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Wildlife in the mountains and the cost of living are dangerous

Photo by Kevin White
Close-up of an adult male mountain goat near the Juneau Icefield in late winter. Steep, avalanche-prone slopes can be seen in the background.

Mountain goats use steep, exposed terrain to avoid carnivores such as wolves. But new research shows that this behavior comes at a significant cost: you're exposed to snow avalanches.

Results 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 common but previously uncharted pathway through which snow can affect populations in slow-growing mountains -adapted animals.

Using field data collected over 17 years from four coastal Alaskan populations, a study published in Communications Biology demonstrated the importance of avalanches to the population dynamics of mountain goats, an iconic species in North American mountain cultures and landscapes.

The comprehensive study was funded by the Alaska Climate Adaptation Science Center, hosted by UAF, as part of its mission to understand climate impacts on Alaska's land, water, animals and people.

“Avalanches alter mountain landscapes in significant ways that can be both beneficial and harmful,” said wildlife ecologist and lead author Kevin White of UAS and the University of Victoria. “Our study provides the first detailed evidence of the latter, namely the striking impact that avalanches can have on the demographics of mountain wildlife populations, with up to 22% of individuals being killed by avalanches in a single year.”

To conduct the study, the multidisciplinary team of wildlife and snow scientists from the United States, Canada and Switzerland combined long-term field data from over 400 satellite-tagged mountain goats with innovative avalanche hazard modeling techniques.

“This project provided a unique opportunity to examine how the physical process of snow avalanche affects wildlife populations, adding to our existing ecologically-oriented understanding of the relationships between snow and wildlife,” said Eran Hood, professor of environmental science at the University of Alaska Southeast and co-author of the study.

Described by author Douglas Chadwick as a “climbing bearded animal the color of winter,” mountain goats are alpine ungulates that include 32 species in 70 countries. They are highly specialized for life in the Alps, but their survival requires negotiating precarious compromises.

The ever-present threat of wolves and other large carnivores forces them to inhabit steep, rugged terrain to minimize the risk of predation. However, the predator-free cliffs expose the animals to slopes where avalanches regularly occur.

While avalanches are dangerous, they can also provide access to food. Slides expose vegetation in the winter and later in the spring when early emerging “green waves” of nutritious food appear in recently cleared of snow avalanche slides.

However, it is difficult to balance risk and return. Avalanche risk can be difficult to detect because the unstable layers that trigger slides are buried deep in the snowpack.

The impact of avalanche mortality on small, isolated mountain goat populations can be profound.

By monitoring radioactively tagged animals and studying mortality events, researchers found that more than a third of all mountain goat deaths were caused by avalanches in nine months of the year.

Unlike predation and malnutrition, which selectively remove immature and old animals from the population, avalanches kill animals at random. As a result, a significant proportion of avalanche mortality occurred in mountain goats of prime age and high reproductive value.

How climate change will alter the frequency of avalanches and the resulting impacts on the species is an important area of ​​future research. Existing evidence suggests that changes will vary geographically and follow the predicted increase in extreme weather events. These dynamics will affect the diversity of mountain goats and other alpine species and have important implications for their future viability and resilience.

As an Ice Age relic of today's Pleistocene landscapes, mountain goats are guardians of change in alpine ecosystems because they are particularly sensitive to changes in weather and climate.

UAF

Anna Harden

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