Last of the Woolly Mammoths Died in 'Catastrophic' Event on Wrangel Island 4,000 Years Ago, Study Claims

The last population of woolly mammoths appears to have died off after a "catastrophic" event, having survived in isolation in relatively stable environmental conditions for 7,000 years, a study has found.

By analyzing changes to their diet, nutrition and metabolism, researchers found little to suggest the species was under pressure, and so believe an extreme weather event that led to a large number of mammoths to starve to death may have been responsible for their extinction.

Woolly mammoths disappeared around 4,000 years ago, having become isolated on Wrangel Island—a remote, Arctic island that was cut off after sea levels rose at the end of the last ice age. The population survived on the island for far longer than its mainland counterparts. Mammoths in Russia disappeared about 15,000 years ago, while they survived on Saint Paul Island in Alaska until about 5,600 years ago. Previous research has shown there were major changes to the habitats of both populations before their demise as a result of climate change, suggesting this played a role in local extinctions.

"No one had looked at what was going on with the dietary ecology of the Wrangelian mammoths, and with all these other observations related to diet, it was high time to do so," Laura Arppe, from the Finnish Museum of Natural History, told Newsweek. "We wanted to look at the dietary ecology of the mammoths in order to see if we could find signs of changes in their diet, nutrition or metabolism leading up to extinction, e.g. if we could see signs of starvation or malnutrition."

Arppe and colleagues have now looked at mammoth bones and teeth found on Wrangel Island and compared them with other populations of mammoths. They looked at carbon and nitrogen isotopes that provide information on nutrition and metabolic functioning in the thousands of years before they went extinct. Their findings are published in the journal Quaternary Science Reviews.

"Judged from the numbers of radiocarbon dated mammoth bone finds on Wrangel island, this last island population appears to have vanished rather abruptly. There [are] no signs of a dwindling population size before the extinction," Arppe said. "[It's] kind of like they hit a wall at approximately 4,000 years ago. All the major changes in climate and range size had taken place long ago: the change to the warm Holocene climate at about 10,000 years ago, the isolation of the island and its reduction to present-day size at about 8,000 years ago.

"So as judged from what previous proxy studies have shown about their environment, they seem to have disappeared from amidst stable conditions. Why?"

The team found the Wrangel Island mammoths were comparable to their Siberian counterparts in terms of dietary wellbeing. However, there were some key differences. The Wrangel Island mammoths appear to have used fats as a dietary resource differently—results indicate they relied on their fat reserves to survive the colder winters. The mammoths in warmer climates did not need to do this, Arppe said.

The researchers did not find evidence of any "alarming long-term changes" in the habitat or climate in the Wrangel Island mammoths. As a result, they say a short-term event appears to have pushed the species to extinction.

They suggest "icing events" may have severely harmed the population. This is where rain on snow causes an area to become covered in ice, preventing access to food. "These types of events have been known to cause deaths of large numbers of large herbivores in the arctic. 20,000 musk oxen were starved to death in 2003 in the Canadian Arctic due to a rain-on-snow event," Arppe said.

The mammoths, the team conclude, may have starved to death as a result of this short-term environmental crisis.

They also found evidence that weathering may have led to a reduction in access to freshwater, which may also have played a role—something they now plan to investigate.

"Our next step is to study these [severe water quality issues] to either reject or confirm the hypothesis, that from time to time, the drinking water supply of the animals had high levels of harmful or even toxic elements released from the local bedrock, that might have affected the population's fitness," Arppe said.

Love Dalén, from the Swedish Museum of Natural History, who was not involved in the study, told Newsweek the finding that there was no deterioration in food availability was robust: "This is very interesting, since one of the main hypotheses for the extinction of the Wrangel population has been that a change in vegetation took place in the mid-Holocene.

"Also, the observation that such a deterioration in food composition has been found in some mainland populations, but not on Wrangel, provides an insight into why mammoths became extinct at the end of the Ice Age on the mainland, but not Wrangel."

However, he also said the idea that a "catastrophic" event caused their extinction was "highly speculative."

"Right now, we have no evidence either way, apart from that gradually decreasing food quality likely wasn't the cause," he explained.

This article has been updated to include quotes from Love Dalén.

woolly mammoth
Artist impression of a woolly mammoth. Researchers say the last population of woolly mammoths went extinct after a catastrophic event that may have caused them to starve to death. iStock