Gray Whale Numbers Remain Greatly Reduced - Study
Date: 12-Sep-07
Country: US
Author: Will Dunham
Knowing that an examination of genetic variation within a
species can help gauge past population numbers, the scientists
used a US government tissue collection to analyze DNA samples
from 42 gray whales.
The genetic variation seen among these whales indicated a
past population far bigger than the current 22,000, researchers
at Stanford University and the University of Washington wrote
in the Proceedings of the National Academy of Sciences.
They determined that before large-scale hunting of this
species began in the 19th century, there were about 96,000 gray
whales in the Pacific Ocean -- with as many as many as 118,000
and as few as 76,000. That would mean the current count is 19
percent to 29 percent of the pre-hunting population.
The gray whale is a large baleen whale -- a "filter feeder"
that feasts on large amounts of small sea creatures -- that
first swam the world's oceans perhaps 20 million years ago.
"The gray whale population is one of the few baleen whale
populations thought to have recovered completely from whaling.
In other words, it was thought that there are as many gray
whales now as there ever were," Stanford marine biologist Liz
Alter, one of the researchers, said in a telephone interview.
"But when we surveyed genetic diversity we found a much
higher level of diversity than we would have expected given the
size today, indicating that there once were many more gray
whales in the Pacific Ocean than there are now," Alter added.
HUNTED TO THE BRINK OF EXTINCTION
This marine giant was hunted to the brink of extinction,
with the population bottoming out at perhaps a few thousand by
the end of the 19th century and through the 1920s, the
researchers said. The gray whale disappeared from the Atlantic
Ocean centuries ago, with some experts blaming whaling.
The gray whale migrates along North America's Pacific Coast
between arctic seas and the lagoons off of Mexico's Baja
California. It was given its name due to the gray patches and
white mottling on its dark skin.
They are about 46 feet (14 meters) long and weigh up to 40
tonnes. Gray whales feed off the sea bottom, scooping up mud
and eating small crustaceans and tube worms found in
sediments.
The gray whale was given partial protection in 1937 and
full protection in 1947 by the International Whaling
Commission, the American Cetacean Society said.
Once hunted in large numbers, gray whales now attract whale
watchers along North America's Pacific coast.
The whales are still occasionally hunted. Five Washington
state American Indian hunters may face prosecution from their
Makah tribe after illegally shooting and killing a gray whale
on Saturday with harpoons and a rifle often used to hunt
elephants.
A number of gray whales have been spotted by scientists in
recent years suffering from starvation. The researchers said
their findings suggest the whales have less to eat due to
changing climate conditions in their Arctic feeding grounds.
The researchers said other animals also may have been
affected by the diminished numbers of the gray whale. Fellow
Stanford researcher Steve Palumbi said Arctic seabirds foraged
on creatures dug up by the whales as they fed on the bottom.
Palumbi said that 96,000 gray whales would have helped feed
more than a million seabirds annually.