七年级
Blue whales are coming back
发布日期 : 2016-05-04浏览次数 : 来源 :
Some blue whales living in the Pacific Ocean used to travel north toward Alaska every spring. However, around the 1960s, they stopped making the trip north. Now, after more than 40 years, scientists find that blue whales are back to the northern waters again.
Blue whales are the largest animals in the world, but being large has not kept them safe.
For many years, blue whales living in the Pacific Ocean have not swum north. Then, in 2004, people saw three blue whales in the water of Alaska. Scientists think they traveled north to look for food. Blue whales eat four tons(吨)of krill(磷虾)every day. A change in ocean temperature may have pushed the krill farther north. When blue whales can’t find food, they swim far away. So they are back again.
Blue whales are the largest animals in the world, but being large has not kept them safe.
For many years, blue whales living in the Pacific Ocean have not swum north. Then, in 2004, people saw three blue whales in the water of Alaska. Scientists think they traveled north to look for food. Blue whales eat four tons(吨)of krill(磷虾)every day. A change in ocean temperature may have pushed the krill farther north. When blue whales can’t find food, they swim far away. So they are back again.