Recently more Harp and Hooded seals than usual have been found stranded along the East Coast of the United States as far south as the Carolinas and the U.S. Virgin Islands. These stranded seals should have migrated much farther north by this time of year. A recent study indicates the problem is in part due to the decline in ice cover.
The Harp SealPagophilus groenlandicus, also known as the Saddleback Seal, lives in the north Atlantic Ocean and the Artic Ocean. Their scientific name translates to “ice-lover from Greenland,” and they really do love ice! Having a thick layer of blubber and efficient flippers which they can use as heat exchangers, they can efficiently regulate their temperature on ice and in extremely cold water. They have all-black eyes with grayish-silver bodies. Adult harp seals can weigh from 300-400 pounds.
The Hooded SealCystophora cristata is also found primarily in the North Atlantic Ocean. They are listed as Vulnerable on the IUCN Red List. What stands out on these seals is a bulge on the males heads which develops around four years of age. This bulge is actually an inflated air sac or “hood” above their noses and is used in mating rituals. Adult males can weigh up to 900 pounds! That’s a big seal!
In general, these seals reproduce in the spring on huge masses of ice. As spring turns to summer the seals begin to migrate North. It is believed that a seals sight is very helpful in helping it navigate, making vision one of their most important senses.
Increasing numbers of Hooded Seals are being found dead or unhealthy on beaches further south than where they should be. Usually around 25 to 35 stranded seals are found on the Northeast Coast, however this year a total of 55 stranded seals have been found in both the Northeast and Southeast coasts combined. According to biologist Ulrika Malone, the seals are found dehydrated, sunburned, and suffering from heat exhaustion and hair loss. The ones that are alive are taken into rehabilitation centers by wildlife officials. The seals are nursed back to health and then released back into the wild.
A recent study published in the PLOS ONE journal confirms the theory that receding ice levels are at least partially to blame for more seals being found stranded. Most of the stranded seals are young, with 62% of them being male. It is thought that the majority are males because of their tendency to wander further away once they head off by themselves. Genetic issues, such as inbreeding, were mostly excluded as reasons. It was found that the stranded seals were just as genetically diverse as seals which were not stranded.
Sea ice is a prominent part of seal life and reproduction. Every spring (March-April) the seals reproduce on the ice drifts. The mothers nurse the young for a short time before they are left on their own to start their journey north. In the past 30 years ice cover in April has declined about 8%, which is significant. Researchers believe this affects the seals because there isn’t enough space on the ice for all the new young seals. Some of the babies may then be forced into the water prematurely and become confused as to which direction they should go. They may follow large groups of fish moving south instead of north and completely lose their way.
If the amount of sea ice continues to decline, it could cause serious problems for many types of seals, especially the ones who use the ice masses to reproduce. In fact, Ringed Seals and Bearded Seals are already listed as threatened species due to this decline in ice cover.
Should we be concerned with ice cover decline? What do you think?