Dec. 10, 2004 — Global warming could render extinct Rudolph and the rest of Santa Claus' reindeer by the end of the century, according to new research that examined fossils from a cave in southwestern France.

Occupied by both Neanderthals and, later, Cro-Magnon humans, Grotte XVI, a cave above the Ceou River in the Dordogne region of France, revealed a more than three-meter-deep layered deposits from about 60,000 to 12,000 years ago.

Lead researcher Donald Grayson, an archaeologist at University of Washington, and Françoise Delpech, a French paleontologist at the Institut de Prehistoire et de Geologie du Quaternaire at the University of Bordeaux, correlated the number of reindeer bones found in the cave with summer climate data from previously published paleobotany studies of pollen counts.

It emerged that the number of reindeer decreased as summer temperatures increased.

"At the end of the Pleistocene (about 10,000 years ago), as summer temperatures increased even more, reindeer were extirpated from this part of southern France, just as they were from the Pyrenees to the south, the Alps to the east, and elsewhere in southern Europe," the researchers wrote in a forthcoming issue of the journal Conservation Biology.

The Pleistocene extinction was not the first climatically driven disappearance of reindeer from southern France, the researchers said.

The animals were present in the region during the Riss glaciation, prior to about 130,000 years ago: during the Eemian interglacial, roughly 130,000 to 116,000 years ago, they disappeared, "returning as temperatures cooled and global ice volumes increased," the researchers said.

Today, reindeer, or caribou, are found from Scandinavia across northern Russia in Europe and roughly along the United States-Canada border in North America.

Prior to global warming at the end of the Pleistocene, the animals were found as far south as northern Spain and northern Italy. In North America, they ranged into northern Mississippi in the southeastern United States and into southern Idaho in the West.

"By the year 2080, Arctic summer temperatures are predicted to increase by 4.0 - 7.5° Celsius. This may cause heavy mortality in reindeer and caribou populations, and this mortality may be accompanied by a significant retreat of the southern boundary of the distribution of these animals," concluded the researchers.

According to Grayson, reindeer biologists have not given much thought to summer temperatures as a key factor in declining reindeer populations.

"They thought that reindeer are relatively immune to high summer temperatures. They are not, and this is the point of our study. On the other hand, reindeer are also vulnerable to a wide range of other factors, such as insects and freeze/thaw episodes in the winter, which can be expected to increase under warming conditions," Grayson told Discovery News.

According to David R. Klein, professor emeritus with the University of Alaska's Institute of Arctic Biology, the study "is a novel interpretive effort to utilize ancient bones from archaeological excavations to answer questions about the influence of a warming climate on the past environment."

"Grayson and his co-author provide insight on an important part of the complex puzzle of the reindeer extinctions in southern Europe during the climate warming at the end of the Pleistocene glaciation," Klein, one of the world's reindeer experts, told Discovery News.