When Rain Falls On Snow, Arctic Animals May Starve

Musk oxen clash horns in a battle for dominance on Alaska's Seward Peninsula. Researchers suspect that herds of reindeer, musk oxen and other Arctic animals may face starvation as a warming climate affects their ability to access food. Laurent Dick/AP

When wildlife biologists visited a remote spot in Canada called Banks Island in the spring of 2004, they discovered thousands upon thousands of dead musk oxen. It took years to determine the cause. They called it "rain-on-snow" — the worst case of it ever documented.

"Long story short, about 20,000 musk oxen starved to death because of this event," says geologist Jaakko Putkonen. It was a "humongous event" that took place in the fall of 2003.

Putkonen, who is a professor at the University of North Dakota, has since discovered a few anecdotal accounts of big rain-on-snow events that killed reindeer in the Arctic and in Scandinavia.

What happens is this: Unusually warm weather drops rain on top of snowpack. The rain either pools at the surface or trickles down to the soil below the snowpack, then freezes into a sheet of ice. Musk oxen, which are shaggy, cow-sized animals that weigh hundreds of pounds, can't break through the ice to browse on plants underneath the snow. Sooner or later, they starve.

Putkonen says it's hard to know where and how often this is happening. The Arctic is vast and remote, and one never knows where or when a rain-on-snow event will happen. Even if you put down instruments to record one, they freeze up or get snowed under. CONTINUE