The return of Eurasian beaver (Castor fiber) to large areas of Europe represents a conservation success with the current population estimated to be around 1.2 million individuals. Their reintroduction to many areas, including Great Britain, has in some cases been controversial. Despite numerous documented benefits to biodiversity, concerns relate to localised flooding, adverse impacts on land use and engineered structures (e.g. culvert blockage), disease transfer, and the influence of beaver habitat modifications on fisheries, particularly in relation to salmonids. This study investigated the impacts of a series of four beaver dams on the upstream movement of brown trout during the spawning period (October-December) at a field site in Scotland. The study site comprised two streams entering a common loch, one modified by a series of four beaver dams, the other remaining unaltered during the Study Period. Trout were captured using electric fishing, fyke nets and rod and line and were tagged with Passive Integrated Transponders (PIT) before release. PIT telemetry antennas were installed below and above each dam to establish successful passage of trout during the monitoring period that included trout spawning movements in 2015 (high flows) and 2016 (low flow). There was a distinct difference in passage success between years, with high flows (using prior rainfall as a proxy measure) and larger fish size being important positive predictors of upstream passage success. A combination of environmental (prior rainfall and water temperature) and biotic (fish size) factors influenced passage success with high flows being a significant covariate at all four dams in two models used to define trout passage dynamics (Weibull and exponential base models), providing the best explanatory variable for fish passage at two of the four dams. Survival analysis and associated modelling indicated that migratory delay was inversely related to previous passage success, whilst motivation was also a determinant of success, with greatest passage in highly motivated trout. Our findings indicate that given the right environmental and biotic factors, brown trout are adept at passing beaver dams, although under certain conditions, beaver dams can impede the movement of brown trout and the magnitude of impact is influenced by these factors. In particular, the barrier effects of beaver dams are exacerbated under low flow conditions, and this may become a greater challenge in the future due to shifting climatic conditions if periods of warmer and drier weather persist and coincide with peak migratory movements of fish.

After centuries of widespread extinction, the Eurasian beaver Castor fiber has recolonised most of its former extent of occurrence, following international and national protection laws, reintroduction programmes, and unauthorized releases. Beavers provide valuable ecosystem services and multiple benefits to native biodiversity, though their activity may trigger conflicts with humans, especially in highly modified landscapes. Therefore, it is important to monitor their range-expansion, particularly at the early stages of the colonization process. This study quantifies beaver presence in Central and Northern Italy, where reproduction was first detected in recent years after five centuries of absence. A mix of techniques including both direct and indirect signs of presence was adopted to assess the occurrence and status of beavers in the area, retrieving data for the application of density estimators and, thus, population estimates. We document that at least 16 reproductive events occurred between 2021 and early 2023, with at least 55 areas of activity, located across three rivers of Central Italy, corresponding to a minimum of 40 individuals. Seven to ten individuals (in at least 5 areas of activity) were also recorded in Northern regions, in continuity with the populations occurring in neighboring countries beyond the Alps. Given the fast range expansion by the species and the potential for conflict with human activities, alongside the efficiency and applicability of our approach, this type of beaver field survey should be adopted by wildlife managers and policy makers both in areas of established presence but also in potential expansion areas, to develop management plans and to figure out opportunities this returning native species may bring.

According to the IUCN guidelines, wildlife reintroduction should consider any impacts on humans within feasibility assessments. Eurasian beavers Castor fiber are recovering across their native range, due to protection laws and reintroductions. In Central Italy, a self-sustaining, naturalised population of Eurasian beavers has been identified in the last five years. A questionnaire to measure whether and how citizens in the local area perceive the presence of the beaver was administered to 1114 respondents. We observed a comprehensive awareness of the presence of the beaver in Italy and a high ability to distinguish it from non-native coypus Myocastor coypus (92.3%). We also recorded a general high knowledge of issues related to the presence of the beaver (i.e., potential effects on indigenous biodiversity). The majority (65.5%) of the surveyed population was in favour of reintroducing the beaver in Central Italy, and only 1.2% was firmly against it. The majority of interviewed people was against the removal of beavers from Central Italy (65.8%), whereas only 3.7% was in favor, citing fears of perceived impacts on the river, crops, and fish populations.

Globally, freshwaters are the most degraded and threatened of all ecosystems. In northern temperate regions, beaver (Castor spp.) reintroductions are increasingly used as a low-cost and self-sustaining means to restore river corridors. River modifications by beavers can increase availability of suitable habitat for fish, including salmonids. This study investigated the response of a population of brown trout (Salmo trutta) to reintroduced Eurasian beaver (Castor fiber) habitat modifications in northern Scotland. The field site comprised two streams entering a common loch; one modified by beavers, the other unaltered. Electrofishing and PIT telemetry surveys indicated abundance of post-young-of-the-year (post-YOY) trout was higher in the modified stream. Considering juvenile year groups (YOY and post-YOY) combined, abundance and density varied with year and season. In the modified stream, fork length and mass were greater, there was a greater variety of age classes, and mean growth was positive during all seasons. Beavers had profound effects on the local brown trout population that promoted higher abundances of larger size classes. This study provides important insight into the possible future effect of beavers on freshwater ecosystems.

In Scandinavia, an increased red fox Vulpes vulpes density during the last decades has been suggested to be caused by direct and indirect human influences on food availability. Recently, attention has been focused on the role of increasing scavenging opportunities due to intensified hunting of ungulates and the reestablishment of large carnivores. In our study, we investigated seasonal and annual variations in diet composition of red fox in Varaldskogen, SE Norway, an area with cyclic voles and a high density of moose Alces alces . Analyses of scats revealed significant differences among seasons in the occurrence of ungulates—mainly moose—and ungulates were the dominating food category during winter (44.9 % of all remains). Snow tracking of red fox (71 km) in winter confirmed the importance of ungulate carcasses, i.e. one case of scavenging per 3 km. The proportions of voles were high during all seasons (11.2–28.8 %); in spite of variation in available abundances, no significant seasonal or annual differences were detected. Other food categories with seasonal variation were birds, berries/seeds and amphibians/reptiles, all more common in snow-free seasons. Our study underlines the importance of ungulate remains during periods when the abundance and diversity of alternative food sources is low. Increased and stabilized populations of red foxes—mediated through remains from hunting and wolf kills from high moose populations—might have an important effect on the population dynamics of small game. Hence, we recommend that this relationship be given attention in future studies.