Fossilized ground squirrel excrement reveals 700,000 years of environmental history

Ground squirrel burrows preserved in the permafrost of Yukon, Canada, contain fossilized excrement dating back several hundred thousand years. These remains, called coprolites, provide exceptional access to ancient environmental DNA, allowing the reconstruction of past ecosystems with unprecedented precision. Genetic analyses have revealed the presence of plants, insects, microbes, and even large mammals characteristic of the mammoth steppe, an environment now extinct. Among the most remarkable discoveries are complete mitochondrial genomes of iconic species such as the steppe bison, horse, and woolly mammoth.

This excrement also made it possible to identify an unknown lineage of Arctic ground squirrels, dating back 700,000 years, predating the divergence of several current groups. This discovery suggests an unsuspected genetic diversity in these rodents, adapted to the extreme conditions of the Arctic. Ground squirrels, in fact, hibernate for long months, lowering their body temperature below zero and their heart rate to just one beat per minute, a unique survival strategy in the animal world.

Coprolites stand out for their ability to preserve eukaryotic DNA, often better than bones or sediments. Researchers were able to confirm the authenticity of this ancient DNA through characteristic degradation patterns, rigorous positive and negative controls, and taxonomic validations via computer simulation. Contrary to expectations, little contamination from external materials was observed, proving that these excrement act as airtight biological time capsules.

The ecosystems reconstructed from these samples correspond to those of Eastern Beringia, a region that, during the Pleistocene, was home to flora and fauna now extinct. The dominant plants included grasses, willows, and birches, while the animals included mammoths, bison, horses, as well as predators such as American lions or American cheetahs, species now extinct. The coprolites even revealed traces of parasites, such as nematodes, uncovering complex ecological interactions.

The study shows that ground squirrel burrows, often overlooked in paleogenomics, constitute an unparalleled source for understanding the ecological and evolutionary dynamics of the Quaternary. Their analysis could revolutionize our understanding of species adaptations to past climate changes, offering valuable lessons for the future. The researchers emphasize that these natural archives, preserved in the permafrost, may still hold many secrets about prehistoric life.

Official Sources

Reference Study

DOI: https://doi.org/10.1038/s41467-026-72977-6

Title: Ground squirrel coprolites preserve complex archives of ancient environmental DNA over 700,000 years

Journal: Nature Communications

Publisher: Springer Science and Business Media LLC

Authors: Tyler J. Murchie; Scott L. Cocker; Sina Baleka; Nicola Alexandra Vogel; Libby Natola; Emil Karpinski; Diana Tirlea; McIntyre A. Barrera; Danielle M. Grant; Evan Morien; George S. Long; Linda Y. Rutledge; Grant D. Zazula; Britta J. Jensen; Duane G. Froese; Hendrik N. Poinar