More than 17,000 years ago, a woolly mammoth now known as the Kik wandered far and wide across Alaska during its 28-year life.
When Kik was young, he spent most of his time inland Alaska, a less mountainous area. Then, when he turned 15, his movement patterns changed, spending much more time heading north to what is now the Arctic Wildlife Refuge and the National Petroleum Reserve.
For a few years, Kik wandered with the seasons. In other years it stayed largely in the same area throughout the year.
In the last few years of his life, his movement slowed and he was confined to a smaller area above the Arctic Circle. When he was 28 years old, Kik was still middle-aged for a mammoth.
This map, showing where Kik roamed during his life, was pieced together by studying the signatures of elements trapped in one of his curved two and a half meter long tusks, and offers a glimpse into these hairy, elephant-like mammals.
“This is a better understanding of how they behaved and what environment they used,” said Matthew Wooller, director of the stable isotope facility at the University of Alaska, Fairbanks and lead author of an article published Thursday by Science magazine that the Describes results.
The data could also feed into the debate about the decline of the woolly mammoth after the end of the last ice age. Did the early humans hunt them to extinction? Was it a changing climate that they couldn’t adapt to?
“Our work also speaks a little by filling in a little of the puzzle,” said Dr. Wooller. “If you want to find out the causes of extinction, you have to know a little more about the behavior and ecology of the organisms involved.”
Most mammoths disappeared about 10,000 years ago – only recently on evolutionary and geological time scales – and not all fossil remains have turned to rock. This allows DNA to be extracted from bones and sequenced, which helps answer rough questions like how closely related mammoths in Alaska were to those in Siberia.
But the genetic information says little about how a mammoth lived. Has it migrated with the seasons? Did it spend its youth in one region and its adulthood elsewhere?
By studying the isotopic signatures in Kik’s tusk, Dr. Wooller and his colleagues answer these questions.
“If you took all those wobbly lines and straightened them out, it could have gone around the earth almost twice,” he said.
The results impressed Brooke Crowley, a professor of geology and anthropology at the University of Cincinnati who was not involved in the study.
“It’s pretty amazing how much you can learn from tiny snippets of material from an animal that is now extinct,” she said in an email. “I am particularly impressed that the authors have been able to follow the movements of this single mammoth throughout its life.”
To reconstruct Kik’s whereabouts, Dr. Wooller and his colleagues explain the fact that tusks grow layer by layer – a structure reminiscent of stacked ice cream cones. When Kik was a baby, the tip of the tusk stuck out.
During a video call, Dr. Wooller got to the base of the tusk and said, “This surface here is basically the day it died.”
In between was a record of practically every day of his life. “If you zoom in with the microscope,” said Dr. Wooller, “you can see individual day bands.”
In addition, Alaska has a rich variety of rock formations, each with different mineralogical fingerprints, which are reflected in the plants growing there. The researchers focused on strontium, an element that occurs in four stable versions, or isotopes.
So every day Kik nibbled on grass that contained levels of strontium that mirrored those of the rock below, and those same levels of strontium were worked into that day’s layer at the base of the tusk.
Similar analytical techniques have been used on teeth. But it was more difficult to use with a long, unwieldy, curved tusk. Access to the microscope required careful use of brute force.
Among the hundreds of mammoth tusks found, kiks excavated in 2010 near a river that gave it its nickname were well-suited for this research. They were in good shape and both were recovered together.
“Finding a pair of tusks is pretty rare,” said Dr. Wooller.
This, and the presence of parts of his skeleton, gave scientists assurance that Kik had died where he was found and that the remains had not been pushed there by a glacier or flood. The bones enabled them to do a genetic analysis that confirmed that he was a male mammoth. The fact that there were two tusks made them less remorseful that they cut one of them in half.
“It’s pretty heavy,” said Dr. Wooller. “And you think about it a lot. Before you commit, practice too. “
They cut up what he called a “no data tusk” – one that has no recorded information about where and when it was found, and therefore of little scientific use. First they cut a tiny canal along one side. Then they marked points halfway around the tusk. With a big band saw – “It’s as big as a person,” said Dr. Wooller – cut the tusk in half and carefully guided the blade between the channel and the markings on the other side.
Next, they cut off Kik’s tusk.
“It took us most of the day to share this thing,” said Dr. Wooller. “Six of us and then a very, very large band saw.”
He added, “Even over the noise of the band saw, the sometimes quite loud crackling and popping sound was nerve-wracking,” he said. “We thought, ‘Aug, we’re going to destroy this thing. It will fall apart when we get to the end. ‘ But it didn’t. It was really, really great. “
After the tusk was cut in half, the scientists used a laser to knock off spots along the length for isotope analysis. From there, a computer program compared the strontium concentrations with a map of the Alaskan rocks and calculated the most likely route Kik took. The scientists also examined other elements such as oxygen, nitrogen and carbon, which provided complementary information about the ecology.
When Kik died, the world was still at the height of the last Ice Age, but glaciers weren’t yet flowing over most of Alaska. Instead, the surrounding area appears to have been dry, cool grasslands, perhaps similar to the steppes of modern-day Mongolia. “It provided a wonderful environment for mammals to move about,” said Dr. Wooller.
As with some modern elephant species, where young males are thrown from female-led herds by the age of 15 or 16, Kik may have had a rather lonely life.
“That was really wonderful to find,” said Dr. Wooller. “In many ways, it was almost exactly the same as the behavior we see in modern elephants.”
An increase in nitrogen isotopes was a distinctive signature that indicated death from starvation at the end of his life.
“Kind of cool to think that we not only determined his movement patterns, but probably what caused his death,” said Dr. Wooller.
Why Kik starved to death, maybe a drought had withered the landscape or he had been injured in a fight, which restricted his mobility.
Although Kik circled much of Alaska, it apparently never went west, over the land bridge that connected Alaska with Russia at the time. That could suggest that the intercontinental crossing was not an easy route. “Some people believe it was very, very wet and swampy and insidious,” said Dr. Wooller.
Kate Britton, an archaeologist at the University of Aberdeen in Scotland who was not involved in the research, said scientists need to be careful not to translate Kik’s movements into behavior of woolly mammoths as a species.
She found that her research using similar techniques showed that members of the same species of modern caribou behaved in different ways – some migrated long distances with the change of seasons, others stayed in narrower regions – depending on where they lived, and Information about the animals’ daily life was not found in their genes.
“We need these kinds of studies that give us this access to this direct information,” said Dr. Britton. “We can infer the behavioral ecology of extinct species.”
In future research, Dr. Wooller saw and examine more mammoth tusks. Have the movement patterns changed over the millennia with climate change? Have female mammoths and their herds been to different parts of Alaska?
He said what happened to the woolly mammoths as the world warmed at the end of the last age could also point to an understanding of the animals living in Alaska today.
“We are seeing polar bears and caribou change their biology and behavior in response to some of the warming,” said Dr. Wooller. “There are parallels that we can also draw.”