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1 min read Nature

Zombie Squirrel of the Pleistocene Feasted on Mammoth Meat

Permafrost-preserved squirrel feces just rewrote what we thought we knew about Ice Age ecosystems. What else hides in those frozen burrows?
Field Notes

Field Notes

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Ground squirrels have a reputation. Industrious. Herbivorous. Faintly nervous-looking. That reputation is now 700,000 years out of date.

A study published June 9 in Nature Communications analyzed ancient DNA extracted from frozen squirrel feces (coprolites, to give them their proper dignity) recovered from permafrost burrows in the Klondike region of Yukon, Canada. The 700,000-year-old coprolites revealed that when these ancient Urocitellus ground squirrels woke from torpor, they ate a diverse diet of plants, insects and carcasses of megafauna, including woolly mammoths, bison and big cats. The big-cat DNA is its own puzzle: it belonged to either the North American cheetah (Miracinonyx trumani) or pumas (Puma concolor).

The mechanism is not mysterious once you understand ground squirrel physiology. Ground squirrels spend many months in a winter slumber, then awake ravenous and eat anything in sight. Molecular palaeoecologist Mikkel Pedersen of the University of Copenhagen labeled the ground squirrels "zombies of the Pleistocene" imagining them emerging from hibernation and then feasting on the carcasses scattered nearby.

What makes this study genuinely significant beyond its vivid imagery is the archival quality of the material. The coprolites preserved not just what the squirrels ate, but a comprehensive snapshot of an entire vanished ecosystem: over 200 plant species, invertebrates including parasitic worms, rodents, bats, birds and megafauna DNA, all reconstructed from frozen feces. Researchers assembled 18 mitochondrial genomes from the samples. The DNA sequences reveal a previously unknown lineage of ground squirrel and, potentially, North America's oldest mammoth DNA.

The broader finding is methodological. Permafrost-preserved coprolites preserve ancient environmental DNA more richly than either bone or sediment from the same sites. The Yukon has hundreds of such middens still unexamined.

A small, nervous-looking rodent was quietly archiving the Pleistocene ecosystem one meal at a time.

Read the full story at Scientific American, June 9, 2026

Hot Take:Feces outperforming bone as a DNA archive points to palaeogenomics spending decades looking in the wrong drawer.

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