The Elephant Seal Life Cycle

Elephant Seals spend 80% of their lives in the open ocean and range from Mexico to Alaska in search of food. One seal that was tagged in Point Reyes was even seen in Russia. Not only do they spend almost all of their time at sea they spend 90% of the time at sea underwater in search of food, resting, or just moving from place to place. Elephant seals dive deeper than most marine mammal diving an average of 1000 to 2000 feet and sometimes as deep as a mile. This dive lasts up to ninety minutes and is followed by about ten minutes resting on the surface breathing. The seals prefer the depths because they are below the radar of their natural predators. Although no one knows for sure it is speculated that they are able to feed the deeply because they have no competition, and their large eyes and the bioluminescence of their prey allows them to easily find food. It is also speculated that their whiskers, which are up to eight inches long also help them search for rays, rockfish, ratfish, and other delicacies on the ocean floor. Elephant seals are able to dive this deep because they carry the oxygen they need to survive in their muscles rather than in their lungs. After breathing, the seal exhales and collapses its lungs. As they begin to dive their fat also compresses allowing them to dive quickly with little effort.(Sarah Allen Interview) The seal are able to spend so much time under water because they have the ability to slow their heart rate from 55-120 beats per minute down to 4-15 beats per minute. The seal’s blood pressure remains normal because it is able to cut off blood supplies to its extremities supplying mainly its brain and vital organs.(Nps.gov/pore) During adult migrations the male and female seals travel thousands of miles apart and follow different feeding patterns. The males often return to the Aleutian Islands to feed each year, while the females generally feed in small eddies in the northwest Pacific and off the Hawaiian Islands. However the seals often break this pattern, sometimes feeding in the north Pacific Gyre. Males dive deeply and repeatedly for food for the first three weeks, females also dive deeply, but tend to travel deeper during the day. Generally the females tend to feed mostly on squid in the mid-water, while the males feed mostly on bottom fish and octopus. They have gastroliths in their stomach, small rocks that serve to break down bone matter. The seals feed, diving repeatedly for four to five months of the summer and fall. The seals do not sleep but rather take catnaps as they dive. They spend the majority of their lives under water and therefore are rarely seen in the open ocean. Currently there are about 500 elephant seals that have been tagged with GPS units that also record water temperature and depth.(Nps.gov.pore) This provides “3 dimensional imaging of what the seals are doing” and can be viewed at http://www.topp.org/species/elephant_seals. There is still much to be discovered about these fascinating creatures.