Learning from the past in Yukon

Reconstructing 10,000 Years of Caribou Diets from Melting Yukon Ice Patches

Dr. Carson Hedberg and team on an expedition to the Gladstone Ice Patch

A prestigious NSF Postdoctoral Fellowship from the Office of Polar Programs that was awarded to Carson Hedberg is powering a new Kartzinel Lab project in the Yukon: using ancient DNA preserved in towering alpine ice patches to reconstruct thousands of years of change in caribou diets since the end of the last Ice Age. By sequencing genetic traces of food that have been locked inside caribou dung and literally frozen in time, Carson is asking how these animals have weathered past climate shifts—and what this can tell us about prospects for their future.

Learning From the Past to Protect the Future

Northern mountain woodland caribou are a culturally and ecologically vital, yet threatened, species of the Arctic. In summer, they crowd onto high-elevation ice patches to escape biting insects, leaving behind layers of dung that become entombed in ice for millennia. As those ice patches are rapidly melting under modern climate change, they are exposing a rare, time‑stratified archive of caribou ecology that may soon disappear.
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This project combines paleoecology, GPS tracking, and remote sensing to build a detailed time series of caribou dietary change and ice-patch dependence that could ultimately stretch back in time for 10,000 years. By pairing ancient DNA metabarcoding with modern satellite collar data, the team is working with First Nations and territorial partners to understand how caribou depend on ice and how ongoing ice loss will reshape their ranges

Dr. Carson Hedberg and team climbed a 200-ft vertical ice face to extract ancient DNA that will teach us about 10,000 years of change in caribou diets

Why Study Caribou Diets in Ice?

Caribou (Rangifer tarandus) are increasingly at risk of disappearing. Across their circumpolar range, many herds have shrunk by more than 50% in the last century. For wildlife managers, First Nations, and northern communities who depend on caribou, planning for an uncertain future is difficult.

Paleoecological records can offer powerful lessons from the past to help us predict the future. If we can see how caribou responded to past environmental fluctuations, we can better anticipate how they might respond to the rapid warming and ice loss that they have to survive today.

Ice Patches as Time Capsules

Carson Hedberg's postdoctoral fellowship focuses on northern mountain woodland caribou, a threatened population that gathers on alpine ice patches to escape heat and biting insects in the summer. As animals return to the same ice patches year after year, they leave behind layers of dung that becomes frozen in ice that accumulates each year.

The DNA contained within dung pellets that were deposited centuries or even millennia ago has been cryopreserved ever since. As these endangered ice patches to melt due to modern climate warming, they are exposing dung and other artifacts to the elements. It’s a unique, climatically threatened archive of caribou ecology that could soon disappear.
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Carson’s NSF‑funded research has already produced a collection of specimens that span at least the last 4,000 years and that could ultimately date back about 10,000 years to the end of the last Ice Age. Then, using dietary DNA metabarcoding—a genomic method to identify foods caribou ate using plant and fungal DNA that has been preserved in the dung—she will generate taxonomically precise profiles of dietary change.

Ancient caribou dung has been extracted from ice blocks where it has been cryopreserved for thousands of years in the Gladstone Ice Patch.

Pairing Ancient DNA with Modern GPS Collar Data

​To connect the paleorecord of ancient DNA to the ecology of living animals, Carson's project also leverages GPS-collar data from modern Yukon caribou. Working closely with the Yukon Department of Environment, the team obtained a rich dataset covering multiple herds in southern Yukon.

By modeling when and where collared caribou visit ice patches, the team will quantify how strongly caribou depend on ice, how ice influences their habitat selection and foraging ranges, and how these behaviors may shift as the endangered ice ultimately shrinks to the point of disappearing. This modern behavioral assessment will be essential for interpreting the ancient DNA record and for forecasting the ecological impacts of ongoing ice loss.

​Building Partnerships in the Yukon

In the first year of the project, much of the Carson's work focused on fostering relationships. Carson traveled multiple times to Yukon, Canada to meet with territorial agencies and First Nations communities.
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The team is working closely with the Yukon Department of Tourism and Culture and the Yukon Department of Environment to secure access to samples and data and to ensure that project outcomes align with territorial conservation priorities. With a data-use agreement in hand, the lab aquired a trove of GPS collar data that is now being processed.

Equally important are partnerships with the First Nations on whose lands the ice patches sit. Carson and collaborators presented project objectives to representatives from multiple First Nation communities in southern Yukon. Based on their guidance, the team agreed to target an ice patch in the traditional territory of Champagne and Aishihik First Nations (CAFN) for intensive dung sampling. They co‑developed a Material Transfer Agreement that demonstrates exemplary planning for ethical sample collection, data sharing, and the long‑term stewardship of knowledge.

​Fieldwork on the Gladstone Ice Patch

In September 2025, after months of planning and logistics, Carson led a major sampling expedition to the Gladstone Ice Patch in the CAFN traditional territory. Reaching the site required the team to commute by helicopter with the support of a technical mountaineering team.

With the help of two professional ice‑climbing guides, the team spent three days collecting dung from a 200‑foot vertical transect of dung‑rich ice. They used chainsaws to cut blocks from the melting ice, then slung them beneath the helicopter for transport to refrigerated storage truck in the nearby town of Haines Junction.

These remarkable efforts under challenging conditions yielded a set of samples that span thousands of years and the team is already learning from them!

Dr. Carson Hedberg commuted by helicopter to the Gladstone Ice Patch

​From Frozen Pellets to DNA Sequences

After collection, the ice blocks were shipped to the University of Alberta. There, in temperature‑controlled labs, the team used specialized saws to carefully isolate caribou dung pellets from the ice, minimizing contamination and preserving DNA.

So far, we have more than 50 dung samples spanning the last ~4,000 years. Our first sequencing experiments have revealed remarkable DNA preservation in these ancient pellets. Soon, we will generate high‑resolution data on both the plant and fungal components of caribou diets from the mid‑Holocene to the present.

Conserving Endangered Ice

The research is not only about extracting dung before it is exposed to the elements; it is also about protecting the breadth of physical, chemical, and biological information these ice patches can provide as a long‑term scientific and cultural resource. As climate change accelerates the loss of alpine ice across the Arctic, this project demonstrates how paleoecology, genomics, and community‑driven conservation can work together: using the past, preserved in ice, to inform decisions about the future of caribou and the people who rely on them.