Illustration of an adult male woolly mammoth. Image: James Havens/ University of Alaska Museum of the North.
Some 17,000 years ago, a male woolly mammoth traversed tens of thousands of miles across Alaska before it died on the northern slope of the Brooks Range at the age of 28. Now, scientists have managed to reconstruct intimate details about the life of this extinct individual, which are written in the chemical composition of a tusk it left behind. The bygone mammoth walked an astonishing distance of about 43,000 miles (70,000 kilometers)—equal to nearly twice the circumference of Earth—according to a study published on Thursday in Science. After growing up with its family herd, the male struck out as an adult around age 15 and wandered widely across the northern wilderness for more than a decade until it likely starved to death during a harsh winter or spring season.
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A team of interdisciplinary scientists were able to retrace its steps across Alaska by deciphering isotopes of strontium and oxygen preserved in its tusk and matching them with locations across the state.“There is very little information on Arctic woolly mammoth movement patterns at all, and not at this level of detail,” said study co-lead Matthew Wooller, director of the Alaska Stable Isotope Facility at the University of Alaska Fairbanks, in a call. “There are other studies that have analyzed isotopes in parts of tusks, cores going into tusks, and juvenile tusks, but this is really the first for a full lifespan of a mature mammoth. It’s unusual like that.”This detailed window into the life of an extinct creature is partly a result of recent advances in mapping and modeling concentrations of isotopes, which are versions of elements with varying numbers of neutrons, across vast landscapes such as Alaska. Clément Bataille, an isotope geochemist at the University of Ottawa who co-led the study, has been building these complex maps, or “isoscapes,” using bones collected across Beringia, the northern region that once linked Siberia and North America. In this study, Bataille and his colleagues focused on isotopes found in rodent teeth, which reveal the local isotopic signatures of various regions because these small animals do not travel very far.
“This is very recent, and the technologies that have helped us to map strontium isotopes have been machine learning and artificial intelligence,” Bataille said in a joint call with Wooller. “Some of these new statistical algorithms have really helped us map strontium isotopes more precisely than we could ever do before.”Because mammoths grew their tusks in banded layers over the course of their lifetimes, much like the rings of a tree, each new band contains isotopic signatures that act like geographic trackers. To check the travel history and odometer of this particular mammoth, the team split its tusk and read through the interior layers, from the bands left in its final days all the way back into its infancy.
The results revealed that the mammoth racked up an extraordinary distance in its lifetime, especially after it was presumably kicked out of its family herd as a teenager—a rite of passage that some male elephants also experience at around the same age. After its departure from its family, the mammoth began to range into the Arctic Circle much more frequently, covering tens of thousands of miles while it presumably searched for food or mates.“It was a real surprise that this was, we think, very analogous to modern elephant behavior,” Wooller said. “There was a distinctive change in range and movement pattern. The animal spent a lot more time at higher elevations and further north during that mature stage.”
Mammoths and modern elephants not only share ancestral and behavioral similarities, but also many of the same existential pressures. Climate changes and human activity have been implicated in the eventual extinction of mammoths, and they are also forces that shape the fates of elephants, along with many threatened species, today. “Our work does help put together the jigsaw puzzle of what caused mammoths to go extinct; it's one more little piece of that puzzle going forward and that's of value,” Wooller said. “I think the other value is that our work also shines light on some of the concerns we have for current modern Arctic megafauna: polar bears, caribou, marine mammals, and others, that are having to change their behaviors, ecologies, and movement patterns in response to current observed Arctic warming, and environmental changes that are resulting from that.”“There’s a power of wonder in doing this sort of work, and thinking about these magnificent creatures, and about preserving them in the present day,” Bataille added. “We have elephants that could be extinct in 100 years. We look at this mammoth and we are really amazed by this crazy animal, but in 1,000 years, maybe future generations could just be looking at an elephant the same way. That's also a wakeup call for preserving some of these species.”In this way, the new study has pioneered new avenues of research that have applications for understanding the past, present, and future of Earth and its inhabitants, including humans. Having established their novel approach, Wooller, Bataille, and their colleagues plan to continue using isoscapes to reconstruct the movements and life stages of other animals, perhaps as far back in time as dinosaurs. The ability to intimately follow the footsteps of long-dead individuals is not only a useful scientific technique, it’s also a way to bring the eventful stories of these animals back to life in a way that can resonate for everyone.“You get really attached to his movements and you get sad, actually, when you end up at 28 years and he just dies there,” Bataille said. “You think: ‘That’s too bad. Maybe he could have gone in another direction and done something else.’” “I like this study, because there’s a link on a personal level,” he concluded. “Here’s this individual, and his little story, as if he was right there in front of us.”