Habitat & Distribution

Otters

Habitat & Distribution

Distribution

  1. Otters are widely distributed. They are found on all continents except Australia and Antarctica.
  2. North America.
    • North American river otters are found throughout the United States and Canada.
    • Sea otters inhabit coastal areas and islands of the eastern and western North Pacific Ocean.
      • Alaska sea otters inhabit the coast of Alaska, including the Aleutian Islands, and south along British Columbia and Washington.
      • The range of the Russian or Asian sea otter extends from northern Hokkaido, Japan to the Commander Islands in the western North Pacific.
      • California sea otters are found off the coast of central California; between Half Moon Bay and Pt. Conception. There is also a small experimental population that originated from relocated animals at San Miguel Island off the coast of Santa Barbara.
      • Historically, sea otters occupied a contiguous range from northern Japan, across the North Pacific, and down to Baja California, Mexico. They were hunted nearly to extinction, but conservation measures have allowed some populations to recover.
  3. South America.
    • Marine otters live along the Pacific coast of South America, ranging from northern Peru to Tierra del Fuego.
    • Neotropical otters range from Uruguay north to Central America and Mexico.
    • Southern river otters are found in Argentina and Chile.
    • Giant otters are found throughout almost all of South America.
  4. Africa.
    • Cape clawless otters inhabit the southern two-thirds of the African continent.
    • Congo clawless otters inhabit equatorial Africa, from southeastern Nigeria to Gabon, down to Uganda and Burundi.
    • Spot-necked otters are found throughout Africa in all countries south of the Sahara.
  5. Eurasia.
    • Asian small-clawed otters, smooth otters, and hairy-nosed otters all are found in Southeast Asia, to the Malay Peninsula.
    • Eurasian otters are found throughout most of Europe, Asia, and North Africa (Morocco, Algeria, and Tunisia).

Habitat

  1. Otters are usually found no more than a few hundred meters from water. Most species are entirely dependent on aquatic habitats for food.
    • River otters (genus Lutra) inhabit all types of inland waterways, as well as estuaries and marine coves. In southern Chile the marine otter is found almost exclusively along exposed rocky seashores; farther north it may inhabit estuaries and fresh water.
    • Giant otters (genus Pteronura) are found mainly in slow-moving rivers and creeks within forests, swamps, and marshes. They prefer waterways that have gently sloping banks and good cover.
    • Clawless otter (genus Aonyx) habitats vary greatly among the species and between individuals.
      • Asian small-clawed otters occur in fresh and brackish water habitats including rivers, creeks, estuaries, and coastal waters.
      • Congo clawless otters appear to inhabit only small, torrential mountain streams in heavy rainforest areas. They are thought to be more terrestrial in nature than other otter species.
      • Cape clawless otters are found in widely varying habitats, from dense rainforest to open coastal plain and semi-arid zones. Most seem to prefer quiet ponds and sluggish streams. In coastal areas, they are known to forage both at sea and in adjoining streams and marshes.
    • Sea otters (genus Enhydra) are found in coastal waters of the North Pacific, rarely more than 1 km (0.6 mi.) from shore.
      • They are capable of spending their entire life at sea, but sometimes rest on rocky shores. The Alaska otter has a greater tendency to haul out (come to shore) than the California otter.
      • California otters often prefer kelp beds, probably because of the protection and food resources they provide.
  2. With the exception of sea otters, all otters spend a great deal of time on land, often traveling considerable distances between waterways.
    • Most otter species have at least one permanent burrow (den) by water. The burrow's main entrance may be under water. It then slopes upward to a nest chamber above the high-water level. River otters dig their own burrows.
    • Cape clawless otters do not dig burrows. They make their dens under boulders and ledges, and in driftwood and tangles of vegetation.
    • Besides burrows, many river otters establish and use a variety of land "facilities" for a number of their daily activities.
      • Rolling places are bare patches of ground where otters roll and groom.
      • Slides offer quick access to water or other facilities. Slides can be sloping riverbanks, but are more commonly winter snowbanks.
      • Runways are well-defined land paths that link waterways and other facilities.
      • Spraint stations are areas designated by otters for routine, systematic defecation.

Home Ranges

  1. A home range is the portion of land and water that an animal frequently visits during its daily and seasonal activities.
  2. All otter species occupy a home range.
  3. Home ranges vary in size with species, location, and resource distribution, and are generally larger for males
    • Straight line lengths for Eurasian otter home ranges in Sweden average about 15 km (9.3 mi.) for males and about 7 km (4.3 mi.) for females. A male's range often overlaps that of one or more females.
    • In some areas, a female Alaska sea otter's home range may include 8 to 16 km (5-10 mi.) of coastline.
  4. Territories differ from home ranges. Territories are generally smaller than home ranges. Otters mark their territories with scent. Same-sex territories do not overlap, and they are patrolled and defended by their owners.

Migration

  1. Many otter species undergo seasonal movements, but no extensive migrations.

Population

  1. Very little information is available on worldwide population figures for freshwater otters. Most otters have widespread distributions, but relatively sparse populations. Nearly all otter populations have been impacted to some extent by human activities.
  2. There may be fewer than 1,000 marine otters left throughout their range.
  3. The Alaskan sea otter population numbered more than 100,000 in the 1980s. Since the 1990s, the southwestern stock of Alaskan sea otters has experienced a dramatic (up to 70% population) decline, most likely due to increased predation by killer whales. The decline in more typical killer whale prey species has led some killer whales to switch to feeding on sea otters.
  4. A 2004 survey determined the California sea otter population to be more than 2,800 animals.