Lontra canadensis - (Schreber, 1777)
North American River Otter
Other English Common Names: North American Otter, North American river otter, Northern River Otter, River Otter
Synonym(s): Lutra canadensis (Schreber, 1777)
Taxonomic Status: Accepted
Related ITIS Name(s): Lontra canadensis (Schreber, 1777) (TSN 180549)
French Common Names: loutre de rivière
Unique Identifier: ELEMENT_GLOBAL.2.102243
Element Code: AMAJF10010
Informal Taxonomy: Animals, Vertebrates - Mammals - Carnivores
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Mammalia Carnivora Mustelidae Lontra
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: Jones, C., R. S. Hoffman, D. W. Rice, M. D. Engstrom, R. D. Bradley, D. J. Schmidly, C. A. Jones, and R. J. Baker. 1997. Revised checklist of North American mammals north of Mexico, 1997. Occasional Papers, Museum of Texas Tech University 173:1-20.
Concept Reference Code: B97JON01EHUS
Name Used in Concept Reference: Lontra canadensis
Taxonomic Comments: Formerly included in the genus Lutra. Van Zyll de Jong (1987) used the generic name Lontra for New World otters; this is appropriate if New World otters are more closely related to Aonyx otters of Africa than to Lutra otters of Eurasia and Africa. Jones et al. (1997) and Wozencraft (in Wilson and Reeder 1993, 2005) followed van Zyll de Jong in using Lontra as the generic name. Rice (1998) retained this species in the genus Lutra. Bininda-Emonds et al. 1999) supported the separation of New World otters (except Pteronura) into Lontra.

Patterns of genetic variation do not concur with current subspecific designations (Serfass et al. (1998), and numerous translocations have crossed subspecies' range boundaries; hence the use of subspecific names is not meaningful in many cases.
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 04Apr2016
Global Status Last Changed: 18Nov1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Large range in much of North America north of Mexico; population trend probably is relatively stable; recent reintroduction and management efforts have improved conservation status.
Nation: United States
National Status: N5 (05Sep1996)
Nation: Canada
National Status: N5 (31Dec2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S4), Alaska (S5), Arizona (S1), Arkansas (S5), California (SNR), Colorado (S3S4), Connecticut (S5), Delaware (S4), District of Columbia (S1), Florida (SNR), Georgia (S5), Idaho (S4), Illinois (S2), Indiana (S3), Iowa (S3), Kansas (S3), Kentucky (S3S4), Louisiana (S4), Maine (S5), Maryland (S5), Massachusetts (S4), Michigan (S4), Minnesota (SNR), Mississippi (S4), Missouri (S5), Montana (S4), Navajo Nation (S1), Nebraska (S4), Nevada (S2), New Hampshire (S5), New Jersey (S4), New Mexico (SH), New York (S5), North Carolina (S4), North Dakota (S1), Ohio (S3), Oklahoma (S2), Oregon (S4), Pennsylvania (S4), Rhode Island (S4), South Carolina (SNR), South Dakota (S2), Tennessee (S3), Texas (S3), Utah (S3S4), Vermont (S5), Virginia (S4), Washington (S4), West Virginia (S4), Wisconsin (S4S5), Wyoming (S3)
Canada Alberta (S4), British Columbia (S5), Labrador (S5), Manitoba (S5), New Brunswick (S5), Newfoundland Island (S5), Northwest Territories (S4), Nova Scotia (S5), Nunavut (SU), Ontario (S5), Prince Edward Island (SX), Quebec (S5), Saskatchewan (S3S4), Yukon Territory (S4)

Other Statuses

IUCN Red List Category: LC - Least concern
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix II

NatureServe Global Conservation Status Factors

Range Extent: 20,000-2,500,000 square km (about 8000-1,000,000 square miles)
Range Extent Comments: Throughout most of North America north of Mexico, except the extreme southwestern U.S. Extirpated from large areas of the interior U.S. following European colonization. Has been reintroduced in some parts of the range (e.g., Colorado, Virginia).

Number of Occurrences: 81 to >300
Number of Occurrences Comments: The large range likely is divisible into at least 100 element occurrences.

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Total population size is unknown but may exceed 10,000 individuals.

Overall Threat Impact Comments: Local/regional declines were caused by unregulated trapping and degradation of riverine/riparian habitat. Oil contamination resulted in reduced habitat availability in Alaska (Bowyer et al. 1995).

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Population trend probably is relatively stable overall.

Other NatureServe Conservation Status Information

Protection Needs: Maintain productive aquatic habitats. Prevent excessive harvest. Support reintroduction and habitat restoration efforts.

Distribution
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Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Throughout most of North America north of Mexico, except the extreme southwestern U.S. Extirpated from large areas of the interior U.S. following European colonization. Has been reintroduced in some parts of the range (e.g., Colorado, Virginia).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, AL, AR, AZ, CA, CO, CT, DC, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NN, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, LB, MB, NB, NF, NS, NT, NU, ON, PEextirpated, QC, SK, YT

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: Sechrest, 2002


U.S. Distribution by County Help
State County Name (FIPS Code)
AK Kodiak Island (02150)
CA San Bernardino (06071)*
IA Allamakee (19005), Boone (19015)*, Clayton (19043), Clinton (19045)*, Dubuque (19061), Jackson (19097), Scott (19163)
IL Adams (17001), Alexander (17003), Bond (17005), Boone (17007), Bureau (17011), Calhoun (17013), Carroll (17015), Cass (17017), Clark (17023), Clinton (17027), Coles (17029), Cook (17031), Crawford (17033), Cumberland (17035), De Witt (17039), DeKalb (17037), Douglas (17041), DuPage (17043), Edwards (17047), Effingham (17049), Fayette (17051), Franklin (17055), Fulton (17057), Gallatin (17059), Hamilton (17065), Hancock (17067), Henderson (17071), Henry (17073), Jackson (17077), Jasper (17079), Jefferson (17081), Jersey (17083), Jo Daviess (17085), Johnson (17087), Kane (17089)*, Kendall (17093)*, Knox (17095), La Salle (17099), Lake (17097), Lee (17103), Macoupin (17117), Marion (17121), Marshall (17123), Mason (17125), Massac (17127), Mcdonough (17109), Mchenry (17111), Mclean (17113), Menard (17129), Mercer (17131), Monroe (17133), Montgomery (17135), Morgan (17137), Moultrie (17139), Ogle (17141), Peoria (17143), Perry (17145), Pike (17149), Pope (17151), Pulaski (17153), Putnam (17155), Randolph (17157), Rock Island (17161), Saline (17165), Sangamon (17167), Schuyler (17169), Shelby (17173), St. Clair (17163), Stephenson (17177), Tazewell (17179), Union (17181), Vermilion (17183), Wabash (17185), Warren (17187), Wayne (17191), White (17193), Whiteside (17195), Winnebago (17201)
IN Carroll (18015), Cass (18017), Clay (18021), Clinton (18023), Crawford (18025), Dubois (18037), Gibson (18051), Greene (18055), Hancock (18059), Harrison (18061), Hendricks (18063), Huntington (18069), Jackson (18071), Johnson (18081), Kosciusko (18085), Lagrange (18087), Lake (18089), Marion (18097), Monroe (18105), Montgomery (18107), Morgan (18109), Newton (18111), Noble (18113), Orange (18117), Pike (18125), Posey (18129), Pulaski (18131), Putnam (18133), Ripley (18137), Shelby (18145), St. Joseph (18141), Vigo (18167), Wabash (18169), Warrick (18173), White (18181)
MO Butler (29023)
NE Antelope (31003), Blaine (31009), Boone (31011), Boyd (31015), Brown (31017), Buffalo (31019), Burt (31021), Butler (31023), Cass (31025), Cherry (31031), Cuming (31039), Custer (31041), Dakota (31043), Dawson (31047), Deuel (31049), Dodge (31053), Douglas (31055), Furnas (31065)*, Gage (31067), Garden (31069), Garfield (31071), Greeley (31077), Hall (31079), Hamilton (31081), Harlan (31083), Holt (31089), Howard (31093), Jefferson (31095), Johnson (31097), Kearney (31099), Keith (31101), Knox (31107), Lincoln (31111), Loup (31115), Madison (31119), Merrick (31121), Morrill (31123), Nance (31125), Nemaha (31127), Otoe (31131), Phelps (31137), Platte (31141), Polk (31143), Rock (31149), Sarpy (31153), Saunders (31155), Scotts Bluff (31157), Sheridan (31161), Sherman (31163), Sioux (31165), Valley (31175), Wheeler (31183)
NM Grant (35017)*
NV Clark (32003)*
OK Atoka (40005), Canadian (40017), Craig (40035), Delaware (40041), Haskell (40061), Hughes (40063), Kingfisher (40073), Latimer (40077), Le Flore (40079), Logan (40083), McCurtain (40089), McIntosh (40091), Muskogee (40101), Okfuskee (40107), Oklahoma (40109), Pittsburg (40121), Pushmataha (40127), Rogers (40131), Tulsa (40143)
PA Bucks (42017), Lackawanna (42069), Luzerne (42079)*, Monroe (42089)*, Pike (42103)*, Wayne (42127), Wyoming (42131)
SD Beadle (46005), Bon Homme (46009), Brookings (46011), Brown (46013), Brule (46015), Buffalo (46017), Clay (46027), Codington (46029), Custer (46033), Day (46037), Deuel (46039), Grant (46051), Haakon (46055), Hamlin (46057), Hanson (46061), Hughes (46065), Hutchinson (46067), Jerauld (46073), Jones (46075), Lincoln (46083), Lyman (46085), Marshall (46091), McCook (46087), Meade (46093), Minnehaha (46099), Moody (46101), Pennington (46103), Roberts (46109), Sanborn (46111), Spink (46115), Stanley (46117), Sully (46119), Tripp (46123), Union (46127)
UT Box Elder (49003)*, Cache (49005), Carbon (49007)*, Daggett (49009), Duchesne (49013), Garfield (49017), Grand (49019), Juab (49023)*, Kane (49025), Millard (49027)*, Morgan (49029), Piute (49031)*, Rich (49033)*, Salt Lake (49035)*, San Juan (49037), Sanpete (49039)*, Sevier (49041)*, Summit (49043), Uintah (49047), Utah (49049)*, Wasatch (49051), Wayne (49055)*, Weber (49057)
WY Albany (56001), Big Horn (56003), Carbon (56007), Fremont (56013), Goshen (56015), Hot Springs (56017), Johnson (56019), Laramie (56021), Lincoln (56023), Natrona (56025), Park (56029), Sheridan (56033), Sublette (56035), Sweetwater (56037), Teton (56039), Uinta (56041), Washakie (56043)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
02 Lackawaxen (02040103)+, Middle Delaware-Mongaup-Brodhead (02040104)+*, Middle Delaware-Musconetcong (02040105)+, Lehigh (02040106)+, Upper Susquehanna-Tunkhannock (02050106)+, Upper Susquehanna-Lackawanna (02050107)+*
04 St. Joseph (04050001)+
05 Salamonie (05120102)+, Eel (05120104)+, Middle Wabash-Deer (05120105)+, Tippecanoe (05120106)+, Wildcat (05120107)+, Vermilion (05120109)+, Sugar (05120110)+, Middle Wabash-Busseron (05120111)+, Embarras (05120112)+, Lower Wabash (05120113)+, Little Wabash (05120114)+, Skillet (05120115)+, Upper White (05120201)+, Lower White (05120202)+, Eel (05120203)+, Driftwood (05120204)+, Muscatatuck (05120207)+, Lower East Fork White (05120208)+, Patoka (05120209)+, Blue-Sinking (05140104)+, Lower Ohio-Little Pigeon (05140201)+, Highland-Pigeon (05140202)+, Lower Ohio-Bay (05140203)+, Saline (05140204)+, Lower Ohio (05140206)+
07 Upper Minnesota (07020001)+, Coon-Yellow (07060001)+, Grant-Little Maquoketa (07060003)+, Apple-Plum (07060005)+, Maquoketa (07060006)+, Copperas-Duck (07080101)+, Lower Wapsipinicon (07080103)+*, Flint-Henderson (07080104)+, Pecatonica (07090003)+, Sugar (07090004)+, Lower Rock (07090005)+, Kishwaukee (07090006)+, Green (07090007)+, Middle Des Moines (07100004)+*, Bear-Wyaconda (07110001)+, The Sny (07110004)+, Kankakee (07120001)+, Chicago (07120003)+, Des Plaines (07120004)+, Upper Fox (07120006)+*, Lower Fox (07120007)+*, Lower Illinois-Senachwine Lake (07130001)+, Lower Illinois-Lake Chautauqua (07130003)+, Mackinaw (07130004)+, Spoon (07130005)+, South Fork Sangamon (07130007)+, Lower Sangamon (07130008)+, Salt (07130009)+, La Moine (07130010)+, Lower Illinois (07130011)+, Macoupin (07130012)+, Cahokia-Joachim (07140101)+, Upper Mississippi-Cape Girardeau (07140105)+, Big Muddy (07140106)+, Cache (07140108)+, Upper Kaskaskia (07140201)+, Middle Kaskaskia (07140202)+, Shoal (07140203)+, Lower Kaskaskia (07140204)+
09 Bois De Sioux (09020101)+, Western Wild Rice (09020105)+
10 Gallatin (10020008)+, Yellowstone Headwaters (10070001)+, Clarks Fork Yellowstone (10070006)+, Upper Wind (10080001)+, Little Wind (10080002)+, Popo Agie (10080003)+, Lower Wind (10080005)+, Upper Bighorn (10080007)+, Nowood (10080008)+, Greybull (10080009)+, Big Horn Lake (10080010)+, North Fork Shoshone (10080012)+, South Fork Shoshone (10080013)+, Shoshone (10080014)+, Middle Fork Powder (10090201)+, Clear (10090206)+, Middle Cheyenne-Spring (10120109)+, Middle Cheyenne-Elk (10120111)+, Lower Cheyenne (10120112)+, Lower Belle Fourche (10120202)+, Lower Lake Oahe (10130105)+, Fort Randall Reservoir (10140101)+, Bad (10140102)+, Medicine (10140104)+, Lower White (10140204)+, Ponca (10150001)+, Upper Niobrara (10150003)+, Middle Niobrara (10150004)+, Lower Niobrara (10150007)+, Upper James (10160003)+, Elm (10160004)+, Middle James (10160006)+, Lower James (10160011)+, Lewis and Clark Lake (10170101)+, Vermillion (10170102)+, Middle Big Sioux Coteau (10170201)+, Upper Big Sioux (10170202)+, Lower Big Sioux (10170203)+, Upper North Platte (10180002)+, Pathfinder-Seminoe Reservoirs (10180003)+, Medicine Bow (10180004)+, Sweetwater (10180006)+, Middle North Platte-Casper (10180007)+, Middle North Platte-Scotts Bluff (10180009)+, Upper Laramie (10180010)+, Horse (10180012)+, Lower North Platte (10180014)+, Cache La Poudre (10190007)+, Lone Tree-Owl (10190008)+, Crow (10190009)+, Lower Lodgepole (10190016)+, Middle Platte-Buffalo (10200101)+, Wood (10200102)+, Middle Platte-Prairie (10200103)+, Lower Platte-Shell (10200201)+, Lower Platte (10200202)+, Lower Middle Loup (10210003)+, South Loup (10210004)+, Lower North Loup (10210007)+, Calamus (10210008)+, Loup (10210009)+, Cedar (10210010)+, Upper Elkhorn (10220001)+, North Fork Elkhorn (10220002)+, Lower Elkhorn (10220003)+, Blackbird-Soldier (10230001)+, Big Papillion-Mosquito (10230006)+, Keg-Weeping Water (10240001)+, Tarkio-Wolf (10240005)+, Little Nemaha (10240006)+, Harlan County Reservoir (10250009)+, Lower Sappa (10250011)+*, Prairie Dog (10250015)+, Middle Republican (10250016)+, Lower Big Blue (10270205)+, Lower Little Blue (10270207)+
11 Current (11010008)+, Lower Cimarron-Skeleton (11050002)+, Lower Verdigris (11070105)+, Caney (11070106)+, Bird (11070107)+, Lower Neosho (11070209)+, Lower Canadian-Walnut (11090202)+, Little (11090203)+, Lower Canadian (11090204)+, Lower North Canadian (11100302)+, Deep Fork (11100303)+, Dirty-Greenleaf (11110102)+, Robert S. Kerr Reservoir (11110104)+, Poteau (11110105)+, Muddy Boggy (11140103)+, Kiamichi (11140105)+, Upper Little (11140107)+, Mountain Fork (11140108)+
14 Westwater Canyon (14030001)+, Lower Dolores (14030004)+, Upper Colorado-Kane Springs (14030005)+, Upper Green (14040101)+, New Fork (14040102)+, Upper Green-Slate (14040103)+, Big Sandy (14040104)+, Bitter (14040105)+, Upper Green-Flaming Gorge Reservoir (14040106)+, Blacks Fork (14040107)+, Little Snake (14050003)+, Lower White (14050007)+, Lower Green-Diamond (14060001)+, Ashley-Brush (14060002)+, Duchesne (14060003)+, Strawberry (14060004)+, Lower Green-Desolation Canyon (14060005)+, Price (14060007)+*, Lower Green (14060008)+, San Rafael (14060009)+*, Upper Lake Powell (14070001)+, Lower Lake Powell (14070006)+*, Lower San Juan (14080205)+
15 Lake Mead (15010005)+*, Havasu-Mohave Lakes (15030101)+*, Piute Wash (15030102)+*, Upper Gila-Mangas (15040002)+*
16 Upper Bear (16010101)+, Central Bear (16010102)+, Bear Lake (16010201)+*, Middle Bear (16010202)+, Little Bear-Logan (16010203)+, Lower Bear-Malad (16010204)+*, Upper Weber (16020101)+, Lower Weber (16020102)+, Utah Lake (16020201)+*, Spanish Fork (16020202)+*, Provo (16020203)+*, Jordan (16020204)+*, Northern Great Salt Lake Desert (16020308)+*, Upper Sevier (16030001)+*, East Fork Sevier (16030002)+*, Middle Sevier (16030003)+*, San Pitch (16030004)+*, Lower Sevier (16030005)+*, Sevier Lake (16030009)+*
17 Snake headwaters (17040101)+, Gros Ventre (17040102)+, Greys-Hobock (17040103)+, Palisades (17040104)+, Salt (17040105)+, Lower Henrys (17040203)+, Teton (17040204)+, Raft (17040210)+*, Goose (17040211)+*
19 Kodiak-Afognak Islands (19020701)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A large mustelid (otter).
Reproduction Comments: Implantation is delayed 8 months or more. Gestation, including delayed implantation, lasts 9-12 months. In many areas, births peak in late winter-early spring; parturition dates may not be closely synchronized within a given population. Litter size is 1-6 (average 2-3); 1 litter per year. Young may first enter water at about 7 weeks, are weaned at about 3 months, stay with mother for about a year. Male may rejoin family after young leave den. Females breed for the first time at 2 years. Males become sexually mature at 2 years, but may not breed successfully until 5-7 years old. Females evidently breed in alternate years in some areas (e.g., Alabama, Georgia), every year in Oregon (see Toweill and Tabor 1982).
Ecology Comments: Home range typically is linear; 20-30 miles for a pair or male; less for females with young (Jackson 1961). May hunt over as much as 80-100 km of stream during the course of one year. In coastal Alaska, summer home range size averaged around 20 km of shoreline in males, 10 km in females, with ranges twice as large in oiled areas (Bowyer et al. 1995).

Population density of one per 2.2 miles has been recorded (Baker 1983). Density was estimated at one otter per 86 ha of coastal marsh in Louisiana (Shirley et al. 1988). In Idaho, density was one family group and 1-3 subadults or nonbreeding adults per 15 km of waterway, plus one breeding adult male for each 20-30 km of waterway (see Toweill and Tabor 1982). Density in coastal areas of the Gulf of Alaska was 0.30-0.85 otters/km of shoreline (Testa et al. 1994, Bowyer et al. 1995).

Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Marine Habitat(s): Near shore
Estuarine Habitat(s): Forested wetland, Herbaceous wetland, Lagoon, River mouth/tidal river, Scrub-shrub wetland, Tidal flat/shore
Riverine Habitat(s): BIG RIVER, CREEK, Low gradient, MEDIUM RIVER, Moderate gradient, Pool
Lacustrine Habitat(s): Deep water, Shallow water
Palustrine Habitat(s): FORESTED WETLAND, HERBACEOUS WETLAND, Riparian, SCRUB-SHRUB WETLAND
Special Habitat Factors: Burrowing in or using soil, Fallen log/debris
Habitat Comments: Streams, lakes, ponds, swamps, marshes, estuaries (in some areas), beaver flowages, exposed outer coast (Pacific Northwest, Alaska). When inactive, occupies hollow log, space under roots, log, or overhang, abandoned beaver lodge, dense thicket near water, or burrow of other animal; such sites also are used for rearing young. Highly associated with beaver on Mount Desert Island, Maine (Dubuc et al. 1990). Uses traditional haul-out sites along the banks of aquatic habitats. May travel long distances overland, particularly in snow.
Adult Food Habits: Carnivore, Invertivore, Piscivore
Immature Food Habits: Carnivore, Invertivore, Piscivore
Food Comments: Feeds opportunistically on aquatic animals, particularly fishes (mostly slow-moving, mid-size species), frogs, crayfish, turtles, insects, etc., sometimes birds and small mammals. In coastal waters eats marine species (Bowyer et al. 1995). Commonly preys on nesting seabirds in some areas (e.g., Alaska islands). See Toweill and Tabor 1982 for many further details.
Adult Phenology: Circadian
Immature Phenology: Circadian
Phenology Comments: Active in winter, even in fresh deep snow. May be active at any time of day. In Idaho, most active from dawn to midmorning and in the evening (see Toweill and Tabor 1982).
Length: 131 centimeters
Weight: 13600 grams
Economic Attributes
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Economic Comments: Harvested for fur. In the early to mid-1970s, U.S. harvest was about 11,000-19,000, Canadian harvest was about 15,000-18,000 (Toweill and Tabor 1982). U.S. harvest recently has been largest in Louisiana (about 7500 pelts annually in the 1970s and early 1980s) (Shirley et al. 1988).
Management Summary
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Management Requirements: Suseptible to overharvest (Toweill and Tabor 1982).

See Berg (1982) for information on reintroduction. See Tango et al. (1991) for a review of information on reproduction by reintroduced otters. Sources of otters for reintroductions should be based on documented patterns of genetic variation, which do not concur very well with nominal subspecies delineations (Serfass et al. 1998).

Monitoring Requirements: Reid et al. (1987) discussed population estimation using snow tracks. Testa et al. (1994) described a method for estimating population size/density using radiotracer implants.
Management Research Needs: Refine techniques for successful reintroduction (e.g., reducing dispersal from reintroduction area).
Biological Research Needs: See element stewardship (ES) files.
Population/Occurrence Delineation
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Use Class: Not applicable
Minimum Criteria for an Occurrence: Evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals in appropriate habitat where the species is presumed to be established and breeding.
Separation Barriers: Rugged mountain ridges.
Alternate Separation Procedure: Occurrences generally should be based on major occupied hydrographic or ecogeographic units that are separated along areas of relatively low otter density or use. These units may be based on available sightings/records or on movements of radio-tagged individuals, or they may be based on the subjective determinations by biologists familiar with otters and their habitats. Where occupied habitat is exceptionally extensive and continuous, that habitat may be subdivided into multiple contiguous occurrences as long as that does not reduce the occurrence rank (i.e., do not split up an A occurrence into multiple occurrences that would be ranked less than A). The dividing lines should be made as much as possible along lines of limited otter use.
Separation Justification: Individual otters regularly move large distances. Home ranges are large and often generally linear along streams and shorelines, typically 30-50 kilometers long for males or pairs (Jackson 1961). Home range lengths at all seasons were 10-81 kilometers in Idaho (Melquist and Hornocker 1983); 20 kilometers of marine shoreline for males in Alaska, 10 kilometers for females (Bowyer et al. 1995); average of 32 km for 10 radio-tagged individuals in Colorado (Mack 1985). Young may disperse up to 200 km (Melquist and Hornocker 1983).

Thus populations and metapopulations generally occupy large areas. For this and other wide-ranging, low density mammals, it seems most reasonable to base occurrences (and conservation efforts) on major occupied landscape features rather than on specific prescribed separation distances.


Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 12 km
Inferred Minimum Extent Justification: An arbitrarily small distance, representing a small home range (See Separation Justification).
Date: 09Mar2005
Author: Hammerson, G., and S. Cannings
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 28Nov1995
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 16Dec1997
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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