Types of Otters
There are 13 recognized species of otters, including 11 freshwater species and two saltwater species. The freshwater species, often referred to as river otters, are found throughout much of the world, including North America, South America, Europe, Africa, and Asia. They’re commonly found in freshwater ecosystems that offer a variety of prey, like fish, crayfish, crabs, mussels, and frogs.
As opportunistic hunters, they feed on whatever prey is most easily attained using a variety of methods. In addition to chasing fish, they use their manual dexterity to dislodge crabs and crayfish from underneath rocks. They also have sensory hairs on the snout called vibrissae that help them find prey by sensing water turbulence. While most of their travel is aquatic, they can also move swiftly on land and will do so if they need to move between bodies of water.
The two saltwater species are less widely distributed. The sea otter is found on the Pacific Coast of North America and much smaller marine otter lives on the coast of Peru and Chile. While the marine otter tends to stay close to land (typically within 100 meters of the shore), the sea otter has been known to travel much farther offshore. They prey on fish, sea urchins, crabs, and other shellfish, using rocks to break open their shells.
Otters have a number of adaptations that make them uniquely suited to aquatic environments. Their webbed feet and powerful tails make them strong swimmers, and their nostrils and ears can close to keep water out. While they aren’t covered in a fatty layer for warmth like other aquatic creatures, they have the densest fur of any animal, with as many as a million hairs per square inch in some places. To keep their fur waterproof, they carefully groom themselves to stay clean.
Sea otters have developed several methods for ensuring they’re able to sleep on the open water without drifting away. They will often entangle themselves in kelp to keep themselves in place. Sometimes they’ll also intertwine their feet with another sea otter so they’re able to stick together. They can link together to create large “rafts” or “pods,” that can be made up of up to 1,000 individuals.
While river otters commonly live alone or in pairs, they are especially playful and often socialize in groups. They’re frequently seen twisting, rolling, diving, and splashing in the water. They’ve also been known to slide or burrow in the mud or snow. It’s believed that these playful activities also serve practical purposes by strengthening social bonds, improving hunting techniques, and leaving scents that mark territory.
Otters are considered a keystone species, meaning that they’re critical to the ecosystem in which they live due to their large-scale impact on the environment. Along the Pacific coast, sea otters serve a particularly important role in controlling the sea urchin population which helps prevent kelp forests from becoming overgrazed. In California, research has also shown that their presence enhances seagrass beds.
According to the International Union for Conservation of Nature and Natural Resources (IUCN), about half of all otter species are threatened. The animals face increasing threats due to urbanization and logging practices. The destruction of wetland habitats and pollution are also serious problems both for the animals themselves and their prey.
In the past, otters and their mustelid relatives were hunted extensively for their fur, many to the point of near extinction. However, sea otters have since been protected by the International Fur Seal Treaty in 1911. In the US, they also received further protection with the passage of the Marine Mammal Protection Act and the Endangered Species Act in the 1970s.
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