From the BBC’s Planet Earth series:
This is pretty famous footage, but I noticed in the sequence something that is worth exploring from evolutionary perspective.
Notice that when the fur seal catches the penguin, it uses a vigorous shaking motion to complete the dispatch.
It doesn’t kill the penguin quickly. In fact, the seal had tried to rip out its throat, that would be a much quicker way to kill the prey.
However, its very likely that the seal cannot make a choice as to the best way to kill the penguin.
Its killing motor pattern is likely inherited, and anyone who has a dog can recognize the sequence. Give a dog a toy to play with, and they very often exhibit a vigorous shaking pattern as they play with the object.
It’s a motor pattern that has to be trained out of most retrievers, but as a type, they tend to exhibit this motor pattern less often than other dogs, though there is quite a bit of variation within individuals.
In my short time with Pavel, the West Siberian laika, I noticed that his shaking motor pattern was quite vigorous compared to Miley’s. That’s because Pavel’s ancestors have never really been expected to bring prey to hand alive, while Miley’s certainly were. Indeed, Pavel’s ancestors had to kill sable and other fur-bearers and fight off bears and wolverines. Miley’s most immediate ancestors came from genteel shooting estates from Great Britain, where the biggest predatory mammal is the Eurasian badger.
This motor pattern is instinctive in dogs. It does serve a purpose whenever one sees a dog catch a smaller mammal or a bird. A few vigorous shakes usually breaks the neck of the quarry, and it then can be eaten.
This same motor pattern also exists in bears, and when one reads of a grizzly bear attack, the victims often experience violent shaking in the bear’s jaws.
Because this behavior exists in dogs and bears, one can see why the Antarctic fur seals engage in it.
Within Carnivora, there are two major suborders– Feliformia and Caniformia. Bears, dogs, and seals (including true seals, the walrus, and the fur seal and seal lion family) form a clade.
That means they all share a common ancestor about 40 million years ago.
At that time, the dog and bear lineages diverged.
And then about 23 million years ago, the bear and seal, sea lion and fur seal, and walrus lineages diverged. Bears as we know them now didn’t evolve until about 20 million years ago, and the ancestor of the seals and other marine Carnivorans was actually something like an otter.
Fur seals are actually sea lion species, and Antarctic fur seals live almost exclusively on krill. They’ve likely been living on krill for thousands of years, and their ancestors have been living a marine existence for millions of years.
If this shaking motor pattern in Antarctic fur seals is inherited, as I think it likely is, then dog breeders who want to breed it out might have a task on their hands.
For thousands and thousands of generations, these seals have not needed this shaking behavior in order to survive, but when they engage in something similar to the predation of their terrestrial ancestors, they engage it.
I would like to see some comparative studies of this shaking motor pattern in different fur seal and sea lion population in order to see if this behavior actually is inherited.
But if it is, it is a wonderful example of an historical legacy.
A wonderful little piece of evidence for evolution.