Other grazing species, like caribou or Dall sheep, also may be harmed by increasing rain in the Arctic, Dr. Bowyer said: “It bodes poorly for big mammals.”
A decade ago, Dr. Berger began traveling to Alaska to gather data on musk oxen. Each summer, he and his colleagues cruised across the frozen tundra in a sort of snow tractor until they found a herd.
Rather than running away, the animals would form a defensive circle. Dr. Berger used long-lens cameras to snap photographs of individuals and bounced lasers off them to determine how far away they were.