Are nest boxes always the best method for monitoring glirid populations? Insights from Eliomys Quercinus in the alps

Abstract Monitoring wildlife is crucial for understanding the impacts of human activities on species and informing conservation strategies. The garden dormouse ( Eliomys quercinus ) has experienced significant range loss and population decline across Europe. The species distribution is fragmented, and data on its population size is limited, necessitating effective monitoring methods. This study evaluates the effectiveness of nest boxes in monitoring garden dormouse populations in alpine habitats. In 2019, we started a long-term monitoring project to study dormice ecology and distribution in the western Italian Alps. Nest boxes were installed in six areas along an elevational gradient from 1,200 to 2,000 m a.s.l. and monitored for dormouse presence. From 2019 to 2021, only three nest boxes were occupied by garden dormice. However, from 2022 onward, the species’ presence increased significantly, with 8 and 10 nest boxes occupied in the lower-elevation areas in 2022, followed by a more regular presence in the subsequent years. Footprint tunnels placed near each nest box in 2022 confirmed the presence of the species even in areas where dormice did not enter the nest boxes. These findings suggest that garden dormice in the Alps do not immediately utilise nest boxes, unlike in other European regions. This behaviour is likely due to the unique mountain habitat, where garden dormice prefer ground cavities between rocks over tree cavities and nest boxes. Our findings highlight the importance of considering habitat characteristics when designing monitoring programs for the species.