Shifting Heights? A 40-Year Resurvey of Alpine Marmot Distribution in Response to Climate Change

Alpine species are severely affected by climate change, with elevational range shifts being one key response of mountain species to the rapidly warming environment. The Alpine marmot (Marmota marmota) is suggested to be particularly susceptible to ongoing warming. However, it is largely unknown how climate change affected the Alpine marmot distribution in recent decades. This study examines the elevational changes in Alpine marmot distribution over the past 40 years in a Central Alps Mountain valley. Based on historical occurrence data of the year 1982, we resurveyed the marmot occurrences in the year 2022. We analysed potential distributional changes over time by fitting dynamic site-occupancy models to detect occupancy patterns, as well as marmot colonisations and site abandonments ('local extinctions' at a site) along the elevational gradient, whilst accounting for imperfect detection. Contrary to expectations, we found no evidence of upward colonisation at higher elevations or an upward shift of the lower range margin in our study, suggesting that marmots are not climate-limited at lower elevations in the investigated valley, and other factors than climate might constrain their higher elevation colonisation. Nevertheless, the marmot's elevational optimum shifted upwards by +86 m. Our results indicate that the most favourable conditions for marmots have slightly shifted higher due to warming. To better understand potential habitat contractions driven by climate change, further large-scale studies focusing on the lower range margins in warmer Alpine regions are necessary. Recognising distribution changes of species vulnerable to climate change is crucial to evaluate local extinction risks and for conserving biodiversity.