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.