Otters are found on every continent except Australia and Antarctica. There are 13 species ranging from the Asian small-clawed otter to the giant river otter of South America. Though most live in freshwater rivers, lakes, and wetlands, the sea otter and the smaller marine otter are found in the Pacific Ocean.
Most species are small, with short ears and noses, elongated bodies, long tails, and soft, dense fur. They have very specific physical adaptations which help them to thrive within their natural environment including webbed feet and powerful tails which make them very strong swimmers. Their nostrils and ears close to keep water out, and waterproof fur keeps them warm. Otters have the densest fur of any animal, as many as a million hairs per square inch in places
All otters are expert hunters that eat fish, crustaceans, and other animals, and sea otters have an ingenious method to open shellfish. A sea otter may float on its back, place a rock on its chest, then smash the mollusk down on it until it breaks open, or they will smash mollusks against rocks either under the water or at the water’s edge, and individuals have preferred rocks which they use consistently.
An analysis of discarded mussel shells has shown consistent cracks along the same side suggesting that most otters are in fact right-handed. It was previously thought that only great apes and humans had a preferred “hand,” but recent research has expanded this to many other animals including sea otters.
Tool use has been found among only a few marine animals, including dolphins, which use sponges to protect their beaks while hunting fish in coral—and possibly as love tokens.
Like sea otters, tusk fish also smash any hard-shelled prey such as sea urchins, against their favourite stationary stones.
Tools use in sea otters also appears to be an innate behaviour in all young sea otters. Orphaned otter pups raised in captivity exhibit rudimentary pounding behaviour without training or previous experience, and wild pups develop tool-use behaviour before weaning regardless of their mother's diet type and feeding behaviours.
Otters really are amazing animals
Otters were once hunted extensively for their fur, many to the point of near extinction. Despite regulations designed to protect them, many species remain at risk from pollution and habitat loss. The sea otter is listed as endangered on the IUCN Red List, pressured by pollution, pesticides, and conflicts with fishermen who kill them for eating their fish. Asian otter species also face severe threats from the illegal pet trade.
Sea otters are a keystone species because of their critical importance to the health and stability of the nearshore marine ecosystem. They eat sea urchins and other invertebrates that graze on giant kelp. Without sea otters, these grazing animals can destroy kelp forests and consequently the wide diversity of animals that depend upon kelp habitat for survival. Additionally, kelp forests protect coastlines from storm surge and absorb vast amounts of harmful carbon dioxide from the atmosphere.
Sea otters are threatened by pathogens and parasites, food availability, nutritional deficiencies, habitat degradation, coastal pollutants and contaminant exposure are among many of the contributing factors threatening the recovery of the species. And the risk of a major oil spill remains a serious threat.