On Norway’s frosty northern coast, a cave sat virtually unknown to humans for over 75,000 years. This remote area of the European Arctic is now granting paleobiologists a glimpse of the ancient animal communities that called this region home. The ancient remains of at least 46 animal species are helping researchers re-examine the last ice age’s precarious ecological past–while serving as a warning for the future. Their findings are detailed in a study published on August 4 in the Proceedings of the National Academy of Sciences (PNAS).
During the 1990s, Norway experienced an increase in industrial mining projects. Many of these required workers to build extensive tunnel systems into rocky mountainsides. In 1991, a local company’s drilling efforts unexpectedly uncovered a 42.6 foot deep sediment deposit inside the Arne Ovamgrotta cave. While Arne Ovamgrotta and the larger Storsteinhola cave system weren’t naturally accessible until the mining, they were available to animals as recently as roughly 71,000 years ago, during the last glacial ice age.
Arne Ovamgrotta remained largely unexplored for almost 30 years until 2021. A research team led by the University of Oslo and Bournemouth University finally organized an excavation survey. They hoped any potential discoveries would help experts contextualize the region’s distant environmental past.
“We have very little evidence of what Arctic life was like in this period because of the lack of preserved remains over 10,000 years old,” senior author Sanne Boessenkool explained in a statement.
After months of digging, Boessenkool and collaborators eventually cataloged the area’s oldest known animal remains. Humans apparently didn’t visit Arne Ovamgrotta until the 1990s, but it’s clear a wide array of other species made use of the cave—often as their final resting place. In total, researchers confirmed bones from 46 different species of mammals, birds, and fish: ancient polar bears, Atlantic puffins and cod, walruses, and bowhead whales.. The team even discovered remnants of collared lemmings, a species now extinct across Europe and never before documented in Scandinavia.
Such animal diversity implies that the cave and surrounding coastal areas were mostly thawed 75,000 years ago. While still technically in an ice age at the time, the period was markedly warmer. Temperatures were even high enough to melt nearby glaciers and provide a home for fauna including migratory reindeer. Nearby harbor porpoise bones also recovered by the team indicate that any sea ice that managed to form was seasonal at best, since the aquatic mammals typically avoided them. Freshwater fish remains also revealed the tundra must have included rivers and lakes.
However, these populations ultimately could not adapt as needed. The region’s warming climate 75,000 years ago wasn’t an end to the ice age. Instead, temperatures actually decreased once again, ushering another era of glacial waters and ice sheets. Entire animal communities subsequently died out when they couldn’t migrate to different ecosystems. Further DNA testing showed none of the documented species withstood their colder world.
“This highlights how cold adapted species struggle to adapt to major climatic events. This has a direct link to the challenges they are facing in the Arctic today as the climate warms at a rapid pace,” explained study first author Sam Walker.Â
Walker also cautioned present-day animals living in the region face “much more fractured” habitats that make survival even more challenging. Meanwhile, Boessenkool highlighted a stark detail to consider.
“It is also important to note that this was a shift to a colder [climate], not a period of warming that we are facing today,” she said. “And these are cold adapted species—so if they struggled to cope with colder periods in the past, it will be even harder for these species to adapt to a warming climate.
By continuing to study these bones and similar finds, Walker and colleagues hope to aid animal conservation efforts amid a warming world—one in which 12 percent of Norway’s species are classified as threatened. Highlighting cold-adapted species’ vulnerabilities can also help inform new ways to support their resiliency, and better understand their extinction risks.
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