A cross-section detail of the mammoth’s tusk, with blue stain revealing growth lines. Samples were taken along the tusk using lasers and other techniques, allowing isotope analysis that provided a record of the mammoth’s life (Photo: JR Ancheta, University of Alaska Fairbanks).
The tip of the tusk is the oldest part, and the base is the youngest. The team split the tusk into two and used a special instrument to analyse the isotope ratios in the tusk — they focused on strontium, but also looked at oxygen, carbon and nitrogen.
Once they had analysed the isotope ratio, they could figure out where the mammoth had travelled on the landscape.
“What’s really nice is that the geology of the (Alaska) region is extremely complex, one of the most complex geologies that exists in the world,” says Bataille. The complexity is good, he says, because there’s different types of rock all over the place, with different isotope ratios, making it more obvious where the mammoth travelled. “The mammoth is really moving on the landscape, the changing geology, very, very rapidly.”
The scientists constructed millions of possible walk routes, and found that only a few could have possibly fitted with the isotopes.
As a juvenile, the mammoth moved a bit less when he was with his maternal herd. Then, at 15 to 17 years of age, the mammoth was kicked out of his maternal herd and moved much more on the landscape. “He would just take off and do a lot of kilometres, like 500 or 600 kilometres in two months, going to very different areas,” says Bataille. It was hypothesized that when the mammoth became sexually mature, he travelled much further between maternal herds.
“The long distance movement might reflect also a resource need, and resource use,” says Bataille, “because the Arctic is a place with really harsh landscapes and with limited resources on the tundra. So maybe at some point, some areas become drier, or the climate is not as good in some regions — and so the mammoth just takes off.”