Ancient squirrels ate meat like 'zombies,' and the proof is in the poop

It smelt. That was the first thing Tyler Murchie noticed when he opened up a sample that had sat frozen for hundreds of thousands of years in the permafrost of Canada's Yukon. These weren’t your average fossils; they had not gone through the slow mineral replacement that turns old dinosaur dung to stone. All the organics were still in there, perfectly intact, still pungent, and absolutely packed with genetic gold.

According to a June 2026 study published in Nature Communications by Murchie and his colleagues at the Hakai Institute in British Columbia, those fossilized feces, known as coprolites, are not just the byproduct of a small rodent’s bathroom habits. They are detailed biological records of a whole lost world: one that included woolly mammoths, American cheetahs, steppe bison, horses, wolves and hundreds of plant and insect species that once defined Ice Age North America.

The oldest samples are approximately 700,000 years old. If those age estimates hold, then the DNA sequences pulled from them would be some of the oldest ever retrieved from any living organism on Earth.


How squirrel poop became a scientific goldmine
The Klondike region of Canada’s Yukon has a long history of gold fame. Miners, too, have been showing up, using high-pressure jets of water to melt away deposits of permafrost and finding ancient ground squirrel burrows and the coprolites packed inside them.

Murchie’s team analyzed 13 of those frozen fecal samples, from roughly 700,000 to 17,000 years ago. That period, called the Pleistocene, was an age of ice ages, when huge herds of megafauna traveled across North America.

It was no easy feat to get readable DNA from ancient poop. According to Willerslev et al. (2003), a foundational study published in Science, one of the few places where ancient DNA can be preserved for hundreds of thousands of years is permafrost. But ancient feces pose a special extra challenge: they are full of natural compounds that inhibit the enzymes used to decode genetic sequences. Murchie’s team needed to do a lot of work to tweak their method, reducing sample sizes and improving chemical cleanup before the material finally provided usable results.

What came out was amazing. Genetic material was recovered from the coprolites of woolly mammoths, American cheetahs, steppe bison, horses, caribou, wolves, birds, insects, parasitic worms, and more than 200 plant species. Researchers reconstructed about 20 complete mitochondrial genomes from the material.

Zombies of the Pleistocene
To understand why a ground squirrel’s poop contains mammoth DNA, you need to understand how ravenous these animals are when they wake up from hibernation.

Ground squirrels can spend up to eight months of the year in a deep, torpor-like sleep. When they come out in the spring, they are, as Bryan McLean, an evolutionary biologist at the University of North Carolina at Greensboro, put it, “desperate for protein and high-quality diet items.” McLean has personally seen them eating roadkill, including their own kind.

According to Grabek et al. (2019), published in Communications Biology by researchers at Stanford University, the genetics of hibernation in ground squirrels drive extreme physiological cycles. The act of emerging from torpor is an intense one, with heart rates jumping from roughly three beats per minute to normal levels in just a couple of hours, something researchers compare to surviving a heart attack. This process leaves animals metabolically primed and desperate for food.

In the Ice Age Yukon, squirrels apparently went straight for whatever carcasses were lying around, including the remains of woolly mammoths and big cats. “You can imagine these squirrels emerging from the ground, starting to eat carcasses lying in the environment. They're zombies of the Pleistocene,” Mikkel Pedersen, a molecular palaeoecologist at the University of Copenhagen who peer-reviewed the study, said in an email.

A species hiding in plain sight
But beyond the ecosystem snapshot, the study revealed a surprising finding about the squirrels themselves. Researchers identified the remains as Arctic ground squirrels (Urocitellus parryii), the same species that lives in the Yukon today, but ancient DNA analysis revealed they belonged to a previously unknown lineage. In fact, it is much closer to the long-tailed ground squirrel (Urocitellus undulatus), a species now found in Siberia, Mongolia, China, and Kazakhstan. For decades, scientists had assumed that the ancestor of today’s Arctic ground squirrel lived in the Ice Age Yukon, based on fossilized remains. The DNA says the opposite.

These coprolites are “exceptional repositories for understanding evolutionary and ecological change through the deep past,” said Hendrik Poinar, Director of McMaster University’s Ancient DNA Center and a senior author on the study. A separate paper dealing exclusively with the mammoth DNA sequences is in preparation and should yield further findings.

A tiny creature, an enormous legacy
Ground squirrels are not the charismatic megafauna shown in the Ice Age documentaries. Mammoths get the museum displays, cheetahs get the dramatic reconstructions. But it turns out the humble ground squirrel and its frozen droppings might contain more detailed information about those lost worlds than any fossil ever could.

“A mammoth bone will tell you a mammoth was here,” Jacquelyn Gill, a paleoecologist, quoted in coverage of the study. “These ground squirrel coprolites are telling you we had a ground squirrel here eating these plants, living among these insects, sharing the landscape.”

Murchie noted that the study also offers a glimpse into a warmer-than-today climate period dating back some 115,000 years ago, which may help scientists understand what human-caused warming could look like over the long term.

The permafrost is melting. The archives may not stay frozen for much longer.