Earlier this year, researchers brought an ancient giant virus back to life. Now, they have recovered more viral genetic material—this time from frozen caribou feces. For more than 5 millennia, caribou have grazed shrubs and grasses on ice patches atop the Selwyn Mountains in Canada. The animals congregate on the subarctic ice patches during warm summer seasons to escape heat and biting insects, leaving layers of feces on the ground. After drilling ice core containing thousands of years of accumulated caribou dung (shown above), scientists recovered the complete genome of a DNA virus and the partial genome of an RNA virus from frozen feces dated to 700 years old, they report online today in the Proceedings of the National Academy of Sciences. Genetic sequencing identified the RNA genome as a member of the insect-infecting Cripavirus genus, but the DNA viral genome was more mysterious: It was unlike any sequenced present-day viruses, but distantly related to plant-infecting geminiviruses. So the researchers reconstructed the DNA virus and introduced it to Nicotiana benthamiana, a close relative of tobacco that’s vulnerable to a diverse range of plant viruses. The resurrected virus successfully infected both new leaves and leaves inoculated with the virus. The researchers suggest that the viruses may have originated in plants eaten by the caribou or in flying insects attracted to their feces. As Arctic ice melts faster with climate change, it could release ancient viral particles into the environment—some of which could remain infectious, the team warns.