During the summer of 2016, a gold miner in Canada’s Yukon Territory found an unexpected treasure. As he blasted a wall of permafrost with a water cannon to uncover the riches inside, Neil Loveless saw something melting out of the ice. This was not a valuable mineral, but rather the oldest and most complete wolf mummy ever discovered.
So Loveless quickly put the frozen pup in a freezer until paleontologists could take a look. They discovered that the well-preserved animal was a young female that was part of a vanished ecosystem from a time when northwestern Canada was home to American mastodons and other Pleistocene megafauna. Local Tr’ondëk Hwëch’in people named the 57,000-year-old juvenile Zhur, which means “wolf” in the language of their community.
Exceptional mammals have already been retrieved from the Siberian tundra, also dating from the Pleistocene, a period from about 2.6 million to 11,700 years ago, also known as the Ice Age because ice caps at the poles were much larger than they are today. However, finding such an intact wolf in the Yukon is unprecedented.
“In Siberia, such preservation is fairly common because permafrost preserves things there, which is much less common in the Yukon, Alaska and other parts of North America,” said paleontologist Julie Meachen of Des Moines University, lead author of a study describing Zhur published today in the journal Current Biology. After tens of thousands of years, much of Zhur is still intact, from its fur to the delicate papillae on its tongue.
“The preservation looks amazing,” University of Copenhagen paleontologist Ross Barnett, who was not involved in the study, says. But there is more to Zhur than what can be seen with the naked eye. “She tells us a lot,” Meachen said, from her age at death – seven weeks – to what she ate. Research offers a glimpse into a period of resurgence between glacial stretches of Earth’s history.
A lost wolf population
The Zhur lived during an interglacial period when the giant Arctic glaciers temporarily retreated and forests replaced the cooler grasslands. This was a time of mastodons, camels, giant beavers and, as Zhur documents, gray wolves.
“The extraordinary preservation of a carnivore is a unique situation to look at glacial ecosystems from the perspective of a predator,” says McMaster University paleogeneticist Tyler Murchie, who was not involved in the study.
Despite being an integral part of modern North American wildlife, gray wolves did not evolve in the Americas. Such canids first appeared in Eurasia and crossed the Bering land bridge late in the Pleistocene, more than 500,000 years ago.
“Zhur comes from a time period that is not well known in the Yukon as far as mummies go,” Barnett says. And by examining the remains of the wolf pup’s DNA, Meachen and colleagues found that this animal documents a group of wolves that no longer exist in the region.
Zhur belonged to a population that had genetic links to wolves in both Alaska and Eurasia, but wolves living in the Yukon today have a different genetic signature. The results suggest that the first gray wolves in the Yukon were extirpated and later replaced by other populations that had already established themselves farther south.
“Ancient DNA consistently shows how much more complex evolutionary histories and paleoecology are than we might otherwise infer from studies of bones and fossils,” Murchie says. Without Zhur’s genes, this extinction and replacement would have been invisible to scientists.
An abbreviated prehistoric life
Zhur’s body also tells us something about her life. When she died, she was only about seven weeks old and had just passed the weaning age at which she would have begun to eat more solid foods. The geochemical signatures in her teeth indicate that she fed on meals from rivers and streams, perhaps fish such as Chinook salmon, which still spawn in the rivers near where she was found. Many modern wolves in interior Alaska feed similarly, eating fish rather than big game.
Unfortunately, Zhur’s life was short. She appears to have died in a cave collapse, with the quick burial facilitating the extraordinary preservation of her body. Some other mammals from this period – such as Arctic ground squirrels and black-footed ferrets – have been preserved in the same way.