By Ashley Mackin
In the second of at least three parts in our seal series,
La Jolla Light
continues its expose on the pinnipeds (fin-footed mammals) at La Jolla's Children's Pool with the help from marine biologist Monica DeAngelis of the National Oceanic and Atmospheric Administration (NOAA) Federal Advisory Committee.
In the second installment, DeAngelis answers questions about seal mating and pregnancy, as well as the illnesses they are subject to and how they’ve acclimated to humans.
Mating and Pregnancy
■ A seal will return to the site where it was born to give birth. Therefore, DeAngelis said the seals born at Children’s Pool would likely return there to give birth, making them more residents than visitors.
■ Because mating happens in water, very little is known about the courting habits of harbor seals. Scientists have observed tail flapping and attention-getting attempts during mating season.
■ Males typically only produce one pup per season, and males rarely produce more than one. “That male could have attempted to mate with 10 different females, but the (genetic) result of that encounter was one pup with one female,” DeAngelis said, “The action may have been there, but no result.”
■ Additionally, females can delay the implantation of a fertilized egg to ensure they give birth during pupping season. She will carry the fertilized egg for one to three months before she is officially pregnant.
Taking delayed implantation into account, a seal’s pregnancy lasts 9–11 months. (One theory of why males can only reproduce with one female per year is that she may already be carrying a fertilized egg that has not been implanted.)
■ Seals reach sexual maturity at 4-6 years old. They often give birth on land or some land-based object. However, because newborns can swim right away, seals can give birth in water. DeAngelis said she thinks the frequency of births in water is very low.
■ Because a seal’s sexual organs are internal, it is impossible to tell males from the females without an upclose inspection, which DeAngelis does not recommend. A nursing mother is one clue.
Illness, Seal bites
■ The presence of Domoic Acid, a naturally occurring neurotoxin in the ocean that bio-accumulates in seals prey, makes them susceptible to seizures.
■ Seals are also subject to Phocine Distemper Virus, which also affects dogs. The Distemper Virus can kill.
■ A seal’s most common problem is a viral and/or bacterial infection, along with parasites that attack the heart, lungs, skin, nasal cavity and blood vessels.
■ In the event a seal bites a human, the bacterial infection could spread to the human. DeAngelis said as with any wild animal bite, it needs to be cleaned and treated or the victim could lose the area around where they were bit or the infection could become systemic. DeAngelis warns, though seals seem to be used to humans, they are still wild animals and can bite.
■ Seals bite if they feel threatened or if their pup is threatened. Seals might also be more defensive if they feel sick. Seals at Children’s Pool are so acclimated to humans, they are less likely to bite, DeAngelis said.
■ Mortality rates are higher for newborns than for adults, who could live to age 35.
Seals and Humans
■ Living in an international tourist center like the Children’s Pool in La Jolla exposes the seals to humans. They are similarly exposed at a haul-out site in Carpinteria in Santa Barbara. “At this point, I would call (La Jolla’s seals) urban wildlife because of the conditions they are used to living in now,” DeAngelis said.
■ The human interaction factor extends further when humans take pups home with them, thinking the pups are abandoned. DeAngelis said they have received reports of people keeping them in the bathtub, something she does not recommend.
“(People) take a pup home and then poor mom seal comes back from her foraging trip and her pup is gone,” she said, adding that a mother might be gone for a few hours to a few days, depending on the age of the pup.
“That’s why we have guidance in place; the public can call in if they see what they think is an abandoned seal,” she said. “What we do is put a watch on it to see if it indeed had been abandoned, if it is all alone or acting strangely, losing weight or if it’s been abandoned for a few days.”
Influencing Seal Behavior
The seals at Children’s Pool, now quite used to humans, are not easily influenced by human behavior. At the Carpinteria haul-out site, however, there was a behavior shift where seals took to hauling-out mostly at night when there were fewer humans around.
“I wouldn’t say that they were trained to change their behavior; I think it’s just a response to the threat that humans potentially posed in that area,” DeAngelis said. “They didn’t abandon the site at all, they just shifted their haul-out pattern and in different places on the beach.”
Up Next: In the April 4 issue, the community of seals at Children’s Pool, specifically, will be addressed. We will look at the legality of moving them, how they’ve impacted the environment, and how their environment has impacted them.
■ If a seal gets sick or is confirmed abandoned, volunteers and staff from SeaWorld San Diego will come to rescue them. SeaWorld is not paid by NOAA for its services. Rescue Hotline: 1 (800) 541-7325.
■ David Koontz of SeaWorld addressed the rumor that the seal population at Children’s Pool has increased because SeaWorld releases rehabilitated pups in La Jolla. “We rescue, on average, less than 10 harbor seals annually,” Koontz said. “They are released in ocean areas where others of their kind are already and there is a known food source.
■ “Harbor seals are often found foraging in the kelp beds that are a mile or two off shore. We return this species to the ocean on the west side of the kelp beds. There is not only a good food source for the harbor seals present in the kelp beds, but the kelp beds also provide a degree of protection from other predators. We don’t return harbor seals at the Children’s Pool.”
What is a Haul-out?
■ Hauling-out is the behavior associated with pinnipeds of temporarily leaving the water between periods of foraging activity for sites on land or ice. A distinction is made between reproductive aggregations, termed “rookeries,” and non- reproductive aggregations, termed “haul-outs.”
■ Other benefits of hauling-out may include predator avoidance, thermal regulation, social activity, parasite reduction and rest. — Wikipedia
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The Seal Deal