Otter Otters
- From: pokerverein@xxxxxxxxxxxxxx
- Date: Tue, 12 May 2009 23:31:27 -0700 (PDT)
Otter
Author Selzer-McKenzie
Otters are semi-aquatic (or in one case aquatic) fish-eating mammals.
The otter subfamily Lutrinae forms part of the family Mustelidae,
which also includes weasels, polecats, badgers, as well as others.
With thirteen species in seven genera, otters have an almost worldwide
distribution. They mainly eat aquatic animals, predominantly fish and
shellfish, but also other invertebrates, amphibians, birds and small
mammals.
The word otter derives from the Old English word otr, otor or oter.
This and cognate words in other Indo-European languages ultimately
stem from a root which also gave rise to the English words water, wet
and winter.
An otter's den is called a holt or couch. A male otter is a dog
(otter), a female a bitch (otter), and a baby a whelp or pup. The
collective nouns for otters are bevy, family, lodge or romp, being
descriptive of their often playful nature, or when in water raft
Otters have long, slim bodies and relatively short limbs, with webbed
paws. Most have sharp claws on their feet, and all except the sea
otter have long muscular tails.
They have a very soft underfur which is protected by their outer layer
of long guard hair. This traps a layer of air, and keeps them dry and
warm under water.
Many otters live in cold waters and have very high metabolic rates to
help keep them warm. Eurasian otters must eat 15% of their body-weight
a day, and sea otters 20 to 25%, depending on the temperature. In
water as warm as 10°C (50°F) an otter needs to catch 100 grams (3 oz)
of fish per hour to survive. Most species hunt for 3 to 5 hours a day,
and nursing mothers up to 8 hours a day.
For most otters, fish is the primary staple of their diet. This is
often supplemented by frogs, crayfish and crabs. Some otters are
expert at opening shellfish, and others will feed on available small
mammals or birds. Prey-dependence leaves otters very vulnerable to
prey depletion.
Otters are very active, chasing prey in the water or searching the
beds of rivers, lakes or the seas. Most species live beside water,
entering it mainly to hunt or travel, otherwise spending much of their
time on land to avoid their fur becoming waterlogged. The sea otter
does live in the sea for most of its life.
Otters are playful animals and appear to engage in various behaviors
for sheer enjoyment. Different species vary in their social structure,
with some being largely solitary, while others live in groups – in a
few species these groups may be fairly large.
The northern river otter (Lontra canadensis) became one of the major
animals hunted and trapped for fur in North America after European
contact. River otters eat a variety of fish and shellfish, as well as
small land mammals and birds. They grow to one metre (3 to 4 ft) in
length and weigh from five to fifteen kilograms (10 to 30 lb).
In some areas this is a protected species, and some places have otter
sanctuaries, which help sick and injured otters to recover.
Sea otters (Enhydra lutris) live along the Pacific coast of North
America. Their historic range included shallow waters of the Bering
Strait and Kamchatka, and as far south as Japan. Sea otters have some
200 thousand strands of hair per square centimetre of skin, a rich fur
for which humans hunted them almost to extinction. By the time the
1911 Fur Seal Treaty gave them protection, so few sea otters remained
that the fur trade had become unprofitable. Sea otters eat shellfish
and other invertebrates (especially clams, abalone, and sea urchins),
frequently using rocks as crude tools to smash open shells. They grow
to 1.0 to 1.5 metres (2.5 to 5 ft) in length and weigh 30 kilograms
(65 lb). Although once near extinction, they have begun to spread
again, from remnant populations in California and Alaska.
Unlike most marine mammals (such as seals or whales), sea otters do
not have a layer of insulating blubber. As with other species of
otter, they rely on a layer of air trapped in their fur, which they
keep topped up by blowing into the fur from their mouths. They spend
most of their time in the water, whereas other otters spend much of
their time on land.
This species (Lutra lutra) inhabits Europe, and its range also extends
across most of Asia and parts of North Africa. In the British Isles
they occurred commonly as recently as the 1950s, but became rare in
many areas due to the use of chlorinated hydrocarbon pesticides and as
a result of habitat-loss and water pollution (they remained relatively
common in parts of Scotland and Ireland). Population levels attained a
low point in the 1980s, but are now recovering strongly. The UK
Biodiversity Action Plan envisages the re-establishment of otters by
2010 in all the UK rivers and coastal areas that they inhabited in
1960. Roadkill deaths have become one of the significant threats to
the success of their re-establishment.
The giant otter (Pteronura brasiliensis) inhabits South America,
especially the Amazon river basin, but is becoming increasingly rare
due to poaching, habitat loss, and the use of mercury and other toxins
in illegal alluvial gold mining. This gregarious animal grows to a
length of up to 1.8 metres (6 ft), and is more aquatic than most other
otters.
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