Territorial animals carry out extra-territorial movements (forays) to obtain pre-dispersal information or to increase reproductive success via extra-pair copulation. However, little is known about ...other purposes and spatial movement patterns of forays. In this study, we GPS-tagged 54 Eurasian beavers (Castor fiber), a year-round territorial, monogamous mammal, during the non-mating season. We investigated forays in territory-holding breeders (dominants) and non-breeding (subordinate) family members. Twenty of 46 dominant individuals (44%), and 6 of 10 subordinates (60%) conducted forays. Generally, beavers spent between 0 and 11% of their active time on forays, travelled faster and spend more time in water when on forays compared to intra-territorial movements, suggesting that forays are energetically costly. Further, beavers in smaller territories conducted more forays. Possibly, smaller territories might not have sufficient resources and thus dominant individuals might conduct forays to assess possibilities for territory expansion, and potentially for foraging. Generally, besides territory advertisement (e.g. via scent-marking), forays might serve as an additional mechanism for territory owners to assess neighbours. Subordinates spent more time on forays, moved greater distances and intruded into more territories than dominant individuals did, suggesting that they prospected to gain information on the population density and available mates before dispersal.
In this study, we describe the dental remains of a very minute beaver from the early Late Miocene locality Hammerschmiede (MN 7/8) located at the Northern Alpine Foreland Basin (Southern Germany, ...Bavaria). The finds represent the so far most comprehensive (>1.000 dental specimens) collection of the trogontheriine castorid Euroxenomys minutus. Metrically and morphologically, the large data set demonstrates an extensive intraspecific variability of this beaver from Hammerschmiede that covers most finds of other European localities and confirms previous species assignments. The subspecies Euroxenomys minutus rhenanus from Dorn-Dürkheim (Germany), clearly isolates from this range of variation and can thus be validated. The performed age-frequency distributions for Euroxenomys minutus from the local stratigraphic levels HAM 5 (rivulet) and HAM 4 (river) correspond roughly and also resemble Euroxenomys from the swamp deposit Rudabánya (Hungary). Since previous mortality studies on the also occurring larger beaver Steneofiber depereti from Hammerschmiede demonstrated dominance of behavioural or internal factors, this cross-ecosystem similarity in mortality for the small beaver species is likely explained by external factors, such as predation. Supported by a taphonomic bone analysis, a multitude of predators are finally considered to prey on Euroxenomys minutus and indicate a predatory bone assemblage.
Poor condition of many streams and concerns about future droughts in the arid and semi-arid western USA have motivated novel restoration strategies aimed at accelerating recovery and increasing water ...resources. Translocation of beavers into formerly occupied habitats, restoration activities encouraging beaver recolonization, and instream structures mimicking the effects of beaver dams are restoration alternatives that have recently gained popularity because of their potential socioeconomic and ecological benefits. However, beaver dams and dam-like structures also harbor a history of social conflict. Hence, we identified a need to assess the use of beaver-related restoration projects in western rangelands to increase awareness and accountability, and identify gaps in scientific knowledge. We inventoried 97 projects implemented by 32 organizations, most in the last 10 years. We found that beaver-related stream restoration projects undertaken mostly involved the relocation of nuisance beavers. The most common goal was to store water, either with beaver dams or artificial structures. Beavers were often moved without regard to genetics, disease, or potential conflicts with nearby landowners. Few projects included post-implementation monitoring or planned for longer term issues, such as what happens when beavers abandon a site or when beaver dams or structures breach. Human dimensions were rarely considered and water rights and other issues were mostly unresolved or addressed through ad-hoc agreements. We conclude that the practice and implementation of beaver-related restoration has outpaced research on its efficacy and best practices. Further scientific research is necessary, especially research that informs the establishment of clear guidelines for best practices.
In November 2016, the Scottish Government announced that they were minded to allow the two 'trial' reintroduced populations of Eurasian beaver Castor fiber to remain in Scotland and be allowed to ...expand naturally, and that the species will receive legal protection. This was a historic moment: the first formally approved reintroduction of a mammal species anywhere in the United Kingdom.
The issues surrounding beaver reintroduction to Scotland had been the subject of intense investigation and public debate over the previous 21 years. Extensive multidisciplinary and interdisciplinary work was performed to assess the desirability and feasibility of reintroducing the Eurasian beaver and informed the government's decision. This was one of the most detailed assessments carried out for any species reintroduction proposal.
The work was broadly divided into desk‐based and stand‐alone studies based primarily on the European and North American experience of living with beavers, the scientifically monitored Scottish Beaver Trial reintroduction in west Scotland, a study of beavers resulting from unauthorised releases in an east Scotland catchment and the work of a specialist group that examined beaver–salmonid interactions and issues.
It was confirmed that beavers have a very positive influence on biodiversity overall, although some specific species and habitats of high conservation importance can be adversely affected if appropriate management is not in place. Beavers provide a range of ecosystem services with the potential for socio‐economic benefits. However, beavers' activities may affect some land uses, the extent and significance depending on local conditions. Management techniques are well developed, although some will require refinement and appropriate licensing within a Scottish regulatory regime. A strategic approach to developing management throughout Scotland will need to be progressed in partnership with key stakeholders.
Across Eurasia and North America, beaver (Castor spp), their dams and their human-built analogues are becoming increasingly common restoration tools to facilitate recovery of streams and wetlands, ...providing a natural and cost-effective means of restoring dynamic fluvial ecosystems. Although the use of beaver ponds by numerous fish and wildlife species is well documented, debate continues as to the benefits of beaver dams, primarily because dams are perceived as barriers to fish movement, particularly migratory species such as salmonids. In this study, through a series of field experiments, we tested the ability of juvenile salmonids to cross constructed beaver dams (aka beaver dam analogues). Two species, coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss), were tracked using passive integrated transponder tags (PIT tags) as they crossed constructed beaver dam analogues. We found that when we tagged and moved these fishes from immediately upstream of the dams to immediately downstream of them, most were detected upstream within 36 hours of displacement. By the end of a 21-day field experiment, 91% of the displaced juvenile coho and 54% of the juvenile steelhead trout were detected on antennas upstream of the dams. In contrast, during the final week of the 21-day experiment, just 1 of 158 coho salmon and 6 of 40 (15%) of the steelhead trout were still detected on antennas in the release pool below the dams. A similar but shorter 4-day pilot experiment with only steelhead trout produced similar results. In contrast, in a non-displacement experiment, juveniles of both species that were captured, tagged and released in a pool 50 m below the dams showed little inclination to move upstream. Further, by measuring hydraulic conditions at the major flowpaths over and around the dams, we provide insight into low-flow conditions under which juvenile salmonids are able to cross these constructed beaver dams, and that multiple types of flowpaths may be beneficial towards assisting fish movement past instream restoration structures. Finally, we compared estimates of the number of juvenile salmonids using the pond habitat upstream of the dam relative to the number that the dam may have prevented from moving upstream. Upstream of the dams we found an abundance of juvenile salmonids and a several orders of magnitude difference in favor of the number of juveniles using the pond habitat upstream of the dam. In sum, our study suggests beaver dams, BDAs, and other channel spanning habitat features should be preserved and restored rather than removed as perceived obstructions to fish passage.
The Middle Pleistocene – Late Pleistocene transition of European large mammal's fauna (Proboscidea, Artiodactyla, Perissodactyla, Carnivora, Hystrix and Castor) assemblages has been studied in 18 ...European regional faunal assemblages. This study is based on the data yielded from 423 palaeontological sites (758 localities) dated within interval of MIS 6–MIS 4. All the data was aggregated by 9 time intervals (time scale). For ten bioregions, we have been able to obtain descriptive models of evolution of their faunal assemblages. It allowed detecting common rules of changes in large mammals' fauna composition in Europe on the whole as well as changes in the distribution of individual species and their groups within the regions. We have studied the changes in biodiversity parameters (Shannon index, index of self-organization) and Mourelle–Ezcurra species turnover index within MIS 6–MIS 4 time interval. The evolution of European fauna was compared for MIS 6–MIS 5 transition and MIS 2–MIS 1 transition as well as influence of change in global temperature on these transitions was described. In addition, we have showed the correlation between modern species richness with the species richness in MIS 6, MIS 5 and MIS 4 and proposed the hypothesis of historical succession of European bioregions.
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Beavers are starting to colonize low arctic tundra regions in Alaska and Canada, which has implications for surface water changes and ice-rich permafrost degradation. In this study, we assessed the ...spatial and temporal dynamics of beaver dam building in relation to surface water dynamics and thermokarst landforms using sub-meter resolution satellite imagery acquired between 2002 and 2019 for two tundra areas in northwestern Alaska. In a 100 km2 study area near Kotzebue, the number of dams increased markedly from 2 to 98 between 2002 and 2019. In a 430 km2 study area encompassing the entire northern Baldwin Peninsula, the number of dams increased from 94 to 409 between 2010 and 2019, indicating a regional trend. Correlating data on beaver dam numbers with surface water area mapped for 12 individual years between 2002 and 2019 for the Kotzebue study area showed a significant positive correlation (R2 = 0.61; p < .003). Beaver-influenced waterbodies accounted for two-thirds of the 8.3% increase in total surface water area in the Kotzebue study area during the 17 year period. Beavers specifically targeted thermokarst landforms in their dam building activities. Flooding of drained thermokarst lake basins accounted for 68% of beaver-influenced surface water increases, damming of lake outlets accounted for 26%, and damming of beaded streams accounted for 6%. Surface water increases resulting from beaver dam building likely exacerbated permafrost degradation in the region, but dam failure also factored into the drainage of several thermokarst lakes in the northern Baldwin Peninsula study region, which could promote local permafrost aggradation in freshly exposed lake sediments. Our findings highlight that beaver-driven ecosystem engineering must be carefully considered when accounting for changes occurring in some permafrost regions, and in particular, regional surface water dynamics in low Arctic and Boreal landscapes.
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