Posted by: Dan | September 15, 2007

Squid Migration Drove Whale Sonar Evolution

This came out over a week ago, and has been sitting around among my bookmarks – I couldn’t ignore it forever though. As reported on ScienceDaily, Migrating Squid Drove Evolution Of Sonar In Whales And Dolphins, Researchers Argue.

Lindberg, a specialist in the evolution of marine mollusks, noted that cephalopods have migrated up and down on a daily “diel” cycle for at least 150 million years. At the time whales developed biosonar, nautiloids dominated the oceans. Lindberg and Pyenson propose that whales first found it possible to track these hard-shelled creatures in surface waters at night by bouncing sounds off of them, an advantage over whales that relied only on moonlight or starlight.

This would have enabled whales to follow the cephalopods as they migrated downwards into the darkness during the day. Today, the largest number of squid hang out during the day at about 500 meters below the surface, though some go twice as deep. During the night, however, nearly half the squid are within 150 meters of the surface.

Over the millennia, cephalopod species in general – and especially shelled cephalopod species – fell as the number of whale species boomed, possibly because of predation by whales. Then, about 10 million years ago, the whales seem to have driven the nautiloids out of the open ocean into protected reefs. Lindberg said that the decline in nautiloid diversity would have forced whales to perfect their sonar to hunt soft-bodied, migrating squid, such as the Teuthida, which in the open ocean are typically two feet long or bigger and range up to the 40-foot-long giant squid.

So you see, migration was an effective strategy, until cetaceans joined in with their own sonar ‘arms race.’ Nifty.

About these ads

Responses

  1. Interesting how that “150 million years” figure is taken for granted, especially since carbon-14 dating is only at it’s most accurate when measuring items going back 3500 years or so. The farther you get away from that time period, the more inaccurate the method becomes, to the point where it’s completely unreliable for fixing dates older than 10,000 years. If anybody knows what method Lindberg, et al used to get that figure, please enlighten me.

    Also, since the rest of the article is supposition, it amounts to an atheistic game of make-believe, with no scientific proof. Very similar to Darwinian Evolutionary Theory, that.

  2. 1. Lindberg et al. didn’t use carbon-14. They did cite studies that used radiometric dating however – studies which didn’t use carbon-14 either. They used rubidium/strontium, thorium/lead, potassium/argon, argon/argon, and/or uranium/lead, all of which have very long half-lives, ranging from 0.7 to 48.6 billion years.

    2. Lindberg and coauthors wrote in their paper:

    Here we propose that the origin of echolocation in odontocetes was initially an adaptation for nocturnal epipelagic feeding – primarily on diel migrating cephalopods. We test this hypothesis using data on the temporal, geographical, and water column distributions of odontocetes and cephalopods, and other global events from their respective tertiary histories.

    That is, the data that they looked at was the distribution of toothed whales and cephalopods to make some basic inferences.

    3. Paleontology as a means for reconstructing ethology does have its problems. But “an atheistic game of make-believe”?? That doesn’t even make sense.


Categories

Follow

Get every new post delivered to your Inbox.

Join 54 other followers

%d bloggers like this: