background
It is common to see sea otters floating on their backs on the water and using stones to knock out shellfish to feed. Scientists say sea otters may have learned to use stones as tools long ago, and appear to predate other marine mammals. A genetic study that analyzed more than 100 sea otters living off the coast of California showed that sea otter ancestors had begun to exhibit such behaviors millions of years ago.
body
Sea otters are often seen floating on their backs hammering at clams with rocks. They break open the shells to reveal a tasty meal inside.
New research suggests, even the ancestors of sea otters living millions of years ago knew how to do this. That's according to a genetic study of otters living off the Californian coast.
They are not the only marine mammals to use tools. Dolphins in Australia have been seen to use sponges to protect their noses when scouting for fish on the sea floor. But in dolphins, this seems to be a relatively new invention, happening less than 200 years ago. Evidence, say the scientists, that sea otters are very smart and have a natural ability to use tools.
vocabulary
Sea otter sea otter
on one's back 仰面躺着
Hammer hammers and strikes hard
Genetic study Genetic research
Marine mammal marine mammal
sponge (natural) sponge
Scouting look, search
Invention spontaneous new behaviors, new activities
Natural ability innate ability, instinct