Hunting in the Antarctic, taking a break in the tropics
Visiting the Orcas
An Antarctic orca spy-hopping dinner for the family. Photo by Robert Pitman
Thursday evening: The largest populations of orcas in the world aren’t here off the coast of North America; they’re in the Antarctic.
We all gathered for dinner again at Candace’s home for an evening that included a presentation about the Antarctic orcas and a preview of the new movie The Whale.
Ecologist John Durbin has spent time with orcas in the Southern Ocean, studying the various subspecies along with the cultures and hunting practices of each of the different groups.
John explained that killer whales off of the western Antarctic Peninsula are very fussy diners. They’re renowned not just for their cooperative strategies and hunting tactics in catching Weddell seals, but also for the fact that they will barely ever eat anything else but this particular species of seal. They do like a few other treats like breast of penguin. But they won’t eat any other part of the penguin. And when you bear in mind that they don’t have hands or paws, eating only very precise parts of an animal takes some skill in itself.
John and his colleagues learned all this by making careful observations during the Antarctic summer of 2009. They discovered how the orcas avoid almost all other animals who would be easy catches, including other kinds of seals, in favor of what are for them the more yummy Weddell species.
The team documented how the orcas work together to snag their prey. They start by scouting out their victims in what’s called spy-hopping — surfacing for a quick reconnaissance to spot Weddell seals resting on ice floes.
The orcas set up a wave to tip the seal off the ice floe
Then, rather than killing the seal directly, members of the pack will pull her underwater repeatedly by her hind flippers, until she’s too exhausted to swim. After the kill, the orcas work together to ensure that the carcass is divvied up properly amongst pod members under the waves.
You can see in this video how the orcas line up together (including with their calves to teach them how it all works) and then create a very precise wave that will lift one side of the ice floe where the seal is resting, and so tip her into the water.
At least once a year, the orcas take a break from the icy waters of the Antarctic and head up the coast of South America to the tropics for their equivalent of a spa treatment. They won’t eat while they’re away, and it’s a long trip — more than a thousand miles each way. And the reason they go is in order to be somewhere nice and warm where they can slough off the top layers of their skin, which have become tough and discolored. Doing this in the frigid waters of the Antarctic would not be a fun experience, so it’s worth the long trip.
There’s so much to be learned about these animals whom John refers to not simply as top predators, but rather “top top predators.” There’s simply nothing on the planet that can touch them.
Except, of course, for humans.