What is threatening the grey whales?

The grey whale lived around 300 years ago in the Atlantic and Pacific Oceans. The giant animals were hunted extensively for their meat and oil. They became extinct in the Atlantic by the end of the 17th century, but can still be found in the Pacific Ocean. Around 20,000 animals migrate every year in October from Alaska in the north to the coast of Mexico, where they give birth to their young ones in winter. In west pacific, there are at most 200 grey whales at present and they are listed as critically endangered. These animals are sensitive to noise and are being displaced from their habitat because of the construction of drilling rigs for the crude oil industry.