This Ice Age wolf puppy doesn’t look much like a terrifying predator, with her tiny puppy teeth and soft ears. According to her DNA, the mummified puppy named Zhùr came from a population that is one of the ancestors of all modern wolves. Canada’s permafrost freeze-dried her remains shortly after her death about 57,000 years ago.
She is the most complete wolf mummy ever found. She’s essentially 100 percent intact – all that’s missing are her eyes, ”said paleontologist Julie Meachen of Des Moines University.
Puppy surprise
In July 2016, miner Neil Loveless of Favron Enterprises was looking for gold in Alaska’s famous Klondike gold fields. He blew the frozen mud along the banks of Last Chance Creek. It’s a process called “ hydraulic thawing, ” meant to thaw and soften the frozen permafrost so that miners can search for gold in the stream deposits, an approach called placermining. But Loveless found something much weirder and even more interesting than Klondike gold: a frozen, mummified wolf puppy.
“We thank [Loveless] for his keen gaze that Zhùr saw as she melted from the permafrost, made sure she was kept safe in a freezer, and then reported the discovery to Yukon Paleontology, ”Meachen and her colleagues wrote in a recent article in the journal Current Biology. Studying the Pleistocene wildlife in the Yukon means working with gold mining companies, whose employees may be the first to see anything like Zhùr. Scientists such as Meachen also work very closely with the people who have called this region home for thousands of years, such as the Tr’ondëk Hwëch’in First Nation.
Members of the group gave the puppy its name, Zhùr, which means “wolf” in the Hän language. Zhùr is a culturally significant find for the Tr’ondëk Hwëch’in, but they were also interested in how much the frozen puppy could teach us about Pleistocene wolves. The First Nation agreed to exhibit the mummy at the Yukon Beringia Interpretive Center in Whitehorse, where it has been cleaned, preserved, and studied.
“We are grateful for partnering with Tr’ondëk Hwëch’in in our shared role in protecting and preserving heritage resources in the Klondike,” wrote Meachen and her colleagues.
Taking small samples from some of Zhùr’s incredibly well-preserved hair follicles, Meachen and her colleagues dated radiocarbon with the frozen puppy and studied the chemical isotopes in her body, which provided clues about what she ate and the climate in which she lived. They also sequenced her mitochondrial DNA, the genetic material that was passed directly from mother to offspring.
The ancestors of modern wolves
Zhùr probably lived about 57,000 years ago, but it took three different dating methods to find out.
Radiocarbon dating could only tell Meachen and her colleagues that the mummy was older than 50,000 years. The puppy’s genome suggested she lived somewhere between 75,000 and 56,000 years ago, based on the rate at which wolf DNA collects mutations over time. And the oxygen isotopes in her body suggested she had lived during the relatively warm period of Marine Isotope Stage 3, when warmer conditions led to smaller ratios of the isotope oxygen-18 in marine sediment cores – and in Zhùr’s body. MIS 3 covered a period from 57,000 to 29,000 years ago.
All those possible dates overlapped at one point: 57,000 to 56,000 years ago. At the time, the sea level was much lower than it is today, and a dry land called Beringia connected Siberia with Canada. Animals moved freely back and forth between the continents, which is why Pleistocene wolves excavated in Eurasia and North America are all so closely related. Zhùr’s mitochondrial DNA fit right into that group of closely related animals, or clade, with a common ancestor that lived between 86,000 and 67,500 years ago.
Zhùr and her clade are the ancestors of every wolf in the world (except possibly the high-altitude Himalayan wolves, which have apparently been doing their own thing for hundreds of thousands of years, according to a study earlier in 2020).
But because mitochondrial DNA is passed directly from mother to puppy, Meachen and her colleagues could see that Zhùr was not a direct ancestor of the wolves that roam the Klondike today. Sometime in the past 56,000 years, the Klondike wolf population became extinct or left the area, and another group of wolves – a less closely related to Zhùr – replaced it. At this point, there isn’t enough data to tell if the newcomers drove away, competed, or simply absorbed Zhùr’s family members, but the puppy’s DNA suggests an interesting story that has yet to be explored.
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A prospector found the mummified puppy and kept her in a freezer until paleontologists could pick her up.
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Conservators cleaned the mummified puppy and even carefully brushed her fur.
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The pup’s remains are dried out but largely intact from being buried in permafrost.
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X-rays showed how fully the puppy’s bones were developed, which paleontologists used to estimate her age.
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The puppy’s teeth are largely intact, as are the details of her lips and gums.
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Permafrost mummies are very delicate and you should not bend the snoot.
Wolves also eat fish
If Zhùr Meachen and her colleagues couldn’t tell exactly what happened to an entire population of Klondike wolves, she could at least tell quite a bit of her own story. Based on how her bones had developed, the puppy was about 7 weeks old when she died. Since modern wolves in the area usually give birth in early summer, this means that Zhùr likely died in July or early August, around the same time Loveless washed her out of the permafrost 57,000 years later.
Zhùr’s mother had probably weaned her puppies from milk and started bringing them real food. Modern wolf puppies start eating solid food when they are about 5 or 6 weeks old. In Zhùr’s case, that seems to contain a lot of fish, depending on the amount of isotope nitrogen-15 in her body. Nitrogen isotopes provide clues about how far along the food chain an animal is and whether its food came from land or water.
Considering all the fish, the puppy’s breath must have been horrible. “Normally, when you think of Ice Age wolves, you think of them eating bison or musk oxen or other large land animals,” Meachen said. “One thing that surprised us was that she was eating aquatic resources, especially salmon.”
Modern wolves in inland Alaska have been known to chew on fish, at least in seasons when they are readily available. And Zhùr’s burrow was not far from the Klondike River, where the Chinook salmon spawn today. The fish swim up the Yukon River to the Klondike, where they would have been a real buffet for a mother wolf who wanted to feed her pups.
How to freeze-dry an Ice Age predator
Obviously, Zhùr didn’t end well, otherwise we wouldn’t have a ridiculously cute dog-like ice cream mummy to study today. Her funeral may provide a few clues as to her untimely end and her eerily good preservation throughout the intervening millennia. She must have died in exactly the right circumstances and buried quickly – a rare combination. “The animal has to die in a permafrost site, where the ground is constantly frozen, and they have to be buried very quickly, as with any other fossilization process,” Meachen said.
Animals killed by predators tend not to form perfectly preserved ice mummies, and animals that die from disease or exposure are also not buried fast enough to freeze and mummify. And isotope analysis suggests the puppy was well fed, so no matter what happened, she probably wasn’t sick and certainly not starving.
Meachen and her colleagues believe that Zhùr’s lair collapsed, killed her immediately, and buried the remains in the icy ground. “We feel a little bit better knowing the poor girl didn’t suffer too long,” said Meachen.
However, there is one more question that Zhùr will never be able to answer: why was she alone in the den? Wolf mothers usually have four to six puppies at a time, but only Zhùr was buried next to Last Chance Creek; no sign of her mother or littermates has surfaced. “It could be that she was an only pup, or that the other wolves weren’t in the den during the collapse,” Meachen said. “Unfortunately, we will never know.”
A warning tail
Permafrost mummies of large mammals, such as mammoths, bears, and even wolves, are rare finds for paleontologists. But smaller ones, such as ground squirrels and ferrets, are more likely to show up in places like Siberia and the Yukon. Meachen and her colleagues speculate that animals that lived in burrows or burrows, including wolf cubs, were more likely to be kept in the permafrost, especially if they died in collapses.
Even large mummy finds from permafrost are becoming more common. Earlier this year, a cave bear emerged from Siberian permafrost and it is one of many recent finds. “A small benefit of climate change is that we will find more of these mummies as permafrost melts,” Meachen said. “That’s a good way for science to better reconstruct those times, but it also shows us how much our planet is really warming up.”
Current Biology, DOI 2020: 10.1016 / j.cub.2020.11.011 (About DOIs).