lions, and Walruses|url=https://archive.org/details/pinnipedssealsse0000ried_s7p5|url-access=registration|publisher=University of California Press|location=Los Angeles|isbn=978-0-520-06497-3|oclc=19511610}}</ref>{{rp|96}} Most cetaceans live in the open ocean, and species like the [[sperm whale]] may dive to depths of {{convert|-1000|to|-2500|ft}} in search of food.<ref>{{cite book|ref=Whitehead|title=Sperm Whales: Social Evolution in the Ocean|last=Whitehead, H.|year=2003|page=[https://archive.org/details/spermwhalessocia0000whit/page/79 79]|isbn=978-0-226-89518-5|oclc=51242162|publisher=University of Chicago Press|location=Chicago|url=https://archive.org/details/spermwhalessocia0000whit/page/79}}</ref> Sirenians live in shallow coastal waters, usually living {{convert|30|ft|m}} below sea level. However, they have been known to dive to {{convert|-120|ft}} to forage deep-water [[seagrass]]es.<ref>{{cite book|last1=Marsh|first1=H.|last2=Eros|first2= Carole|last3=Hugues|first3=Joanna|last4=Penrose|first4=Helen|year=2002|url=https://portals.iucn.org/library/sites/library/files/documents/2002-001.pdf|title=Dugong: status reports and action plans for countries and territories| publisher=International Union for Conservation of Nature|isbn=978-92-807-2130-0|oclc=51040880}}</ref> Sea otters live in protected areas, such as rocky shores, [[kelp forest]]s, and [[Coral reef|barrier reefs]],<ref>{{cite book|last1=Silverstein|first1=Alvin|last2=Silverstein|first2=Virginia|last3=Silverstein|first3=Robert|year=1995|title=The Sea Otter|url=https://archive.org/details/seaotterendanger00alvi|url-access=registration|location=Brookfield, Connecticut|publisher=The Millbrook Press, Inc.|isbn=978-1-56294-418-6|oclc= 30436543|page=[https://archive.org/details/seaotterendanger00alvi/page/19 19]}}</ref> although they may reside among [[drift ice]] or in sandy, muddy, or silty areas.<ref>{{cite book|last1=Kenyon|first1=Karl W.|year=1975|title=The Sea Otter in the Eastern Pacific Ocean|location= New York|publisher=Dover Publications|isbn=978-0-486-21346-0|oclc=1504461}}</ref>

Many marine mammals seasonally migrate. Annual ice contains areas of water that appear and disappear throughout the year as the weather changes, and seals migrate in response to these changes. In turn, polar bears must follow their prey. In [[Hudson Bay]], [[James Bay]], and some other areas, the ice melts completely each summer (an event often referred to as "ice-floe breakup"), forcing polar bears to go onto land and wait through the months until the next freeze-up. In the [[Chukchi Sea|Chukchi]] and [[Beaufort Sea|Beaufort]] seas, polar bears retreat each summer to the ice further north that remains frozen year-round.<ref name="distribution">{{cite book |last=Stirling |first=Ian |year=1988 |title=Polar Bears |location=Ann Arbor |publisher=University of Michigan Press |isbn=978-0-472-10100-9 |chapter=Distribution and Abundance |chapter-url=https://archive.org/details/polarbears00stir |url-access=registration |url=https://archive.org/details/polarbears00stir }}</ref> Seals may also migrate to other environmental changes, such as [[El Niño]], and traveling seals may use various features of their environment to reach their destination including geomagnetic fields, water and wind currents, the position of the sun and moon and the taste and temperature of the water.<ref name=thepinnipeds/>{{rp|256–257}} Baleen whales famously migrate very long distances into tropical waters to give birth and raise young,<ref>{{cite book|chapter-url={{Google books|plainurl=yes|id=wCE4AAAAIAAJ|page=111}} |editor-first=D.|editor-last=Aidley|first1=C. J. H.|last1= Lockyer|first2=S. G.|last2=Brown|year=1981|title=Animal Migration|chapter=The Migration of Whales|page=111|isbn=978-0-521-23274-6|publisher=CUP Archive}}</ref> possibly to prevent predation by killer whales.{{sfn|Perrin|2009|loc=[https://books.google.com/books?id=2rkHQpToi9sC&pg=PA360 p. 360]}} The [[gray whale]] has the longest recorded migration of any mammal, with one traveling {{convert|14000|mi}} from the [[Sea of Okhotsk]] to the [[Baja Peninsula]].<ref>{{cite magazine|url=http://news.nationalgeographic.com/2015/04/150414-gray-whale-pacific-migration-endangered-ocean-animal-science/|archive-url=https://web.archive.org/web/20150416092324/http://news.nationalgeographic.com/2015/04/150414-gray-whale-pacific-migration-endangered-ocean-animal-science/|url-status=dead|archive-date=April 16, 2015|first=Jane J.|last=Lee|year=2015|title=A Gray Whale Breaks The Record For Longest Mammal Migration|magazine=National Geographic|access-date=23 January 2016}}</ref> During the winter, manatees living at the northern end of their range migrate to warmer waters.<ref>{{Cite iucn | author = Deutsch, C.J. | author2 = Self-Sullivan, C. | author3 = Mignucci-Giannoni, A. | name-list-style = amp | title = ''Trichechus manatus'' | volume = 2008 | page = e.T22103A9356917 | date = 2008 | doi = 10.2305/IUCN.UK.2008.RLTS.T22103A9356917.en }}</ref>