Mammoths Stranded On Bering Sea Island Delayed Extinction

In an article in the June 17, 2004 edition of the journal Nature, R. Dale Guthrie, professor emeritus at the Institute of Arctic Biology at the University of Alaska Fairbanks, says that when mammoths on the mainland of Alaska and other Bering Sea islands died out during the extinctions at the end of the Pleistocene era (about 11,000 years ago) those on the Pribilofs survived and new radiocarbon dates show how.

It was a matter of being in the right place at the right time and the mammoth tooth fossil that demonstrates Guthrie's point is the first record in the Americas of a mammoth population surviving the Pleistocene.

"During the last glacial maximum, when the sea level was about 120 meters below its current level, what are now the Pribilofs were simply uplands connected to the mainland by a large, flat plain," Guthrie said.

Using accelerator mass spectrometer (AMS) radiocarbon dating, bathymetric (water depth) plots, and sea transgression rates from the Bering Sea, Guthrie found that the mammoths became stranded on the Pribilofs about 13,000 years ago during the Holocene sea level rise after the last glacial maximum.

"Woolly mammoths became extinct on the mainland about 11,500 radiocarbon years ago," Guthrie said. At that time St. Lawrence Island was part of the Alaska mainland and presumably subject to the same extinction pressures as the mainland, but St. Paul had been an island for about 1,500 years.

"Radiocarbon-dated samples from St. Lawrence Island show similar dates of extinction to the mainland," Guthrie said, "but a sample from St. Paul dates to only 7,908 radiocarbon years old, into the mid-Holocene, which is much later."

The mammoths were able to survive on St. Paul so long as the island provided enough grazing forage and there were sufficient numbers of animals to prevent inbreeding pressures, Guthrie said, and at its present size of 36 square miles is too small to sustain a permanent mammoth population. St. Paul became that size about 5,000 years ago, so mammoths likely became extinct prior to that time.

St. Paul lies about 300 miles west of the Alaska mainland, and 750 air miles west of Anchorage.