If you found yourself standing in Alaska during the last ice age, chances are you would meet a woolly mammoth on the move.

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But was this shaggy beast taking a quick stroll or a long hike? Was it alone, or travelling in a herd?

Well, now we know.

An international team of scientists has unravelled the travel diary of a woolly mammoth, stored in its 17,000-year-old tusk.

And it turns out the mammoth this particular tusk belonged to was indeed quite the traveller, taking enough steps over Alaska during its life to nearly circle the Earth twice.

According to a study published today in Science, building a picture of how mammoths moved around can offer clues about what led to their demise.

“When you get right down to it, there’s very little ecological information about woolly mammoths, especially their movements,” study co-author Matthew Wooller, a palaeoecologist at the University of Alaska Fairbanks, said.

“It’s filling in these little jigsaw pieces about the ecology that can help us eventually understand what caused these animals to go extinct.”

Man crouches on table with mammoth tusk

Supplied: JR Ancheta, University of Alaska Fairbanks

By analysing the ancient DNA, the researchers were able to confirm that the mammoth was male and was most likely a member of the last surviving group of its species on mainland Alaska.

But how exactly were they able to track the movements of such an ancient creature?

How researchers retraced the woolly mammoth’s steps

Like the rings of a tree, a mammoth’s tusks contain growth bands that hold a goldmine of information about its daily life.

Stacked like ice cream cones, the growth bands indicated that this particular mammoth lived for 28 years.

The bands also contained chemical signatures called isotopes, which tell the story of the places the mammoth visited.

“It’s kind of like a chemical GPS unit,” Dr Wooller said.

A split mammoth tusk in a lab with scientist in the background

Supplied: JR Ancheta, University of Alaska Fairbanks

The researchers sliced the 1.7-metre tusk into small sections to take a closer look at these isotopes using a mass spectrometer.

To build a map of the locations the mammoth visited, the team matched the isotopes in the tusk to those found in the teeth of hundreds small rodents found across Alaska.

When the researchers took a look at the first 10 centimetres of the tusk’s tip – representing the first two years of the mammoth’s life — they noticed that the strontium and oxygen isotopes were fairly consistent.

This suggested that the young animal didn’t venture out too much and spent most of its days hanging out in the lower Yukon River basin in central Alaska.

But as they moved further down the tusk, the team were able to see that the isotopes in a section spanning the ages of two and 16 years old varied a little more.

This shift in the tusk’s chemistry indicated the mammoth began exploring the grassy lowlands between the Alaska Range to the south and the Brooks Range to the north as it hit teenage-hood.

It also began making regular journeys from north to south, perhaps travelling in a herd similar to the way elephants do today.

The isotope signatures drastically changed when the mammoth was around 15 or 16 years old.

The signatures indicated the mammoth was making more long-distance trips, right up into the rugged Brooks Range above the Arctic Circle.

“That kind of puzzled us to start with,” Dr Wooller said.

Dr Wooller suspects that the male mammoth was probably forced out of the herd when it was old enough to fend for itself in a similar way to what happens in today’s elephants.

“The mothers kick these mature males out and off they go to find their own existence,” Dr Wooller said.

After a life of long walks across the Alaska’s ice age terrain, the woolly mammoth spent the last 18 months of its life at a slower pace, spending its days in a region just north of the Brooks Range.

The sudden spike in nitrogen isotopes indicated the mammoth likely died of starvation during late winter or early spring.

“It’s kind of a tragic end to the story,” Dr Wooller said.

“We don’t exactly know why it might have starved.”

Extinction detective work 

Julien Louys, a vertebrate palaeontologist at Griffith University in Queensland, said the study was crucial in building an understanding of how individual species fared in the face of environmental change.

“So often in the megafauna extinction debate, we lump all these different species together under one big group,” said Dr Louys, who was not involved in the study.  

“These kinds of megafauna species became extinct all over the world. But for the vast majority, we don’t have a good understanding of their biology.

“It’s great to see this sort of research being done. It’s all part of a bigger research goal to find out what happened with the extinction of megafauna.”

The next steps for Dr Wooller and his team are to take a closer look at lake and soil sediments to build a picture of the environment woolly mammoths lived in.

“That’s another way to chip away at the jigsaw puzzle,” he said.  

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