Winter rain, an unusual event in the high north, drives animal numbers on a Norwegian Arctic island into decline, showing that extreme climate events can affect an entire community of vertebrates.
Brage Hansen at the Norwegian University of Science and Technology, Trondheim, and his team found that populations of Svalbard reindeer (Rangifer tarandus platyrhynchus), rock ptarmigan (Lagopus muta hyperborea) and sibling voles (Microtus levis) on the island of Spitsbergen crash during especially rainy winters — when the animals' food is coated in layers of ice. The extreme weather synchronizes fluctuations in the population numbers of these herbivores. This, in turn, causes numbers of the Arctic fox (Vulpes lagopus; pictured) — which preys on ptarmigans and voles, and feeds on reindeer carrion — to oscillate, but with a one-year lag.
The overwintering vertebrate community could represent a bellwether for the influence of global warming on Arctic ecosystems, if climate change raises the prevalence of warmer and wetter winters.