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July 28, 2003

More whales-it's in the genes

One thing I always find sketchy about ecology are the population estimates for various species which can't be tracked easily (under the sea, in the forests, etc.). In the end, I agree that there have be some aproximations, and they might be the best numbers we can come up with at any given time, but when those numbers are brandished in public policy discussions as definitive and established I get a bit nervous. In any case, I found this news reported in Scientific American very interesting, because it indicates that past estimates of baleen whale populations (on the order of 50,000 or so) prior to their decimation might be wrong, insofar as they do not suffice to account for the genetic diversity found in present whale populations. In fact, the estimates of wild whale populations prior to the 19th & 20th century drives toward extinction might be off by an order of magnitude, think 500,000 rather than 50,000. Still, this is an estimate, but genes have no great reason to lie or be biased in any way. Of course the best solution is to come to the same number from various vantage points. Finally, I am a bit curious as to possible ramifications this might have on our conception of the marine ecology as a whole, as some ecologists assert that penguins and other krill consuming species have benifited from the decline in whale populations. An examination of penguin DNA should indicate a rapid population expansion in the recent past. One implication of this sort of thinking is that the ecosystem has perhaps requilibrated (a higher portion of the biomass being penguins rather than baleen whales) and humpbacks and their cousins have too much avian competition to reach their old numbers again.
Here are more stories on this issue (not much more red meat than what you'd find in Scientific American though).

Posted by razib at 06:29 PM

genes have no great reason to lie or be biased in any way

And the Whaling captains of the 19th century, who scoured the World's oceans in search or their quarry, were so incompetent that they didn't have a clue of the whereabouts of over 90% of the Whales, using methods that were, however, sufficiently effective to almost wipe the Whales off the face of the Earth.

The genes may not lie, but researchers are human, and therefore do. I may not be a geneticist, but in statistics we would throw away the outliers. In other words, a new study that produces results that are so far away from anything preiously known is, at best, a curiousity, that probably is about an order of magnitude out of whack. It is not a reason for us to now believe that it was the Penguins who wiped the Whales off the face of the Earth.

Posted by: Michael Gersh at July 28, 2003 07:24 PM

Do penguins and whales really compete that much for food? Penguins can't hunt so far nor so deep as whales, even if they eat the same critters. Nor do krill migrate vast distances.

Anyway, genetic evidence of a population crash doesn't mean we caused it. Maybe whales were more numerous 10,000 years ago for other reasons.

Another possibility though is that early whalers caused a population crash via some poorly understood mechanism (interfering with whale breeding?) before the whale counts became more accurate.

Posted by: bbartlog at July 29, 2003 09:34 AM

ain't no penguins engaged in battles to the death with giant squids in the blackest depths...whales rule.

Posted by: sliggy at July 29, 2003 09:42 AM

10,000 years ago doesn't cut it. The point of the exercise is to stop commercial whaling, which depends upon a comparison of whale populations as they existed 150 years ago. I agree that, back in the day when whales might have still been land animals they might well have been much more numerous. That does not bear upon the attempt to create a controversy that will stop the slaughter of whales today, and the fact that Scientific American has become a source of politically driven junk science. It is really too bad, as it used to be such a fine publication.

Posted by: Michael Gersh at July 29, 2003 11:24 AM