Southern Elephant Seal: The World's Largest Seal

Elephant seals, which live in the icy waters of the Antarctic and subantarctic regions, feed only in the sea and spend up to ten months of the year hunting fish and squid. They usually dive for 20 to 30 minutes, but can stay underwater for up to two hours and reach depths of over 2,000 meters. 

Before diving, they exhale, in order to eliminate gases that could cause nausea. To better obtain oxygen, their red blood cells have twice as much hemoglobin as land animals of the same size, and their muscles store none. In addition, their heart rate slows to 5 to 15 beats per minute, so that blood flows only to the vital organs. They have poor eyesight in daylight, but can see well in deep, dark water. Their eyes are highly sensitive to the wavelengths emitted by bioluminescent lanternfish, their main food source. 

The long hunting seasons allow them to build up enough fat to spend two extended periods of time on land: the moult, which lasts a month in January and February, and the breeding season, which begins around mid-August. They return to the same location each year, with males spending weeks or months fighting over harems of females, with whom they then mate. The largest males surround themselves with more than 50 females.

Below, a southern elephant seal hauls itself out onto the island of South Georgia, which is also home to a large colony of breeding penguins. More than 50 percent of the global population of these seals breed on this island.