• Marmots in the Swiss Dischma-valley now live at altitudes on average 86 metres higher than in 1982 but remain below the known upper limit of 2,700 metres. Climate change alone only partially explains this shift.
• Soil depth, snowpack and food plants are key factors in explaining why most animals are currently concentrated at an altitude of around 2,500 metres.
• Their habitat is shrinking because the treeline is rising; marmots need open spaces and cannot move to higher elevations.

Climate change is causing marmots to move, but not far: this is the conclusion of a recent study by SLF biologist Anne Kempel. She investigated the altitude at which most marmots currently live and compared her findings with data from 1982. Her assumption was that the animals were moving to higher altitudes because of the warmer temperatures caused by climate change. “But that’s only partly true,” says the researcher.

In fact, the majority of the animal families she observed in the Dischma Valley near Davos live around 86 metres higher than they did 42 years ago, at around 2,500 metres above sea level. Kempel concludes that the conditions there are apparently ideal for marmots. “But the absolute upper limit hasn’t shifted,” she explains. This limit is 2,700 metres above sea level, as was already the case in 1982.

“Other factors probably play a more important role than warmer temperatures,” notes Kempel. Too high up, the animals would not find any soil in which to dig their extensive burrows. In addition, during hibernation they need as thick a snowpack as possible to insulate the ground from the cold. “We find most of these conditions exactly where most groups now live,” says the biologist.

Habitat depends on multiple factors

Moreover, plants containing linoleic acid are an important part of this animal’s diet. This unsaturated fatty acid regulates body temperature in winter. “These plants may have shifted their range slightly upwards,” Kempel suspects.

Kempel and her team adopted the same methods as their predecessors in 1982. For one to two hours at a time, they observed 25 areas on the slopes of the Dischma Valley using telescopes and binoculars and counted the marmots they saw. Statistical computer models then extrapolated the probable population, leading to the surprising conclusion.

However, their observations only apply to the Davos region and possibly similar areas. “We don’t have historical data for other locations,” says Kempel. In lower parts of the Alps, conditions could become difficult for the animals, as they suffer from heat stress at temperatures above 25 degrees Celsius. They then retreat to their burrows for long periods during the day and so eat less fat for the winter – with fatal consequences in the cold season.

Climate stress and rising treelines threaten marmots’ habitat

In the long term, this could also become a problem at higher altitudes, as it is getting warmer there too. “But the Dischma Valley still only sees an average of six days per year with temperatures above 25 degrees, which is too few to have a negative impact,” Kempel reassures us.

Nevertheless, there is already less space, given that the treeline is slowly but steadily shifting upwards. “Marmots prefer open habitats. They aren’t suited to living in forests, and since they aren’t moving further up into the mountains, their habitat is shrinking,” explains Kempel.