While many scientists believe that tool use among dolphins is a relatively new phenomenon, a 2017 study published in Biology Letters suggests that otters may have been using tools for millions of years. Sea otters frequently use rocks to break open well-armored prey, such as snails.

While many scientists believe that tool use among dolphins is a relatively new phenomenon, a 2017 study published in Biology Letters suggests that otters may have been using tools for millions of years. Sea otters frequently use rocks to break open well-armored prey, such as snails.