Study takes unprecedented peek into life
of 17,000-year-old mammoth
Peer-Reviewed PublicationIMAGE: A CLOSE-UP VIEW SHOWS A SPLIT MAMMOTH TUSK AT THE ALASKA STABLE ISOTOPE FACILITY. BLUE STAIN IS USED TO REVEAL 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. view more
CREDIT: PHOTO BY JR ANCHETA, UNIVERSITY OF ALASKA FAIRBANKS
An international research team has retraced the astonishing lifetime journey of an Arctic woolly mammoth, which covered enough of the Alaska landscape during its 28 years to almost circle the Earth twice.
Scientists gathered unprecedented details of its life through analysis of a 17,000-year-old fossil from the University of Alaska Museum of the North. By generating and studying isotopic data in the mammoth’s tusk, they were able to match its movements and diet with isotopic maps of the region.
Few details have been known about the lives and movements of woolly mammoths, and the study offers the first evidence that they traveled vast distances. An outline of the mammoth’s life is detailed in the new issue of the journal Science.
“It’s not clear-cut if it was a seasonal migrator, but it covered some serious ground,” said University of Alaska Fairbanks researcher Matthew Wooller, senior and co-lead author of the paper. “It visited many parts of Alaska at some point during its lifetime, which is pretty amazing when you think about how big that area is.”
Researchers at the Alaska Stable Isotope Facility, where Wooller is director, split the 6-foot tusk lengthwise and generated about 400,000 microscopic data points using a laser and other techniques.
The detailed isotope analyses they made are possible because of the way that mammoth tusks grew. Mammoths steadily added new layers on a daily basis throughout their lives. When the tusk was split lengthwise for sampling, these growth bands looked like stacked ice cream cones, offering a chronological record of an entire mammoth’s life.
“From the moment they’re born until the day they die, they’ve got a diary and it’s written in their tusks,” said Pat Druckenmiller, a paleontologist and director of the UA Museum of the North. “Mother Nature doesn’t usually offer up such convenient and life-long records of an individual’s life.”
Scientists knew that the mammoth died on Alaska’s North Slope above the Arctic Circle, where its remains were excavated by a team that included UAF’s Dan Mann and Pam Groves, who are among the co-authors of the study.
Researchers pieced together the mammoth’s journey up to that point by analyzing isotopic signatures in its tusk from the elements strontium and oxygen, which were matched with maps predicting isotope variations across Alaska. Researchers created the maps by analyzing the teeth of hundreds of small rodents from across Alaska held in the museum’s collections. The animals travel relatively small distances during their lifetimes and represent local isotope signals.
Using that local dataset, they mapped isotope variation across Alaska, providing a baseline to trace the mammoth movements. After taking geographic barriers into account and the average distance it traveled each week, researchers used a novel spatial modeling approach to chart the likely routes the animal took during its life.
Ancient DNA preserved in the mammoth’s remains allowed the team to identify it as a male that was related to the last group of its species that lived in mainland Alaska. Those details provided more insight into the animal’s life and behavior, said Beth Shapiro, who led the DNA component of the study.
For example, an abrupt shift in its isotopic signature, ecology and movement at about age 15 probably coincided with the mammoth being kicked out of its herd, mirroring a pattern seen in some modern-day male elephants.
“Knowing that he was male provided a better biological context in which we could interpret the isotopic data,” said Shapiro, a professor at the University of California Santa Cruz and investigator at the Howard Hughes Medical Institute.
Isotopes also offered a clue about what led to the animal’s demise. Nitrogen isotopes spiked during the final winter of its life, a signal that can be a hallmark of starvation in mammals.
“It’s just amazing what we were able to see and do with this data,” said co-lead author Clement Bataille, a researcher from the University of Ottawa who led the modeling effort in collaboration with Amy Willis at the University of Washington.
Discovering more about the lives of extinct species satisfies more than curiosity, said Wooller, a professor in the UAF College of Fisheries and Ocean and Institute of Northern Engineering. Those details could be surprisingly relevant today as many species adapt their movement patterns and ranges with the shifting climate.
“The Arctic is seeing a lot of changes now, and we can use the past to see how the future may play out for species today and in the future,” Wooller said. “Trying to solve this detective story is an example of how our planet and ecosystems react in the face of environmental change.”
Other institutions contributing to the study included Florida State University, Montanuniversität Leoben, Liaocheng University and the National Park Service.
JOURNAL
Science
DOI
10.1126/science.abg1134
ARTICLE TITLE
Lifetime Mobility of an Arctic Woolly Mammoth
ARTICLE PUBLICATION DATE
13-Aug-2021
Isotopes reveal the lifetime mobility of an Arctic woolly mammoth
From the isotopes inside a 1.7-meter-long tusk, researchers recreated the life history of one Arctic woolly mammoth that lived more than 17,000 years ago, offering some of the first evidence that woolly mammoths traveled vast distances. Their findings provide a window into the lives of these now-extinct creatures, including their preferred habitats and extensive lifetime range. Despite being one of the most widely studied and iconic ice-age creatures, very little is known about the natural life history of the woolly mammoth, as fossils alone provide only static and often singular glimpses into their lives. Thus, the home range and mobility of mammoths – where and how far the large creatures roamed throughout their lives – remains largely a mystery. However, since regular migrations across great distances characterize the mobility patterns of their living elephant relatives and other Arctic animals, it is assumed that woolly mammoths exhibited similar behaviors. One method of potentially reconstructing the mobility patterns of long-dead mammoths is through the analysis of oxygen and strontium (Sr) isotopes that become incorporated into the animals’ teeth and tusks during life. Strontium isotope ratios (87Sr/86Sr) in soils and plants reflect the underlying bedrock geology, which vary across landscapes. As animals eat these plants, 87Sr/86Sr patterns from the region become incorporated into tissues. Thus, the 87Sr/86Sr ratios contained in tissues that continually grow throughout life, like mammoth tusks, for example, can provide a record that can be used to trace an animal’s movement over time. Using the tusk from a male woolly mammoth that lived in what is now mainland Alaska more than 17,100 years ago, Matthew Wooller and colleagues assembled a high temporal resolution isotopic record that reveals – in great detail – the mammoth’s movements during its ~28-year lifespan. The record shows repeatedly traveled routes across a geographically extensive range, with the animal covering enough of the Alaska landscape during its 28 years to almost circle the Earth twice. The results also illustrate the regions the animal frequented during different life stages, including as an infant and juvenile when part of a herd, as a more broadly traveling prime-aged adult, and during its final years, where, in a small region in northern Alaska, it likely succumbed to starvation.
JOURNAL
Science
DOI
10.1126/science.abg1134
ARTICLE TITLE
Lifetime Mobility of an Arctic Woolly Mammoth
ARTICLE PUBLICATION DATE
13-Aug-2021
