背景
人們經常能看到海獺仰面浮在水上用石頭敲開貝殼類動物進食的場景。科學家說，海獺可能很久以前就已經學會把石頭當作工具使用了，而且似乎比其它的海洋哺乳動物都要早。一項遺傳研究分析了在加利福尼亞海岸附近生活的 100多隻海獺，結果表明，在幾百萬年前海獺的祖先就已經開始表現出這類行為了。
正文
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.
詞彙
sea otter 海獺
on one's back 仰面躺着
hammer 用力錘打、敲擊
genetic study 遺傳研究
marine mammal 海洋哺乳動物
sponge （天然）海綿
scouting 尋找，搜尋
invention 自發的新行為、新活動
natural ability 天生的能力，本能