Natural History

All Northern elephant seals have the same male ancestor.

Northern elephant seals can be found in the Pacific from Alaska to Mexico. However, their main breeding beaches are on the coasts and islands of Baja California and the US state of California.

Whalers killed the seals for augment train oil loads. The seals have a thick layer of blubber, which can be boiled down to train just as easily as anything marine mammal.

The animals disappeared from US waters by the beginning of the twentieth century. The only known rookery for these seals that remained was the remote island of Guadelupe, which you might know  from Shark Week documentaries as home to many Great Whites.

The whole population may have dropped to as low as  50-100 individuals. This is a low number when you consider how these seals breed.

The cow seals come ashore first, where they give birth to their pups, which they have been carrying for for seven months. The full gestation of the elephant seal is roughly 11 months, but the embryos don’t implant until four months after mating.

The cows nurse their pups for about 24 days. By then the males have come to shore. It is at this time that the males claim sections of the beach through what are perhaps the most impressive fights in any species of marine animal. Just a few males get to claim the sections of the beach.

And those males breed the females. If you would like to see how large elephant seal harems are, check this video with Sir David Attenborough. (These are Southern elephant seals, which are bigger.)

This is really similar to the most-used sire phenomenon in purebred dogs.  However,  this was a natural breeding situation that was made worse through over-exploitation of the animals.

The seals have very low genetic diversity, which could mean that they are quite vulnerable. Genetic diversity gives wild animals a chance to survive epidemics and environmental changes. Within a diverse population, there will be animals that have some resistance to these factors, and these animals will be survive. They will pass these genes onto their offspring, and the species is saved.

If you have narrow gene pools, though, you have a population that may not have those resistant individuals, and if something bad happens, it could wipe them all out.

This same thing could happen to our livestock, especially poultry, which are all heavily inbred. We need to think about genetic diversity in our domestic stock.

So let’s hope the elephant seals don’t become suffer any severe challenges to their existence.