Fourteen otter species, all built to slide
Otters are the water-going branch of the weasel family, fourteen living species at home in rivers and seas. Thick fur keeps them warm and afloat, webbed feet drive them, and they seem to play for fun, sliding down mud chutes and juggling small stones.
Their subfamily, Lutrinae, sits within the Mustelidae alongside weasels, badgers, mink and wolverines. The lineage began in the Early Miocene with Mionictis, descended from badgers that took to semi-aquatic life. Otters have long, slender bodies on short legs, powerful webbed feet and a seal-like ability to hold their breath. Every species except the sea otter has a long, muscular tail. Adults range from about 0.6 to 1.8 metres and from roughly 1 to 45 kilograms, with the Asian small-clawed otter smallest and the giant and sea otters largest.
Staying warm is expensive. Species in cold water run a high metabolism, so a Eurasian otter must eat around 15 per cent of its weight every day and a sea otter 20 to 25 per cent. In water of about 10 °C an otter needs roughly 100 grams of fish an hour, and most spend three to five hours a day hunting, nursing mothers up to eight. Fish is the staple, topped up with frogs, crayfish, crabs, small mammals or birds, which leaves otters exposed when prey runs short. Sea otters crack clams and urchins against stones balanced on their bellies, a trick the young must learn.
River otters mostly stay on land to keep their fur from getting waterlogged, entering the water to hunt or travel, while sea otters spend most of their lives at sea. After a pregnancy of 60 to 86 days, pups are raised in a holt beneath tree roots or a rocky cairn, lined with moss and grass, and cared for by both parents and older siblings. They leave the den at a month, swim at two months and stay about a year; females mature at around two, males at three, and otters can reach 16.
The English name comes from Old English otor, from the same ancient root that gave us “water.” People have hunted otters for fur and, in southern Bangladesh, fished with them. The Japanese otter is thought to have died out around 1979.
Source: Otter
