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DNA Fingers Real-Life Captain Ahabs for Precipitous Decline of Gray Whales

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gray whale drawing

Gray wale, Eschrichtius robustus (page 455). - After Scammon, "Marine Mammals of the North-West Coast of North America", New York 1874, drawn by P. Neumann/Wikimedia Commons

Tens of thousands of whales were slaughtered each year for decades from the mid 1800s to the early 1900s, in the service of lighting city streets, painting ladies’ lips and providing multitudinous other modern conveniences.

This monomaniacal hunt led many species to the brink of extinction. But recent research has suggested that gray whale (Eschrichtius robustus) populations in the Pacific might have already been on their way down. So are the real life Ahabs really off the hook—at least for the gray whale’s plight?

Getting a picture of pre-whaling whale populations is tricky. Early- and mid-19th century population estimates and whaling records can be as convoluted as Queequeg’s tattoos. And attempting to estimate ancient populations by assessing contemporary populations’ DNA relies on assumptions that do not always hold water.

Historic data estimated the pre-1850 gray whale population to be somewhere between 15,000 and 20,000, whereas genetic estimates puts that number at 19,500 and 35,500.

A more solid tale of whale populations and their distributions is of interest not just to historians but also to policy-makers seeking insights into restoring contemporary gray whale populations, which are still less than a third of what they likely once were. So scientists have been curious to get a sense of how many of these Pacific whales there really were.

gray whale vertebra

Gray whale vertebra image courtesy of Wikimedia Commons/Jlikes2Fish

A team led by Elizabeth Alter, of Stanford University’s Hopkins Marine Station, undertook an effort to set the record straight. They harvested DNA from gray whales captured or beached along the northern Pacific coasts of the U.S. and Canada both recently and historically. The researchers compared contemporary whale DNA to that sampled from whalebones uncovered at archeological digs of indigenous fishing villages that ranged from 150 to 3,500 years old.

According to the analysis, there was, indeed, a severe population bottleneck. But it didn’t happen before the Pequods of the world set out for their cetacean prizes. So it probably wasn’t the “Little Ice Age” (cooling from 1300 to 1850), predation from killer whales (Orcinus orca) or increased hunting by indigenous populations that took the gray whale to the edge of evolutionary obscurity.

The new genetic data reveals that this bottleneck probably occurred about 93 years ago (or about six whale generations ago), which would have been in the final furious push of industrialized whaling. During this time, there were only about 9,070 gray whales left in the eastern Pacific. Before that population pinch, the area likely was home to more than 60,000 of these massive, 16-meter-long creatures.

The work underscores the difficulties of using modern genetics alone to estimate ancient animal populations. “Historic baselines for many marine populations [might be] much larger than previously estimated,” the researchers wrote in their paper, published online May 9 in PLoS ONE.

So, thanks to some clever new analysis, these old whalebones proved worth their salt in helping us understand whale populations in the era before we humans started launching our harpoons. And Melville’s characters—and their actual analogues–remain implicated in the crime.

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Jerzy v. 3.0. 5:39 am 05/10/2012

    It would be interesting to check DNA from extinct Atlantic population of grey whales. It was sometimes claimed to be different species, although recently, surprisingly, stray Pacific grey whale swam to the Atlantic.

    Link to this
  2. 2. OttaSotta 10:56 am 05/10/2012

    Tens of thousands of whales were caught in the modern era (1910s onward). Only a few to several thousand were caught annually during the peak of open-boat whaling (1835-1860).

    Link to this

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