Harbor Seals Essay example -- Animals Sea Wildlife Descriptive Essays

Harbor Seals Harbor seals are marine mammals that have spotted coats in a variety of shades from silver gray, black to dark brown. They reach 5 to 6 feet in length and weigh up to 300 pounds. Harbor seals are dimorphic, with the male being slightly larger than the female. They are true, or crawling seals, which means they have no external earflaps. True seals also have small flippers, and move on land by flopping along on their bellies. They breathe at the surface and hold their breath while diving. They can dive to 1,500 feet for up to 40 minutes, although their average dive lasts 3 to 7 minutes. Their scientific name basically means 'sea calf' or 'sea dog.' This nickname is fits them well, as these seals closely resemble a dog when their head is viewed at the surface of the water. When the harbor seal pup (baby seal) is born, it has a coat that closely resembles the adult coat. Some have a longer, softer white or gray coat (lanugo) when born, but they shed that coat within about 10 days. Harbor seals are found across the Northern Hemisphere in both the Atlantic and Pacific Oceans. In the northeast Pacific, they range from Alaska to Baja California, in Mexico. They live near-shore coastal waters and frequent sandy beaches, mudflats, bays, and estuaries. Some harbor seals even live in certain areas of Europe such as Finland. The total harbor seal population in the northeast Pacific is estimated to be 330,000, in California the estimated population was 40,000, and in Europe the estimated population was 6,000 in 1997. Harbor seals spend about half their time on land and half in water, and they sometimes sleep in water. They may sleep most of the day on the beach to keep safe from the predators that hunt them, and go into the water only a couple of times each day to hunt for food. Harbor seals don?t have a permanent place to live but they usually are found in small groups, but sometimes occur in numbers of up to 100 to 500. Their average life span is around 25 years, although some have lived for over 30 years. However, males seem to live shorter lives, probably because of the added physical stress of fighting during mating season.   Ã‚  Ã‚  Ã‚  Ã‚  The Harbor Seal is both a predator and a prey. They are very vital in the food chain. Seals eat a lot of fish and prevent over population, and they are a great source of food to animals such as orca whales, great... ... high tolerance to carbon dioxide in the tissues, they have the ability to store large amounts of oxygen in the muscle tissues, and they have the ability to make their lungs collapse when air is expelled before they dive, which helps to prevent the bends. To help see in dark and murky waters, the seals have special adapted eyes that make them able to see in such conditions. To guard against very cold water temperatures, harbor seals maintain a thick layer of fat beneath their skin, giving them a thick sausage shape. To make the harbor seals less noticeable to predators, their coats sometimes blend in with the rocks or sand they?re lying in. To help them find food easier, they have a keen sense of smell. Without these adaptations, who knows if the Harbor Seal would still exist today. Works Cited: *Hanan, D. (1999). Pacific Harbor Seals. Alolkoy Publishing Co. PP 12-59. *King, J. (1983). Seals of the World. British Museum (Natural History) and Cornell University Press. PP 20-26. *Internet: Sea World web site. www.seaworld.org/animal_bytes/harborsealab.html April 20, 2001 *Internet: The Marine Mammal Center web site. www.tmmc.org/harborsl.htm April 20, 2001