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Posts Tagged ‘Northern elephant seal’

Amazing footage!

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In both northern and southern elephant seals, only a few males produce offspring ever year. The bulls lay claim to a stretch of beach and then claim as many cows as possible.

And yes, it really must suck to be a cow elephant seal.  During this time of her life, she continually being herded by males much larger than she is. And never mind the mechanics of their reproduction. She is a large seal, but she is significantly smaller than the male.

If you’re an elephant seal bull, you must be big and nasty if you are to reproduce. Only one in ten males manages to reproduce. That is an astoundingly low number:

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These selective pressures on the elephant seal species have resulted in a favoring of bull seals that are the equivalent of the most-used sire effect in many breeds of purebred dog.

The northern elephant seal nearly went extinct. Its population may have dropped to only 100 individuals. Today, there are 100,000 northern elephant seals, and because of their particular breeding arrangement, very few males pass on their genes every generation.

It is very similar to what has happened in many purebred dogs, and I’m sure that some will suggest that if the northern elephant seals are able to have a healthy population, then it should be okay to breed dogs in this fashion.

The problem with that logic is that we actually don’t know the full consequences of the extreme genetic bottleneck on the northern elephant seal. Because they lack genetic variation, it is possible that an epidemic or even a slight environmental change could prove disastrous for the seals.  In normal populations, genetic diversity means that some animals will have some resistance to potential changes in the environment or infectious disease. However, if all the seals are genetically quite similar, they may all be similarly susceptible to these problems, which means they could all die off.

Again, the fact that it hasn’t happened yet doesn’t mean that it can’t.

The other thing is elephant seals are under the pressures of natural selection. Dogs really aren’t. Really defective seals don’t live very long. They wind up in the bellies of orcas or great whites. Truly defective elephant seals don’t reproduce. With dogs, we can continue to select for defect, intentionally or unintentionally. We can select for a whole range of disorders and not even know it until a third the dogs in any given breed have them.  (That is only slight hyperbole.)

One of the delusions we have is that we think we can just selectively breed out disease without actually realizing that we’re dealing with a dynamic genome.  I’m not in favor of breeding dogs with disease. Don’t get me wrong.

But unless we look at the whole system that leads to an accumulation of these diseases, we are doomed to failure. It is quite literally little more than rearranging deck chairs on the Titanic to think we can just cull for this disease or that one and not realize that the problem is much more systemic than peculiar.

Nature has done what it can to save northern elephant seals. Considering how these animals breed, I would certainly have wanted to have started with a larger founding population than 100 to 1,000 individuals.

But we didn’t get that choice.

With dogs, we have that opportunity, but it remains denied to us, simply because we cannot change our thinking.

As I’ve said before, the human ego is probably the most destructive part of the relationship between man and dog.

We are the so-called rational species, and in this relationship, we’re supposed to be the responsible ones.

But for all of our intelligence, we have failed our dogs.

And it’s something we need to think about.

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It’s a Northern elephant seal skull.

This is what they look like alive:

Source.

Northern elephant seals are the second largest members of the order Carnivora. The largest is the Southern elephant seal.

This may have been a bit confusing for some of you because seals, sea lions, and walruses were once classified in their own order called Pinnipedia. This order is no longer considered valid.

Seals, sea lions, and the walrus are derived from the same common ancestor as bears.

That puts these marine mammals with in the suborder Caniformia. This suborder includes dogs, bears,  the red panda, mustelids, skunks and stink badgers, and procyonids.

The smallest member of the order Carnivora is the least weasel. It is a mustelid, and it is also a member of the suborder Caniformia. The largest fully terrestrial member of the order Carnivora is the Kodiak subspecies of the brown bear, but the largest bear is the polar bear, which could be classified as a marine mammal.

The other suborder in Carnivora is Feliformia, which isn’t quite as spectacularly diverse in shapes, but it does include hyenas, which is why hyenas are more closely related to cats than they are to dogs.

I should point out that Southern elephant seals are significantly larger than Northern elephant seals. The biggest bull Northern elephant seals weigh about 5,000 pounds. On average, the biggest Southern elephant seals weigh over 8,000 pounds. The biggest on record was nearly 11,000 pounds in weight.

In case you’re curious, the walrus is a close third behind the northern elephant seal when it comes to size. The biggest bull walruses weigh over 4,00o pounds.  The fourth largest is the Steller’s sea lion, which gets up to around 2,500 pounds.

All of these are much larger than Kodiak and polar bears. The biggest wild Kodiak bears weigh over 1,400 pounds, and the heaviest polar bear on record supposedly weighed over 2,000 pounds (I’m skeptical). One should remember that polar bears are actually a modified brown bear that can utilize marine and polar ice environments.

Northern elephant seals experienced a rapid population drop when whalers augmented their stores of train with their blubber. The population is believed to have dropped to as low as 100 individuals. There are currently 100,000 of  them on the Pacific Coast of North America. These animals have very low genetic diversity, and although they appear fine right now in terms of their productivity, the species could be fragile.

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Actually, especially if it’s  in the water!

The diver who got attacked said “It looked friendly.”

Um.

I’m not expert in elephant seal body language, but if I saw a dog with that expression on its face, I don’t think I’d be petting it!

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All Northern elephant seals have the same male ancestor.

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.

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