Mountain hare distribution in Valle Orco (Gran Paradiso National Park) and spatial overlap with the European hare

Climate change is leading to an increase in average temperatures forcing some species to migrate to higher latitudes or altitudes. The mountain hare (Lepus timidus) is an Arctic-Alpine species that evolved in the Alps through geographic isolation from northern populations after the last glaciation. The species is generally distributed between 1300 and 2800 m and is adapted to the climatic conditions and habitats present in this context. A research conducted in 2009 recorded the distribution of the mountain hare in the higher part of Orco Valley (Gran Paradiso National Park – Piedmont region) and highlighted the presence of the European hare (Lepus europaeus) at high altitudes. In 2021, we repeated the 2009 survey with the aim to: 1) investigate how the distribution of the mountain hare changed in the last 12 years; 2) assess if the European hare’s expansion in altitude increased since 2009; 3) evaluate how the range of the two species overlap. Faeces of Lepus spp. were collected in 47 sites, in circular plots and along transects located between 1544 m and 3010 m and also monitored in 2009. Non-invasive genetic techniques based on mtDNA were used to determine the species and sex of the animals who frequented the sites. Faeces of Lepus spp. were found in 17 sites (36% of the total). The mountain hare was detected in 14 sites, mainly at high altitudes; at low elevations the presence of the species was less common than in 2009. The European hare was detected in 9 sites, compared to 5 in 2009. Sites with the presence of both species increased from 4 to 6. For 2021, genetical analyses confirmed the presence of males and females of the two species in all the 6 co-occurrence sites. In 2009, the mountain harewas dominant at all altitudes, while in 2021, the European hare was slightly more common from 1544 to 2270 m, and the two species were present in the same number of transects up to 2470 m; only at the highest altitude, up to 3010 m, the mountain hare was the only recorded species. Our results highlight a contraction in the distribution area of the mountain hare in the last 12 years. In this period, the European hare has risen in altitude, invading the range of the alpine species. This situation of syntopy between the two species may favor hybridization, a phenomenon already described in the Alps and Scandinavia. Climate change and rising temperatures favor the European hare and relegate the mountain hare to high altitudes. However, the mountain hare will not be able to climb much above 3000 m due to the lack of suitable herbaceous habitats and the prevalence of rocks. Considering the continuous increase in temperatures, the possibilities for active conservation of the mountain hare are minimal. In some non-protected areas, the European hare may be actively controlled to reduce the risk of hybridization, but the survival of the mountain hare will still depend on its adaptability to higher temperatures and changing habitats.