Autumn on the Alaskan tundra was a whole new spectacle. With ground-hugging shrubs—all of them circumpolar species who grow around the top of the globe—instead of tall trees, it looked like the land itself was drenched in a rainbow swirl of melted crayon. But caribou were the official reason I’d come here, to the Toolik Field Station on the North Slope of the Brooks Range in 2018.