How do river otters differ from sea otters in body shape?

River otters and sea otters differ significantly in their physical build and proportions. While both are members of the Mustelidae family, their body shapes have adapted to their respective environments.1

• Build: River otters possess a sleeker, more slender build compared to the heftier sea otter.1
• Body Length: Sea otters have longer bodies than river otters.1
• Tail Shape: River otters have long, pointed tails that can account for approximately one-third of their total body length. In contrast, sea otters have shorter, flatter tails.1
• Locomotion: These physical differences influence how they move through the water. River otters utilize their long, pointed tails and all four paws to swim, whereas sea otters rely primarily on their short, flat tails and two back paws for navigation.1

Additionally, sea otters are significantly heavier than river otters, with males reaching up to 41 kg (90 pounds), while river otters typically weigh between 4.5 and 15 kg (10–33 pounds).1