A Southern Ocean elephant seal wears a sensor on its head as it sleeps on an island in the Southern Ocean, Antarctica in this handout photo taken Feb 27, 2012. Elephant seals wearing head sensors and swimming deep beneath Antarctic ice have helped scientists better understand how the ocean's coldest, deepest waters are formed, providing vital clues to understanding its role in the world's climate. The tagged seals, along with sophisticated satellite data and moorings in ocean canyons, all played a role in providing data from the extreme Antarctic environment, where observations are very rare and ships could not go, said researchers at the Antarctic Climate & Ecosystem CRC in Tasmania. The sensor weighs about 100 to 200 grams and has a small satellite relay which transmits data on a daily basis. Picture taken Feb 27, 2012.[Photo/Agencies]