In the 19th century, intensive hunting brought the gray whale close to extinction. Although whales in the western Pacific are still endangered, protection efforts in the eastern Pacific seemed, at first, to have brought the population there back to pre-whaling numbers.
But new genetic research shows gray whales may once have been much more abundant than they are today. The finding suggests the world’s oceans may no longer be able to support such a large population.
The gray whales of the eastern Pacific have been considered one of the great success stories of species recovery. After being hunted to near-extinction by commercial whalers, their current population is now estimated to be about 22,000. But new data on historic gray whale populations are forcing scientists to reassess how well these whales have recovered.
Liz Alter is a Ph.D. student at Stanford University in California, and the lead author of a study that used genetic analysis to assess the historic population size of gray whales. She says the history of a population is “written in its DNA, because larger populations have much more genetic variability than smaller populations.” By measuring genetic variation in gray whales, Alter was able to estimate the average, long-term, historical size of the Pacific population.
Earlier estimates of the pre-whaling population had been based largely on historical accounts from commercial whalers, and were in the same range as the current average population estimate of 22,000.
Alter found that the genetic diversity in gray whales today is much higher than would be expected. In fact, Alter says, the measured diversity would be more typical of a population of 78,000 to 117,000. “That indicates to us that there once were many more gray whales, as many as three to five times more in the Pacific Ocean than there are now.”
That difference between historic and current gray whale populations could have serious implications for other marine species, as well, according to Stanford biology professor Steve Palumbi, a co-author of the study. He says gray whales play a key role in the ocean ecosystem