Research connections reveal risks to mountain goats from avalanches in Southeast Alaska

Mountain goats use steep, exposed terrain to avoid carnivores such as wolves, but new research reveals a significant cost of this behavior – exposure to snow avalanches. Findings from a long-term study by researchers at the University of Alaska Fairbanks and the University of Alaska Southeast with partners in Canada and Switzerland show that death from avalanches represents a widespread but previously undescribed pathway by which snow can influence populations of slow-growing mountain-adapted animals.

Using field data collected from four populations in coastal Alaska over 17 years, a study published in Communications Biology revealed the importance of avalanches in driving population dynamics of mountain goats. “Avalanches transform mountain landscapes in major ways that can be both beneficial and deleterious,” said wildlife ecologist and lead author Kevin White of the University of Alaska Southeast and University of Victoria. “Our study provides the first detailed evidence of the latter, namely the striking impact avalanches can have on mountain wildlife population demography – with up to 22% of individuals killed by avalanches in a single year”.

Mountain goats are highly specialized for alpine life but survival requires negotiating precarious trade-offs. The ever-present risk of wolves and other large carnivores compel animals to inhabit steep, rugged terrain to minimize the risk of predation. However, utilizing predator-free cliffs exposes animals to slopes that regularly experience avalanches. While dangerous, avalanches may also provide sustenance when slides expose vegetation in winter and later in spring, when early-emerging “green waves” of nutritious forage appear in avalanche chutes recently swept clean of snow. Balancing risk and reward however is tricky because avalanche risk can be largely imperceptible with the unstable layers that trigger slides being buried deep within the snowpack.

The team of wildlife and snow scientists from the US, Canada, and Switzerland combined long-term field data from over 400 satellite tagged mountain goats with innovative avalanche hazard modeling techniques to conduct the study. “This project offered a unique opportunity to explore how the physical process of avalanching snow influences wildlife populations, adding to our existing ecologically-oriented understanding of snow-wildlife relationships”, said Eran Hood a Professor of Environmental Science at the University of Alaska Southeast and co-author of the study. 

Hood is the principal investigator on one of the two AK CASC-funded projects which made this publication possible. He and his co-investigators are working to understand the impact of avalanches on mountain goat populations in Southeast Alaska. Another project works to model future changes in snow avalanches across the same region and is led by Gabe Wolken with the International Arctic Research Center at UAF and the Alaska Division of Geological & Geophysical Surveys. “We developed a novel approach to modeling snow avalanches over broad areas of Alaska, which allowed us to evaluate mountain goat terrain use from the perspective of avalanche hazard exposure” said Wolken of the modeling work. “Ultimately by combining the work this study provided a unique opportunity to consider why the snow avalanche-related mortality rate for mountain goats is so high in Southeast Alaska and why it varies spatially in this region.” 

What did the team discover? The implications of avalanche mortalities for often small, isolated mountain goat populations can be profound. By monitoring radio-marked animals and examining mortality events through data sharing agreements and funding support from the Alaska Department of Fish and Game, researchers determined that over 1/3 of all deaths were caused by avalanches, occurring across nine months of the year. Additionally, unlike other causes of death such as predation and malnutrition that selectively remove immature and old animals from the population, avalanches were found to kill animals at random. As a result, avalanche mortalities included a significant fraction of prime-aged mountain goats of high reproductive value.

Mountain goats are sentinels of change in alpine ecosystems and are particularly sensitive to shifts in weather and climate. How climate change is likely to alter the prevalence of avalanches, and their influence on the species is an important area of future research. Existing evidence suggests changes will vary geographically and track projected increases in extreme weather events.

This story was modified from an original press release written by Kevin White, Eran Hood, and Chris Darimont.
Read the original UAF Press Release about this research.