Northern Sea Otters Stock Photos, Pictures, Images, Illustrations

 
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Northern Sea Otters, Enhydra lutris kenyoni, Stock Photos, Pictures, Images and Illustrations

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Northern sea otters are a subspecies of sea otter, Enhydra lutris, found in the Aleutian Islands and the coasts of south mainland Alaska, British Columbia, and the U.S. State of Washington. This fact sheet will focus only on information related to this subspecies.

Northern sea otters share the basic physical characteristics of all Enhydra lutris sea otters, though they are said to be intermediate in size when compared to the larger Asian sea otter, Enhydra lutris lutris and the smaller southern sea otter, Enhydra lutris nereis. They are also said to have longer mandible bones than the other two subspecies. Northern sea otters are more likely to haul out on land and are more agile on land than both Southern sea otters and Asian sea otters (Davis, Lidicker, 1975).

After sea otters were nearly killed off by the fur trade in the 1700-1800s, they were finally protected by international treaty in 1911. Protection permitted populations to grow at a rate of 9% annually, and in some areas of the Aleutians, numbers approached pre-exploitation levels. By the 1980s, northern sea otters had reached all major Alaskan islands that they formerly inhabited.

Recovery of the Kenyoni subspecies was further aided by translocation efforts in the late 1960s. Northern sea otters from Amchitka and Prince William Sound were released in Oregon, Washington, and British Columbia, and stable populations were established everywhere except Oregon. Failure to recover in Oregon is assumed to be a result of an inadequate food supply. Populations in Washington are increasing at a rate of 8.2% per year and are on track to reach capacity (Jameson, 2005).

 

Northern Sea Otter Picture
Picture of northern sea otter or Alaskan sea otter, Enhydra lutris kenyoni, mother and pup, Prince William Sound, Alaska, North Pacific Ocean Image #: 010954

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Mammalia

Order: Carnivora

Suborder: Caniformia/Canoidea

Family: Mustelidae/Mustelids

Subfamily: Lutrinae

Genus: Enhydra

Specific: lutris

Species: Enhydra lutris

Subspecies: Enhydra lutris kenyoni

>>> More Northern Sea Otter Pictures

 

Thanks to natural recovery and translocation efforts, northern sea otters were expected to increase further in population throughout their historical range. Unfortunately, surveys in the 1990s discovered an unexpected and abrupt decline in Northern sea otter numbers in the Aleutian Islands. A survey in 2000 showed that Northern sea otters had declined by 70% from 1992 to 2000. In terms of number, that represents a catastrophic loss of 47,000 to 86,000 northern sea otters in the Aleutian Islands alone (Burn, Doroff, Tinker, 2003). Year 2000 population estimates in the Aleutians were less than 9,000 individuals remaining (Doroff, Estes, Tinker, Burn, Evans, 2003).

The reasons for this sudden drop-off in numbers in the Aleutian Islands are not entirely known. One reason put forth was increased predation by orcas (killer whales), which was probably due to an abrupt decline in numbers of the orca's preferred prey, harbor seals (Doroff, Estes, Tinker, Burn, Evans, 2003). The sudden drop in both pinnipeds and northern sea otters is a cause for concern, and provides evidence that sea otter populations must be protected and monitored wherever they occur.

Sea otters are listed as Threatened in Canada. Northern sea otters occupy small areas of the British Columbia coast and are said to be increasing in number there, with recent estimates at around 900 sea otters from an initial translocation of 89 individuals from Alaska in 1969 and 1972. Oil spills, environmental contamination, disease or fishing conflicts could adversely impact any of these populations, so they are by no means secure.

Sea otters in the State of Washington are listed as Endangered, though this designation will likely be downgraded to Threatened when sea otters reach a count of 1,640 individuals or more for 3 consecutive years. The most recent counts have been about half that. This number may seem small, but they are the offspring of only 59 sea otters that were reintroduced to Washington in 1969 and 1970. Like the British Columbia populations, they could be severely impacted by oil spills or other environmental disasters.

The number of sea otters in Alaska may be as high as 150,000. They continue to decrease in the Aleutians, but are increasing along the south mainland coast and the panhandle bordering British Columbia. The Aleutian population, called the Southwest Alaska stock of sea otters, is considered Threatened. The other stocks, called the South Central Stock and the Southeast Stock, are considered stable and are not designated as Threatened.

All sea otters now in existence are descendants of a fairly small number of exploitation era survivors. Consequently, there is little genetic diversity among sea otter populations, making them particularly vulnerable to disease or sudden environmental change.

Alternate names: Northern Sea Otter, Alaskan Sea Otter, Alaska Sea Otter

Links to SeaPics.com fact sheets on the other two subspecies of sea otter:

Asian sea otter (Enhydra lutris lutris) of Japan and Russia

Southern sea otter (Enhydra lutris nereis) of California

© Northern sea otter information assembled from on-line sources by Kevin Miller on June 4, 2008 for Seapics.com.

http://www-comm.pac.dfo-mpo.gc.ca/pages/consultations/sea-otters/recovery_e.htm

http://research.alaskasealife.org/otter_articles/Doroff_etal2003-Sea_Otter_Population_Declines_In_the_Aleutian_Archipelago.pdf

http://research.alaskasealife.org/otter_articles/Bodkin_etal2003-Sea_otter_pop_structure.pdf

http://research.alaskasealife.org/otter_articles/Davis_etal1975-Taxonomic_status.pdf

http://wdfw.wa.gov/wlm/research/papers/seaotter/survey/index.htm

http://wdfw.wa.gov/wlm/diversty/soc/recovery/seaotter/index.htm

http://www.adfg.state.ak.us/special/esa/non-endangered.php