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 The otter (lutrinae) is a
carnivorous aquatic
or marine mammal
part of the family Mustelidae,
which also includes weasels, polecats, badgers,
as well as others. The
otter is a large predator that is very rarely seen. It is a
fish-eating animal that is highly adapted for swimming and is found
in lochs, rivers and seas.
The collective
noun romp is used to refer to a group of otters.
Otters
have a dense layer (1,000 hairs/mm², 650,000 hairs per sq. in) of very
soft underfur
which, protected by their outer layer of long guard
hairs, keeps them dry under water and traps a layer of air to keep
them warm. All
otters have long, slim, streamlined bodies of extraordinary grace and
flexibility, and short limbs; in most cases they have webbed paws with sharp claws to grasp
prey.
In populated areas otters are nocturnal; however, on the coast
and in remote areas they also fish during the day.
Most
otters have fish
as the primary item in their diet, supplemented by frogs, crayfish
and crabs;
some have become expert at opening shellfish,
and others will take any available small mammals or birds. This
prey-dependence leaves otters very vulnerable to prey depletion.
To
survive in the cold waters where many otters live, they do not depend on
their specialised fur alone: they have very high metabolic
rates and burn up energy at a profligate pace: Eurasian
otters, for example, must eat 15% of their body-weight a day; sea
otters, 20 to 25%, depending on the temperature. In water as warm as
10°C an otter needs to catch 100 g of fish per hour: less than that and
it cannot survive. Most species hunt for 3 to 5 hours a day, nursing
mothers up to 8 hours a day.
River otters eat a variety
of fish and shellfish, as well as small land mammals and birds.
They grow to 1 m (3 to 4 feet) in length and weigh from 5 to 15 kg (10 to
30 pounds).
Sea otters have some 200,000
hairs
per square cm of skin,
a rich fur for which humans hunted them almost to extinction. Sea
otters eat shellfish and other invertebrates
(especially clams, abalone,
and sea
urchins ), and one can frequently observe them using rocks as crude tools
to smash open shells.
They grow to 1 to 2 m (2.5 to 6 feet) in length and weigh 30 kg (25 to 60
pounds). Unlike
most marine mammals (seals,
for example, or whales),
sea otters do not have a layer of insulating blubber.
As with other species of otter, they rely on air-pockets trapped in their
fur.
The otter has declined in numbers since the 1950s due to
pesticides entering the food chain. In many parts of the United
Kingdom it became extinct. Otters in Scotland suffered far less than
elsewhere and recent surveys have shown that numbers are increasing
throughout the country.
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