Always ethereal, always eclectic, I write as the mood strikes, when there intrigue reveals itself. Usually that means something controversial or adventure of some sort.

I've tried really hard to be unprovocative, but have as yet been unsuccessful.

Sunday, 25 March 2007

More Wet Stuff

A very full weekend. I love it- free marine biology instruction, in prep for our volunteering. But so much all at one time, without a traditional weekend break. I'm really feeling not being able to go to Meeting this past Sunday (and now two weeks in a row). But there are certainly moments of pure joy- such as learning on my way to the training session that the Seattle Pigs are back!

Sunday was another five hours of instruction, this time focused on the one's with backbones, fish and mammals. Learned some rather interesting items about both. There is a long term six-gill shark study going on below the Seattle Aquarium pier, suspended at the moment because of issues with the new pilings they put in, but due to restart this July. We got to watch some excellent video of the study, where they are monitoring and shark movements and tagging with audio and visual markers, by putting chum into the water below the pier. Sadly these are only mid-range sharks, of 7-10 feet. The study controllers are fairly confident that this is not habituating shark habits, as the acoustic tags indicate the sharks regularly swim by. But the study may be teaching them that food is available every month at the aquarium pier, when the chum is released, indicating an ability to learn in the sharks. The speaker shared that, even down 45 foot, rapture of the deep sets in, and when a shark can't be reached with a tag, the divers want to go out of the cage to put it on the shark while it's feeding. This is why all decisions of this sort are made on the surface, by someone not at all effected by nitrogen narcosis.

For me the highlight of the day was the first half, focused on the Orca, where we learned about the local population of some 86 individuals. I was shocked at how small our population is in this area, as I thought it was in the thousands. Evidently, until they started monitoring Orca, that was widely thought to be true by most scientists. It was only after some 50 Orca from our local population were taken for SeaLife Parks that they realized an entire generation had been removed, decimating the local population. To be clear- if you go to SeaWorld and most SeaLife Parks in the U.S., we benefit from the near destruction of the local Orca population here.

That is in part because they are consummate K-strategists, with long gestation periods and not reaching sexual maturity until 9-12 years of age. I was completely taken aback to learn how long Orcas can live. One particular Orca male in the local population, Ruffles, known by his wavy fin, is around 45. He follows after the matriarch of his pod, J-Pod. She's Granny, and is 90 years old now.

Orcas, I learned, are not endangered world-wide, but they are in the local population. There are distinct differences between different Orca populations. The Antarctic population has three different variates, as does the local Puget Sound population- and those two groups of three are distinct from each other as well. The local population has the fish-eating Residents, the pinniped eating Transients, and the big-fish eating Offshore group. These groups are so distinct that a seal will not respond at all to a Resident, but if it notices the silent approach of the hunting Transient it hightails it out of there. (See swimming Orca-cam here.) There is such a great degree of difference between the three groups, not having interbred for at least 100,000 years, that there is a move by some to place them in separate subspecies or even species. What we are observing here is a Mammalian speciation event!

What keeps the groups apart, when they are all capable of interbreeding (presumably) and live in the same area? Evidently, culture. While there are some minor differences morphologically, so that if you look close you can tell the difference in dorsal fins between Residents and Transients, their preferred food has profound implication in who they hang out with. Transients don't go after just Pinnipeds, but also sick adult whales and calves. They are the ones with the fearsome nature that earned Orcas the false moniker of "killer whales".

In the Puget Sound area there was actually a near attack by a Transient. We heard about a boy playing in the water, and his grandmother on the beach saw the a gigantic wave and high fin rushing at full speed towards the boy. The grandmother let out a scream just as the whale came up to the boy, realized he wasn't a seal, did an abrupt bypass of the boy, knocking him over, and returned to the sea. Right afterward video was taken of a whole pod of the Orca in deeper water near the beach engaging in percussive behavior, slapping their pects on the water in what what may be a form of communication. I like to think they were saying, "So sorry- thought you were a seal." There has never been a confirmed attack by an Orca, Transient or otherwise, on a human (in the wild).

But there have been plenty of such on other Orca, particularly on the Resident population. One might think that therefore this keeps the two groups from interbreeding, as the Residents avoid the more fearsome Transients. Surprisingly, as the Resident pods are much larger, it is the other way around. And so there has been 100,000 years of no breeding because the Transients, as soon as they see Residents in the water, will turn and run the other way.

Therefore, because there are so many distinct subgroups of Orca, in this area a great amount of their genetic distinctiveness is endangered. Add that in to the significant amount of PCP's in the Orca milk, from so many decades of it's use, and you have a very endangered population indeed.

1 comment:

CV Rick said...

It's quite coincidental that I read this in your blog (which I just found, by the way). I watched a fascinating video account of a group of Orcas attacking and drowning a California Grey Whale and her calf.

I have learned more about Orcas over the past week than I ever knew before. Thanks.