The world’s last population of woolly mammoths (Mammuthus primigenius) lived on Wrangel Island, currently some 140 km off the coast of the Chukotka mainland in northeastern Siberia. They went extinct 3,700 years ago and, according to the frequency of their remains from the island, the extinction was extremely abrupt. In a new study, published in the journal Quaternary Science Reviews, an international team of researchers has investigated the ecology of the mammoth population on the island and reconstructed the scenario that could have led to their extinction.
The woolly mammoth (Mammuthus primigenius) at the Royal BC Museum, Victoria, British Columbia. Image credit: Tracy O / CC BY-SA 2.0.
“During the last Ice Age — some 100,000 to 15,000 years ago — mammoths were widespread in the northern hemisphere from Spain to Alaska,” said study lead author Dr. Laura Arppe, a scientist at the University of Helsinki, and her colleagues.
“Due to the global warming that began 15,000 years ago, their habitat in Northern Siberia and Alaska shrank.”
“On Wrangel Island, some mammoths were cut off from the mainland by rising sea levels; that population survived another 7,000 years.”
In the study, the researchers examined the isotope compositions of carbon, nitrogen, sulfur and strontium from a large set of mammoth bones and teeth from Northern Siberia, Alaska, the Yukon, and Wrangel Island, ranging from 40,000 to 4,000 years in age.
Their aim was to document possible changes in the diet of the mammoths and their habitat, and to find evidence of a disturbance in their environment.
“The results showed that Wrangel Island mammoths’ collagen carbon and nitrogen isotope compositions didn’t shift as the climate warmed up some 10,000 years ago. The values remained unchanged until the mammoths disappeared, seemingly from the midst of stable, favorable living conditions,” they said.
“The result contrasts with the findings on woolly mammoths from the East European plains, which died out 15,000 years ago, and on the mammoths of St. Paul Island in Alaska, which disappeared 5,600 years ago. In both cases, the last representatives of these populations showed significant changes in their isotopic composition, indicating changes in their environment shortly before they became locally extinct.”
Earlier studies indicate that the Wrangel Island mammoths suffered mutations affecting their fat metabolism.
In this new study, the authors found an intriguing difference between the Wrangel Island mammoths and their Siberian predecessors: the carbonate carbon isotope values indicated a difference in the fats and carbohydrates in the populations’ diets.
“We think this reflects the tendency of Siberian mammoths to rely on their reserves of fat to survive through the extremely harsh ice age winters, while Wrangel mammoths, living in milder conditions, simply didn’t need to,” Dr. Arppe said.
The bones also contained levels of sulfur and strontium that suggested the weathering of bedrock intensified toward the end of the mammoth population’s existence. This may have affected the quality of the mammoths’ drinking water.
“Our study shows that Wrangel Island maintained through the Holocene, and possibly until the present day, environmental conditions suitable for a typical mammoth ecological niche,” the scientists said.
“The exact cause of final extinction for the Wrangel Island mammoths remains equivocal, but we suggest it was likely caused by a short-term crisis, possibly linked to climatic anomalies or/and geochemical factors.”
“Furthermore, anthropogenic influence should not be ruled out despite lack of tangible evidence of hunting.”
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Laura Arppe et al. 2019. Thriving or surviving? The isotopic record of the Wrangel Island woolly mammoth population. Quaternary Science Reviews 222: 105884; doi: 10.1016/j.quascirev.2019.105884
