Notes from a talk by Bob Pitman on Antarctic orcas, Nov. 18, 2009 – hosted by ACS Puget Sound
The classroom at the Phinney Neighborhood Center in Seattle was filled wall to wall with people eager to hear about the four (3 for sure, 1 probable) types of orcas he’s found that stalk and forage in and around the ice floes and pack ice (there’s a difference) in Antarctica. I don’t think anyone was disappointed. The entire hour-long presentation was non-stop with amazing stories and discoveries, vivid observations and some incredible images of divergent cultures of orcas at work and play.
It was like watching a lecture by a 19th century anthropologist just back from a scientific expedition deep in the Amazon jungle, enthralling the audience with incredible tales of outlandish natives and their curious customs. That’s how exotic these A, B, C and, possibly, D orca types are, and how startling are the discoveries over the past several years by Pitman, his colleague John Durban and their team in the bright, cold Antarctic summer.
Caveat: These notes are by no means comprehensive, and I invite anyone else who was there or has anything to add, to do so.
Beginning in 2000 Pitman has conducted field studies on Antarctic orcas, and has consistently proposed multiple species, or at least “ecotypes” occuring sympatrically (found in the same habitat). Some of his published works include:
LeDuc, Richard G., Kelly M. Robertson, and Robert L. Pitman (2008). Mitochondrial sequence divergence among Antarctic killer whale ecotypes is consistent with multiple species Biol. Lett. (2008) 4, 426–429.
Pitman, Robert L., Wayne L. Perryman, Don Leroi, and Erik Eilers (2007) A dwarf form of killer whale in Antarctica Journal of Mammalogy, 88(1):43–48
Pitman, Robert L. Good whale hunting: two tantalizing Russian reports take the author on a quest to the Antarctic, in search of two previously unrecognized kinds of killer whale Natural History, December 2003.
To set the stage for this travelogue to Antarctica, Pitman first described the different ecotypes (orcatypes?) documented in the Pacific NW to establish his frame of reference, because our familiar residents, transients and offshores were the first to be researched in the mid-1970s and remain the best known orcas in the world. He said mammal-eating transients are probably a different species than fish-eating residents and that we should look for a paper he will co-author to describe the transient species soon. He also tantalizingly mentioned that there may be up to five species of orcas worldwide.
In Mitochondrial sequence divergence among Antarctic killer whale ecotypes is consistent with multiple species, Pitman writes:
“Type A has the typical black and white coloration; it inhabits ice-free waters and appears to prey mainly on cetaceans, particularly Antarctic minke whales. Type B is grey, black and white, with a larger eyepatch and a distinct dorsal cape; it forages in pack ice and feeds on pinnipeds. Type C is similar to type B in appearance but with a narrow, oblique eyepatch; it is most frequently encountered in dense pack ice where it specializes on fishes.”
That dorsal cape on Types B and C would be the envy of any hot rod pin-striper, sweeping along the upper torso starting in front of the blowhole and arcing into the saddle patch (see Uko Gorter’s detailed illustrations in the same paper). Besides this striking coloration in Types B and C, the body size differences are substantial: Type C males average only 18.3 feet, with the largest male at 20 feet. Type A males average nearly 24 feet, and the largest was 29.5 feet, 50% larger than Type C. Type B is smaller than Type A but larger than Type C.
But it’s the degree of dietary specialization by each type that is most astounding. Type C, for instance, feeds almost exclusively on toothfish, which can exceed 440 pounds, and reach a length up to 7.5 feet, though most are less than half that size. Unfortunately legal and illegal fisheries target toothfish, reducing their numbers each year, and according to The Antarctica Project, “It is common practice in the illegal fishery to dynamite Sperm and Killer whales when they are discovered in the area where the fishing takes place.”
The incredible forethought and teamwork shown by Type B as they take down Weddell seals was the subject of most of the presentation. They feast almost exclusively on Weddell seals, while completely ignoring leopard seals and crabeater seals, both very abundant in the same waters.
Pitman recounted some amazing stories of careful planning and execution as Type B orcas captured, drowned and devoured the seals. Numerous photos and descriptions showed Type B orcas seeking Weddell seals by spyhopping repeatedly en masse around the ice, then rushing at the floes abreast to toss a wave over the flat ice, either washing the seal off the ice or breaking up the ice until not enough is left to keep the seal safe from the orcas’ toothy grasp. The middle of the wave often peaked in a frothy breaker aimed directly at the seal. On several occasions crabeater seals were washed off ice floes, then left alone when the mistaken identity was realized. In at least one instance, the whales neatly skinned a seal with incisions along the neck and midsection, then the skin was pulled off the carcass by at least two orcas. Pitman also documented Type B orcas taking an elephant seal and a minke, but never a leopard seal or crabeater seal.
The audience was then treated to lengthy discussion and photos of yet another type, even more bizarre than the others, which Pitman calls “Type D,” which have large bodies, tiny, slanted eyepatches and bulbous heads, and are the least documented. Pitman was tentative about naming them as another type, but he has amassed a collection of photos and field reports about them in just the past few years. Satellite tags have recorded Type D traveling 150 nautical miles per day for ten days. It’s usually said that orcas can travel up to 100 miles a day, but apparently that will now have to be revised upward. In the Q&A, Pitman clarified that no fighting was seen among any of the orca types; and that they always share food.
Last season and this season’s fieldwork is conducted partly in cooperation with a BBC crew filming a special to be called: “Frozen Planet” which will effectively announce these incredible orca types to the wider public. I know I’ll be watching for it.
I went away curious about the taxonomic thicket that might ensue when transient orcas are proposed as a separate species. I wonder how far that might go, since theoretically every genetically distinct orca community could then be considered a separate species. Is it possible that the paradigm and taxonomy from biology are insufficient to describe the “ecotypes” that are found around the world? If Rendell and Whitehead are right in Culture in Whales and Dolphins, orcas have independently evolved cultural capabilities without parallel except in humans. Would designating mammal-eaters and fish-eaters as separate species be analogous to describing isolated human societies as separate species? In some cases interbreeding may have become impossible, but for most combinations of sympatric communities it’s possible, but virtually never done.
In discussions of orcas, and possibly sperm whales, humpbacks, pilot whales, and others, might cetology find it useful to borrow some of the concepts and terminology from anthropology and sociology? I wonder if the various orca types and communities could be described as “cultures” rather than “ecotypes” for instance? Just wonderin.’
Thanks so much for this account, Howie. I was really sorry to not be able to make the talk!
I think it is timely to begin trying to talk about social evolution in killer whales. I’d support the notion that orca behavior could be broken down into memes. In fact, in Beam Reach research we already categorize southern resident behavior into distinguishable units.
An ecotype implies genetic difference, but not so much that interbreeding would affect fitness. I bet one could argue that the northern and southern residents have greater memetic than genetic differences. Indeed, the listing of the southern residents as a distinct population segment (DPS) hinged primarily on behavioral or cultural (I’d choose “memetic”) differences, not genetic or taxonomic (morphological) ones. The implication is that their vocal, social, and foraging behaviors are unique and would not be replaced were the Salish Sea niche available the offshore, transient, or northern resident populations.
As we use passive and active acoustics to understand the underwater behavior of southern residents, we must think hard about how their particular behaviors may be the product of natural selection and impacted by anthropogenic pressures. I meme it!