Ecological consequences of extreme climatic events: from small mammals community composition to population dynamics and ticks encounter in the Italian Alps

Climate change is intensifying extreme meteorological events and altering ecosystem disturbances globally, with mountain regions being particularly vulnerable. In Europe, an average of two extratropical storms strike annually, leaving wind as the primary driver of forest destruction [1]. In 2018, the Vaia windstorm, an extreme meteorological event, hit the Italian Alps toppling an estimated 40 million trees across 41,000 hectares in north-eastern regions [2]. As part of the PNRR and BEPREP project, we investigated how catastrophic disturbances influence small mammal community composition, dynamics, and tick burden [3]. The study was conducted in the Paneveggio-Pale di San Martino Natural Park (Trento, Italy). We selected two habitat types – Vaia windthrow and undisturbed forest (non-Vaia) – at two contrasting altitudinal levels: low (1,100 m a.s.l.) and high (1,650 m a.s.l.). From 2022 to 2025, we performed seasonal capture-mark-recapture (CMR) of small mammals and screened for tick infestation. Spatially explicit capture-recapture (SECR) models were used to estimate rodent density and space use, while generalised linear mixed models (GLMMs) were applied to analyse the effects of habitat disturbance, host condition, and altitude on tick burden. We captured 468 individuals including Apodemus flavicollis, A. sylvaticus, Clethrionomysglareolus, Microtus spp., and Sorex spp. Small mammal species richness was higher in Vaia windthrows than in undisturbed forests, characterised by the presence of Microtus spp. and an increased relative abundance of shrews and density of C. glareolus, while contracting the spatial range of the latter. Interestingly, Apodemus spp. density was primarily driven by altitude. Of the 295 Ixodidae ticks counted, 73% were found in windthrow areas. Tick burden was highest at low altitude sites and among heavier males in both C. glareolus and Apodemus spp. Notably, a significant increase in tick burden was observed in C. glareolus in Vaia-affected areas. Natural reforestation in windthrow areas creates complex, heterogeneous habitats that modulate small mammal community composition, density, and space use [4]. These successional environments promote host-parasite encounters, potentially enhancing zoonotic circulation in this mid-term recovery phase, until forest is fully restored [5]. Acknowledgements: the authors acknowledge the partial support of National Biodiversity Future Centre (NBFC-PNRR) funded by the Italian Ministry of University and Research. This project was partially funded by the EU project BEPREP (https://www.beprep-project.eu/) (GA101060568). Camera traps were kindly provided by Unione Nazionale Cacciatori Zona Alpi (UNCZA).