The impacts of beaver-modified habitats on small mammal populations in Southern Finland in the context of ecological succession

Details

Supervisors

Janne Sundell ; Petri Nummi ; Schtickzelle, Nicolas

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

Beavers are widely known as ecological engineers, shaping their environment and facilitating many other species, both plant and animal, to thrive. By physically modifying their environment, they induce biological changes and create heterogeneity within the ecosystem. The beaver's impact remains visible even after it has left the dam. Once the flooding has subsided, the site becomes an open meadow, giving way to ecological succession. Several studies have been carried out on the impact of beavers on small mammal populations during their presence. However, very few studies have been carried out on the impact of the habitat modified by beavers on these species in the context of ecological succession. This study was carried out in the Evo Recreation Park in southern Finland. More specifically, three categories of study sites were considered. Five unimpacted control sites, five sites in the early stages of ecological succession and five sites in a more advanced state of ecological succession since the departure of the beavers. At each site, small mammals were counted using snap traps, along with vegetation and dead wood. No significant differences were found between the different stages of succession. Despite the non-significant results of the study, certain trends could be identified. The results suggest that sites recently impacted by beavers support a greater diversity of plant species and small mammals and are slightly more favourable sites for species such as the bank vole (Myodes glareolus) and the field vole (Microtus agrestis). However, it seemed that sites in a more advanced state of succession are less favourable to the species present, as their physical condition was found to be poorer. These results are in line with the literature. On the one hand, the abundance of small mammals decreases with the advancement of ecological succession and, on the other hand, the positive impacts of the beaver are mainly noticeable at the landscape scale rather than at the patch scale. Beavers have little or no impact on alpha diversity, but they do have a significant positive impact on gamma diversity over time and space, since they increase landscape connectivity and heterogeneity, thereby facilitating the movement of many species. This study suggests a broader and longer-term study of small mammal populations impacted by beavers. More generally, the beaver is a very important conservation tool for freshwater habitats that are heavily impacted by humans, as well as for all the living species associated with them.