"A combination of low population numbers and a species migrating between places where humans didn't bother them gave us the impression that gray whales have a stereotypical migratory and feeding behavior that may not be historically correct," Lindberg said.
The new population numbers accord with a 2007 estimate that the California gray whale population was likely 76,000 to 120,000 before humans began hunting them. That estimate, by Stephen Palumbi of Stanford University and his collaborators, was based on an analysis of gray whale genetic diversity.
The numbers clash, however, with claims by some ecologists that populations of between 15,000 and 20,000 are likely the most that the Pacific Coast specifically along the whales' 11,000 kilometer (6,900 mile) migratory route from Baja California to the Bering Sea could support, today or in the past.
"Our data say that, if the higher estimates are right, gray whales would have made it through the Ice Ages in numbers sufficiently large to avoid bottlenecking," Pyenson said. "If gray whale populations were at the lower levels, they would only have squeaked through the ice ages with populations of hundreds or a few thousand. That would have left bottlenecking evidence in their DNA."
Bottlenecking is when populations drop so low that inbreeding becomes common, decreasing the genetic diversity in the species and making them less able to adapt to environmental change.
The new assessment is good news for gray whales, which appear to have "a lot more evolutionary plasticity than anyone imagined," Lindberg said. This could help them survive the climate change predicted within the next few centuries that is characterized b
|Contact: Robert Sanders|
University of California - Berkeley