National Geographic: Greenland’s caribou work up quite a hunger during their long migrations. But global warming now has the animals arriving late for dinner–and paying a heavy price. Fewer caribou calves are being born in the western part of the Danish island, and those that are born have slimmer chances of surviving, a new study reports. The declines are tied to availability of the willows, sedges, and flowering tundra herbs that caribou and their newborns feed on in spring. As global …