These very social, playful aquatic animals are members of the weasel family of the order Carnivora. Their bodies are highly modified for a life spent mostly in and around the water. These modifications include a streamlined body, webbed feet, thick, water-repelling, insulating fur, a tapered tail, and small ears and nasal openings that can close underwater!
Habitat and Range
These river otters live in mainly the northern U.S., the coastal states, and parts of Canada in and close by any inland waterways.
River otters will eat many different types of freshwater creatures including fish, crayfish, small mammals, frogs, mollusks, and other small invertebrates.
Females give birth to one to six young in their underground burrows. Males do not take part in the care of the young. After about 2 months of mainly being in the burrow, the mother pushes the young otters into the water, forcing them to learn how to swim while she supervises.
I looked at two current research articles on the North American River Otter, one explored the impact of an invasive trout species on the otter populations in Yellowstone National Park and the other was written about an attempt to reintroduce the river otters to waterways in Indiana.
The paper about the invasive species of Lake trout being found in increasing amounts in several lakes in Yellowstone National Park, revealed that although some other species of piscivores (fish-eaters) such as the grizzly bear and some birds are being impacted by the replacement of the endangered Yellowstone cutthroat trout with the invasive lake trout, the river otter is doing fine. The river otter eats a variety of different fish, so replacing one of its major food types with the invasive species of trout does not change anything except now more of the river otter's diet is made up of lake trout rather than the cutthroat trout.
The second paper spoke about the attempt to reintroduce the North American river otter to Indiana after the species had disappeared from the state in 1942 due to fur trapping, loss of habitat, and food. The attempt had mixed results in that many of the original otters introduced from surrounding states were killed by various means just as they were before. However, some good was achieved and many of the otters did begin breeding and establishing themselves in certain regions of the state. The paper stated that the researchers conducting this experiment did need to look further into ways to protect, maintain, and regulate these restored populations as well as defining the exact occupied regions and certain age-specific reproductive patterns.
2. Kelt, D; Johnson, M. (2010) Ecological consequences of invasive lake trout on river otters in Yellowstone National Park. BIOLOGICAL CONSERVATION, 143, 5, p. 1144-1153.
3. Walker, H; Hudson, C; Hewitt, T; Thompson, J. (2007) Prospects for restoring river otters in Indiana. Proceedings of the Indiana Academy of Science, 116, 1, p. 71-83.