Otters play an important part in river ecosystems as well. They are predators, which means they help regulate the numbers of the food species on which they feed. This has an impact on the ecosystem as a whole, and their presence indicates that the ecosystem is healthy. Otters eat aquatic insects, worms, and small fish. Because of this, they contribute to the digestion process by recycling nutrients and removing harmful substances from the environment. Otters also wash themselves with water to remove dirt and parasites from their coats. This helps keep them healthy. Otters' diets vary depending on what part of the world they are in. In freshwater environments such as lakes and rivers, they usually focus on invertebrates - animals without backbones such as crabs, crayfish, earthworms, and insect larvae. In saltwater environments such as the ocean, they eat fish. Otters use their sense of smell very effectively to find food. They will roam along shorelines looking for signs of life including rotting trees, ponds, and other bodies of water. When they find something interesting, they will swim up to it and take a closer look with their eyes before deciding whether or not to eat it. If you see an otter in the wild, take a moment to appreciate its beauty and know that it plays an important role in maintaining a healthy ecosystem.