How do river otters use their tails differently from sea otters?

River otters and sea otters utilize their tails differently to navigate their respective environments:

• River otters: These animals possess long, pointed tails that can make up about one-third of their total body length. They use these tails in conjunction with all four of their paws to propel themselves through the water.1
• Sea otters: In contrast, sea otters have shorter, flat tails. They rely primarily on these tails and their two back paws for navigation while swimming.1

While many aquatic mammals, including otters, generally feature flattened tails to assist with movement, the specific reliance on the tail as a primary propulsive unit versus a steering or secondary aid varies between these two groups based on their distinct physical builds and habitats.12