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About Harbor Seals
(C) LJFS and Liesl Schindler
“Although seals are highly adapted to their aquatic way of life, there are still aspects of their life cycle for which they have to come ashore. The annual molt is one such event and it is of crucial importance because a seal’s skin and fur are essential for waterproofing and temperature control. The true seals, such as harbor seals, molt their fur relatively quickly about one month after the breeding season. At this time of the year, some seals spend a particularly large amount of time ashore and spend little or no time feeding, but the reasons for this are not entirely clear. The most likely explanation is that by staying ashore, they minimize heat loss and maintain a relatively high temperature which encourages blood flow close to the skin, thus accelerating the molting process.
Seals spend varying periods hauled out at other times of the year for reasons entirely unconnected with molting or breeding but the purpose for this is not known. Contrary to popular belief they are not simply basking in the sun because seals in temperate regions haul-out regularly even on the coldest winter days, and seals in polar regions remain hauled out on the ice despite the most ferocious storms.”
Miller, David, Seals and Sea Lions, 1998, World life Library, Voyageur Press, 0. 39
- Harbor seals are a coastal, nearshore species of marine mammal of the order of pinnipedia, and are an integral part of the marine environment.
- They must haul-out (come out of the water onto dry land) each day in order to survive. Between 30% and 40% of their time is spent in this way. They haul-out at the Casa Beach year round. This harbor seal colony numbers approximately 200 seals. Harbor seals communicate with each other using body postures and are the most docile and least vocal of all pinnipeds. Mature female harbor seals give birth to one pup each year. Pup mortality is high: up to 50%.Mother seals prefer to give birth on land. Seal pups have been born on the Casa Beach for a number of years. Pupping season is February through April. Harbor seal pups nurse on their mother's milk for 4 - 8 weeks, after which they are weaned. In their early weeks of life, mother harbor seals may carry their pups on their backs while swimming and diving. Harbor seals molt annually from mid-June to mid-August, and shed all of their fur. The average lifespan of a harbor seal is 20 – 25 years. After mating there is a natural two-month period of delayed embryo implantation. They then carry their young for nine months. Harbor seals do not drink water; they metabolize water from their food. Seals can rest underwater. Seals' lungs collapse when they dive, their heart rate slows dramatically, and blood flow to some organs is restricted. In this way their bodies conserve oxygen and prevent the "bends. "Seals dive repeatedly for short periods but can dive up to 600 feet and hold their breath under water for as long as 30 minutes.
- "Seal pollution" is a myth. Seals are a natural part of the marine environment. This stretch of local coastline is actually polluted by humans - that means us! Frequent sewage spills and storm drain run-off is a serious threat to the health of the oceans and the countless life forms who live there.
Harbor seals spend their entire lives along the same stretch of coastline. Seals maintain a thick layer of fat beneath their skin to guard against cold water temperatures, giving them a thick sausage shape. They spend many hours during the day hauled out on a favorite sandbar or rocky island soaking in the warm sunshine. Harbor seals are opportunistic feeders who tend to hunt for fish, cephalopods, and other invertebrates during high tide. Harbor seals are most vulnerable when out of the water and will quickly swim off if you get too close. Harbor seals give birth to one pup in the spring. Pups can be born on land or in the water, and the nursing period lasts about six weeks. After nursing is complete, the adult seals mate. Pregnancy lasts nine months, but the fertilized egg does not begin to develop for two months, aligning birth dates to the same time each year.
Harbor seals can be seen year round at Casa Beach and Seal Rock at the foot of Jenner St. and Coast Blvd. in La Jolla. It is very rare for harbor seals to choose a haul-out site so close to humans, making this a rare natural treasure, indeed.
Copyright (C) 2001-2013 La Jolla Friends of the Seals
P.O. Box 2016, La Jolla, CA 92038
For more information please email us.