- Published: 17 December 2008
- Hits: 2689
Larry McCreary, age 9, of Chattanooga, Tenn., for his question:
WHY DO SEALS MIGRATE?
Northern fur seals migrate or travel about 5,000 miles each year. They travel farther than any other mammal with their yearly trips. Scientists have no idea why the seals make these annual journeys.
Seals are excellent swimmers and spend most of their time i n water. But they give birth to their young on land. Harbor seals and ringed seals spend much of their time on land or on floating chunks of ice, but they are never far away from water.
Northern seals swim south from the Bering Sea almost to northern Mexico, and then return north again. During the entire 5,000 mile trip, the seals swim 10 to 100 miles from the coast and never go ashore.
while some mammals migrate each year as part of their reproduction schedule, this does.not seem to be the reason in the seal's case. The animals with bodies shaped like torpedos just seem to have some secret reason for wanting to take a long swim each year.
Most kinds of seals live in groups and may stay together on long ocean voyages. A few species, including the Ross seals of the Antarctic, live alone or with only two or three other seals.
Every spring, seals go to their breeding grounds, called rookeries, to have young and to find mates. Most rookeries are on islands. Rookeries of northern fur seals are large beach areas where more than 150,000 seals may gather at one rookery.
Male seals, called bulls, arrive at the rookeries late in may and fight for choice places on the beach, called territories. The females, called cows, come ashore in July. A group of cows, called a harem, join one of the bulls. A harem may have from three to 40 cows. A few bulls may have over 200 cows.
Babies are born shortly after the cows arrive since they have carried the young i n their bodies for 1 2 months. The cows mate again a few days after they give birth.
Most cow seals bear their first young when they are about five years old, and they may give birth each year until they are 13. Some cow seals may bear young until they are 20 or older.
A female seal almost always has one baby at a time. The baby is called a pup.
A newborn pup has all of its teeth and a fine, soft covering of fur. Sea lion pups have brown fur and newborn fur seals, elephant seals and monk seals have black coats.
Northern fur seal pups can swim and can travel on land from the moment they are born. The mothers divide their time between eating at sea and nursing their pups on land.
A mother, may stay at sea from seven to nine days. After she returns, she hunts for her pup among the hundreds of others on the beach. Each mother feeds only her own pup, which she recognizes by its cry and its odor.
A pup then gets enough milk to stay alive unti1 it is next feeding, which might be another week or so.
A pup weighs about 10 pounds at birth and from 30 to 35 pounds when its mother leaves it, three or four months later.