Mountain Goats Are Not Avalanche-Proof

The scene ends badly, as you might imagine.

Mountain goats are high-elevation daredevils, learning to balance upon the steepest of rocky edifices soon after they are born. Nannies lead their kids up gnarly slopes, seeking places that predators fear to tread. While the precarious perches help goats avoid being eaten, there is an obvious downside to these sanctuaries: avalanches.

While scientists have long suspected that this life on the edge was risky, they have not really understood the extent to which avalanches affect mountain goats, and whether they instinctively shun, or can learn to avoid, avalanche-prone conditions. While the behavioral question remains a mystery, a study published Monday in the journal Communications Biology, based on nearly two decades of research in Alaska, shows that cascades of snow are a major killer, substantially affecting the animals’ populations.

Kevin White, an ecologist at the University of Victoria and the University of Alaska Southeast and lead author of the study said, “We’ve often thought of snow as a major driver of populations,” of mountain goats. But the difficulty of studying their rugged, inaccessible habitats has limited understanding of what avalanches do to the animals’ numbers. That is compounded by a bias toward summertime research on the animals.

Typically, “people don’t go out in the winter, and they don’t go out in these conditions,” said Eran Hood, a snow hydrologist at the University of Alaska Southeast and an author of the study.

Over 17 years of field work with the Alaska Department of Fish and Game, Mr. White fitted radio collars on 421 goats in the Klukwan, Lynn Canal, Baranof Island and Cleveland Peninsula regions of southeastern Alaska. He surveyed the animals’ locations, following their movements from aircraft as the pulsing collars indicated whether the goats were alive or dead. When mortality was detected, Mr. White swooped in by helicopter. Then, if it was safe to land, he gathered post-mortem clues. Then he worked with a group of colleagues to make sense of the mortality data.

Data from the collared goats revealed that snow slides barreled down not just on inexperienced kids but on breeding adults as well, especially females in their prime. Avalanches were deadly, explained Mr. White, and caused 65 percent of all deaths in one of the regions studied.