The Seal Deal: Part 1 of series explores the pinniped world at Children’s Pool in La Jolla
By Ashley Mackin
The presence of harbor seals at the Children’s Pool in La Jolla generates a lot of interest … and a lot of controversy. Visitors and residents alike have questions about the seals, and much misinformation abounds.
In the interest of setting the record straight, La Jolla Light reached out to a seal expert for all the information we could gather about them. Marine biologist Monica DeAngelis, with the National Oceanic and Atmospheric Administration (NOAA) Federal Advisory Committee, answered our questions and those sent in by our readers. DeAngelis said a surprising amount is still unknown about harbor seals, and much depends on their environment. This will continue to make life at the Children’s Pool a hot topic for both visitors and scientists.
In the first of a three-part series, the Light will address birth facts, the first few weeks of life, the roles of family members, mortality rates, population issues and diet.
In the second installment, DeAngelis and representatives from SeaWorld will talk about seal mating and pregnancy, as well as SeaWorld’s involvement with the pinniped (fin-footed mammals) population at the Children’s Pool.
Keep calling in or e-mailing your questions, we’ll bring you a fourth part should the need arise. Questions? E-mail them to: firstname.lastname@example.org
Seal Birth Facts
■ Weight at birth: 18-26 pounds
■ Abilities at birth: Swim, see, bark and nurse.
■ How mother and pup bond: Scientists think they connect by barking. Soon after birth, barks and whimpers can be heard between mother and pup.
■ Physical characteristics: Seals are born with a soft fur called the lanugo coat.
■ Pups are born one at a time, and reports of multiple births (twins or more) are rare.
The First Weeks
■ Pups will nurse for three to six weeks, but that depends on how safe conditions are. During that time, the pup may be left alone for a few hours while the mother forages. As the pup ages, the mother will spend more and more time out foraging to keep up her strength.
■ Pups shed the lanugo coat shortly after birth and the juvenile coat underneath remains.
■ Once weaned, the pup is no longer dependent on its mother and the bond dissolves. Juveniles forge for their own food.
■ After they molt as juveniles, their adult coat grows in, which they have the rest of their lives. Their coats have clinal variance, which means they have lighter coats with darker spots in San Diego, and going north up the coast, seal coats get darker and the spots get lighter.
■ There is no obvious way to differentiate between males and females, they are approximately the same size and have the similar coats. Only a mother nursing her pup or an up-close inspection would tell.
■ Fathers have no roles in a seal pup’s life, and neither do mothers after the pups are weaned. There is no family structure or herd of any form once the pups are weaned. The mother’s only role is to strengthen the pup enough so it is ready to wean within six weeks. The mother’s milk has a high-fat content and is so nutrient-rich that pups are strong enough and grow enough to forage on their own within two months. “They don’t need each other after that,” DeAngelis said.
■ Pup mortality rates vary based on environment, breeding conditions, presence of food, presence of Domoic Acid (a naturally occurring toxin in the ocean) and also, who is counting. Another factor is whether the pup nursed long enough to survive on its own.
■ Reports range from a 20 percent mortality rate to the occasional year when there is 50 percent pup mortality.
■ A healthy male seal can live to be 25 years, a healthy female seal can live to be 35.
■ Depending on conditions, a female seal will give birth once a year to once every three years. Many Light readers commented on the perceived increase in the seal population at the Children’s Pool. A big part of that is due to the implementation of the 1972 Marine Mammal Protection Act (MMPA), amended in 1994 to include pinniped-fisheries interactions and further define harassment.
Prior to then, there was a hunting bounty on seals and sea lions and the population was devastated. Since then, the population has been gradually increasing both in Southern California and the other five recognized stocks (areas where seals live and give birth).
The stocks are found in Alaska, the East Coast, Southern California, Washington/Oregon and one in Europe. DeAngelis estimates between 26,000 to 27,000 seals are found in Southern California, and she could only guess at how many worldwide.
■ Population is also affected by the presence of food, however it is also known that harbor seals do not have discriminating taste and will eat what is available.
■ The pinniped dines on what is available in the area. In La Jolla, seals eat small fish, octopus and squid. DeAngelis noted in Alaska, seals have been seen hunting for slow moving shrimp.
■ One catch to this diet is that Domoic Acid bio-accumulates in the fish. While found in small amounts naturally in the small fish, the more fish they eat, the more they ingest.
■ Harbor seals eat 5-6 percent of their body weight per day.
— UP NEXT: In the next installment of this series coming in the March 28, 2013 issue, learn how Domoic Acid impacts Harbor Seals as well as other ailments that affect them; how they’ve acclimated to humans; and their mating, pregnancy and birthing rituals.
— NEXT STORY: See Part 2 of The Seal Deal series at http://www.lajollalight.com/?p=104373
MORE FACTS: SEAL SCIENCE
■ Seals insulate themselves using a thick fur coat and layer of blubber. In polar environments, seals restrict blood flow to their skin surface to keep from releasing internal body heat to the ice. In warm environments, the reverse is true. Blood is sent toward the extremities, allowing heat to release into the environment and letting the seal cool its internal temperature.
■ Seals have several natural predators. These include sharks, orcas (killer whales) and polar bears.
■ Humans are the greatest threats to seals. Seals have long been commercially hunted for their pelts, meat and blubber. The Caribbean monk seal was hunted to extinction, with the last record reported in 1952. Today, all pinnipeds in the United States are protected by the Marine Mammal Protection Act and there are several species protected under the Endangered Species Act (e.g., Steller Sea Lion, Hawaiian Monk Seal.) Other human threats to seals include pollution, oil spills, industrial pollutants and competition for prey with humans.
■ Seals detect prey with their whiskers. The seal sweeps its upper lip to and fro, using its whiskers to detect fish in murky waters.
■ Seals have large, round eyes that are able to focus both above and below water.
■ Seals are able to hold their breath for a long time during dives, using oxygen stored in the blood and muscles as well as the lungs.
■ Seals can sleep underwater. They can even surface to breathe without awakening.
— Sources: sealsworld.com, wikipedia
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