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Beavers, Castor canadensis in North America and Castor fiber in Eurasia, are widely referred to as nature's engineers due to their ability to rapidly transform diverse landscapes into dynamic wetland ecosystems. Few other organisms exhibit the same level of control over local geomorphic, hydrologic, and ecological conditions. Though freshwater ecosystems are particularly vulnerable to changing climate, beavers and their wetland homes have persisted throughout the Northern Hemisphere during numerous prior periods of climatic change. Some research suggests that the need to create stable, climate-buffered habitats at high latitudes during the Miocene directly led to the evolution of dam construction. As we follow an unprecedented trajectory of anthropogenic warming, we have the unique opportunity to describe how beaver ecosystem engineering ameliorates climate change today. Here, we review how beavers create and maintain local hydroclimatic stability and influence larger-scale biophysical ecosystem processes in the context of past, present, and future climate change. [ABSTRACT FROM AUTHOR]

We evaluated the post‐fire sediment dynamics in beaver ponds to examine these ponds' contributions to sediment storage following disturbance. Beaver dams and beaver mimicry structures impound water and sediment, a function that is of growing interest in wildfire‐prone landscapes. Wildfires typically lead to high sediment loading into rivers in the years following fire, constituting a disturbance to aquatic ecosystems and a challenge to water resource managers. Previous work establishes that beaver dams trap substantial volumes of sediment, but sedimentation appears spatially and temporally heterogeneous and it remains unclear the extent to which short‐term pulses of sediment are attenuated by these structures. We examine the conditions under which beaver dams and beaver mimicry structures store post‐fire sediment by quantifying the sediment volume of 40 ponds, about half of which were burned in large wildfires in the Colorado and Wyoming Rocky Mountains in 2020. The median relative volume of burned ponds is 85%, which is greater than the median for unburned ponds (58%), meaning that burned ponds store higher relative volumes of sediment when pond size is accounted for. Furthermore, sediment accumulated at a median rate of 3.0 cm/year over the entire history of the pond. Post‐fire sedimentation rates, with a median of 20.4 cm/year, were an order of magnitude higher than pre‐fire rates with a median of 1.8 cm/year. In addition, vegetation and geomorphic characteristics correlated with sediment storage in ponds. Sediment surveys confirmed that ponds with greater surface areas contain higher volumes of sediment. Additionally, older ponds and ponds abandoned by beavers stored higher volumes of sediment compared to recently constructed ponds, ponds actively maintained by beaver, and beaver mimicry structures. These findings demonstrate that beaver ponds and mimicry structures may function as sediment sinks capable of attenuating post‐fire sediment. The biogeomorphic context, defined across multiple scales from the pond to the catchment, provides additional explanation for the wide range of sediment storage observed and remains an important consideration for beaver‐based restoration, catchment sediment management, and resilience evaluation. [ABSTRACT FROM AUTHOR]

Context. The North American beaver (Castor canadensis) was extirpated from much of its range in the US in the 1800s due to fur trapping and change in land use. However, the species has recolonised much of its former range, including the US state of Ohio. Since 2013, the Ohio Division of Wildlife (ODOW) has monitored trends in beaver colony density via aerial surveys of 40 km × 40 km plots classified as low, medium, or high suitability based on the amount of wetland. Nonetheless, the current classification system may miss important correlates of beaver colony density. Aims. Our study aimed to (1) identify predictors of beaver colony density (number of colonies inferred from aerial counts of lodges) across Ohio, and (2) develop a model-based classification system to improve the efficacy of monitoring efforts. Methods. To predict beaver colony density in Ohio we used an aerial survey dataset of 54 plots (40 km × 40 km) collected by ODOW annually between 2013 and 2020, along with a suite of environmental, anthropogenic, and climate variables in a mixed effects modelling framework. Key results. Beaver colony density was positively associated with wetland and reclaimed surface mine areas and inversely associated with the proportion of agricultural lands. There was a negative interaction between wetland and surface mines; in general, beaver colony density increased with wetland and surface mine area. However, in plots with wetland area >1000 ha, beaver colony density was weakly negatively associated with surface mine area. Using median and interquartile ranges of model-averaged predicted beaver colony density, we developed a new classification of low, moderate and high suitability for both the survey plots and the entire state of Ohio. We found that eastern Ohio had high suitability, while the central and western parts of the state had lower suitability for C. canadensis. Conclusions. Our approach to identifying predictors for beaver colony density at broad spatial scales highlights the importance of reclaimed surface mines and wetlands for beaver populations, while the model-based habitat classification provides ODOW additional information for monitoring and beaver management decisions. Implications. Improved C. canadensis monitoring at the landscape scale using habitat classifications that consider local conditions can both improve annual survey cost-effectiveness and facilitate the sustainable management of this recovering species. [ABSTRACT FROM AUTHOR]

Our post-project monitoring research focuses on a natural beaver dam on French Creek in the Scott River Watershed in Siskiyou County, CA. The dam exists on a stretch of the creek with several beaver dam analogues (BDAs), which have been implemented by the Scott River Watershed Council in the hopes of combatting incision in the system and recruiting beaver to maintain the structures. French Creek in particular is an important spawning ground for the threatened coho salmon, so the impacts of the dam on fine sediment are of particular interest. Since the installment of the BDAs on French Creek, a beaver family has colonized the site and built a natural beaver dam. In 2021, high flows led to a breach in this dam. Scott River Watershed Council (Council) developed plans to fortify it using similar techniques used in the nearby BDAs. These plans will be implemented in November 2023, one week after this survey.This dam breach presented the unique opportunity to analyze the surrounding area before its reconstruction, providing both post-breach and pre-reconstruction information on beaver presence, groundwater levels, channel morphology, and sediment grain size. We found evidence of continued beaver activity at the site. Groundwater levels were lower compared to pre-breach data from 2020. Sediment grain size was bimodal directly below the breached dam as compared to an upstream site with imported gravels, potentially indicating a release of fine sediment during the breach. Given the impact of fine sediment on salmon spawning, these fluxes of sediment should be carefully studied and managed. Comparable cross-section data did not exist for the studied reach, so we cannot draw conclusions about the impact of the breach on these metrics, though they may be used going forward to assess the influence of the artificial dam repair.

Vegetation restoration projects throughout the American Southwest have yielded positive outcomes for degraded desert streams, including the Mojave River restoration at Afton Canyon in the Eastern Mojave Desert (Egan, 1999; 2016; Bunn et al., 2003). Although rare, beaver translocation has demonstrated success as a passive desert river restoration strategy at the Price and San Rafael Rivers in eastern Utah and the San Pedro River in Arizona (Soykan et al., 2009; Doden, 2021; Sandbach, 2023). The success of translocated beaver populations is determined by mortality rate and site fidelity, as dictated by habitat quality (Colleen & Gibson, 2000; McKinstry & Anderson, 2002; Petro et al., 2015; Morris et al., 2021; Bilby & Moseby, 2023). In deserts, beaver habitat is restricted to riparian forests (Rutherford, 1964; Bee et al., 1981; Welch et al., 1993). The restoration project at Afton Canyon has facilitated the return of native willow and cottonwood populations and beaver sightings have increased (Egan, 1999; 2016; MDRCD, 2022). It is likely that a combination of natural beaver recolonization and translocation would facilitate further habitat restoration.

Abstract The range of keystone species is increasing in some parts of the world, particularly Europe, through a combination of natural recolonization, government‐sanctioned and covert reintroductions. Reintroductions are an important conservation tool, particularly in the increasingly popular approach of rewilding. There is relatively little understanding of the politics, broadly conceived, of species reintroduction, particularly around how people who live alongside these newly introduced species might react, and what underpins this reaction, and how the method of reintroduction affects reactions. Here, we explore these issues through a case of beavers in central Scotland, which were covertly reintroduced. We explore opposition to reintroduction as manifest in beaver killing and dam destruction by land managers, quantifying these using the sensitive ‘bean count’ method. We also explore what underpins land managers' reactions, particularly their views and values around land and land management. We found considerable resistance. We found that beaver killing and dam destruction were widespread, both before and after beavers became a protected species. Nevertheless, beaver populations and ranges in Scotland continue to grow. We found attitudes were grounded in a strong set of relational values around land custodianship. We find a range of views towards beavers, including widespread opposition, particularly regarding the covert nature of beaver introduction, the challenge beavers and beaver protection provide to ideas of proper land management and custodianship, and a lack of trust in formal methods of beaver governance. We argue that species reintroductions policies and research should give careful consideration to potential opposition, its material impacts on reintroduction projects and how it is grounded in wider environmental values and politics. Read the free Plain Language Summary for this article on the Journal blog.

The results of a 20-year monitoring of beavers (Castor fiber) in the eastern part of the Polistovo-Lovatskaya bog system are presented. The animal's and settlements spatial distributions across different types of water bodies are discussed, and the population density and the impact of beavers on the vegetation of the bog system on the northern and eastern borders of the Rdeysky State Nature Reserve are presented. The forecast of long-term dynamics of the beaver population indicates the maximum possible capacity of the environment in the Rdeysky Nature Reserve. Model estimates indicate that beavers will remain a permanent component of ecosystems for at least the next 200 years; hence, their impact on different components of ecosystems will continue. [ABSTRACT FROM AUTHOR]

The range of keystone species is increasing in some parts of the world, particularly Europe, through a combination of natural recolonization, government‐sanctioned and covert reintroductions. Reintroductions are an important conservation tool, particularly in the increasingly popular approach of rewilding.There is relatively little understanding of the politics, broadly conceived, of species reintroduction, particularly around how people who live alongside these newly introduced species might react, and what underpins this reaction, and how the method of reintroduction affects reactions.Here, we explore these issues through a case of beavers in central Scotland, which were covertly reintroduced. We explore opposition to reintroduction as manifest in beaver killing and dam destruction by land managers, quantifying these using the sensitive 'bean count' method.We also explore what underpins land managers' reactions, particularly their views and values around land and land management.We found considerable resistance. We found that beaver killing and dam destruction were widespread, both before and after beavers became a protected species. Nevertheless, beaver populations and ranges in Scotland continue to grow.We found attitudes were grounded in a strong set of relational values around land custodianship. We find a range of views towards beavers, including widespread opposition, particularly regarding the covert nature of beaver introduction, the challenge beavers and beaver protection provide to ideas of proper land management and custodianship, and a lack of trust in formal methods of beaver governance.We argue that species reintroductions policies and research should give careful consideration to potential opposition, its material impacts on reintroduction projects and how it is grounded in wider environmental values and politics. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Scientists and policy‐makers promote 'Nature‐based Solutions' to the interconnected challenges associated with the Anthropocene. Often these involve the strategic use of ecosystem engineers: animals, plants, and microbes with disproportionate ecological agency capable of regional or even planetary‐scale niche construction. This environmental mode of biopolitics is promoted as biomimicry: restoring, rewilding, or rewetting diverse ecological systems. This paper critically examines the multispecies relations promised by this model through a focus on beaver in Britain over the last 12,000 years. It begins with beaver making Britain hospitable for early settlers and agriculturalists as they returned after the last ice age. It traces the subsequent demise of beaver due to hunting and land use change, and then follows the recent return of beaver as tools for natural flood management and nature recovery. It attends to situations in which these multispecies world‐making projects go awry in the weird ecologies of the Anthropocene. This story of beaver helps situate enthusiasms for proactive ecosystem engineering in deeper time. It highlights the beguiling potential of Nature‐based Solutions while cautioning against tendencies towards anthropocentrism, an apolitical mononaturalism, and an ecomodernist hubris. The paper combines concepts from archaeology, ecology, anthropology, and geography into a new framework for theorising multispecies acts of worlding and weirding. [ABSTRACT FROM AUTHOR]

This study evaluated the chemical, physical and sensory properties of canned beaver and nutria. These animals are currently hunted not for their meat, but to reduce their numbers in the wild. The situation is complicated by the fact that both species are on the relevant lists. However, while the beaver is a protected animal, the nutria is an invasive species. This leads to complications in the application of the relevant legislation. Hunters are therefore limited in what they can do with the meat of these species. The chemical composition of the products did not differ (p > 0.05). Canned beaver was the darkest (p < 0.05) product and canned nutria the softest (p < 0.05). Both meat products were sensory acceptable and no off-odour or off-flavour was perceived. Canning meat is something that hunters can easily do at home, and the resulting product meets all the requirements for food safety. [ABSTRACT FROM AUTHOR]

There is a need to fully know the physiology of Eurasian beaver due to its essential role in environmental homeostasis. However, a "human factor" impacts this, including stress conditions and environmental pollution. Adrenal glands protect these all. The regulation of endocrine processes by nonclassical androgen and estrogen signaling, the first and fastest control, is still a matter of research. The specific analyses performed here in mature female and male beaver adrenals contained: anatomical and histological examinations, expression and localization of membrane androgen receptor (zinc transporter, Zinc‐ and Iron‐like protein 9; ZIP9) and membrane estrogen receptor coupled with G protein (GPER), and measurement of zinc (Zn2+) and copper (Ca2+) ion levels and corticosterone levels. We revealed normal anatomical localization, size, and tissue histology in female and male beavers, respectively. Equally, ZIP9 and GPER were localized in the membrane of all adrenal cortex cells. The protein expression of these receptors was higher (p < 0.001) in male than female adrenal cortex cells. Similarly, Zn2+ and Ca2+ ion levels were higher (p < 0.05, p < 0.01) in male than female adrenal cortex. The increased corticosterone levels (p < 0.001) were detected in the adrenal cortex of females when compared to males. The present study is the first to report the presence of nonclassical androgen and estrogen signaling and its possible regulatory function in the adrenal cortex of Eurasian beavers. We assume that this first‐activated and fast‐transmitted regulation can be important in the context of the effect of environmental physical and chemical stressors especially on adrenal cortex cells. The beaver adrenals may constitute an additional supplementary model for searching for universal mechanisms of adrenal cortex physiology and diseases. Highlights: There are no sex‐specific changes in the anatomy and histology of Eurasian beavers.Expression of ZIP9 and GPER is higher in males.Zn2+ and Ca2+ levels were higher in males.The corticosterone levels are higher in females. [ABSTRACT FROM AUTHOR]

Dam building by beaver (Castor spp.) slows water movement through montane valleys, increasing transient water storage and the diversity of residence times. In some cases, water storage created by beaver dam construction is correlated to changes in streamflow magnitude and timing. However, the total amount of additional surface and groundwater storage that beaver dams may create (and, thus, their maximum potential impact on streamflow) has not been contextualized in the water balance of larger river basins. We estimate the potential transient water storage increases that could be created at 5, 25, 50, and 100% of maximum modeled beaver dam capacity in the Bear River basin, USA, by adapting the height above nearest drainage (HAND) algorithm to spatially estimate surface water storage. Surface water storage estimates were combined with the MODFLOW groundwater model to estimate potential increases in groundwater storage throughout the basin. We tested four scenarios to estimate potential transient water storage increases resulting from the construction of 1179 to 34,897 beaver dams, and estimated surface water storage to range from 57.5 to 72.8 m3 per dam and groundwater storage to range from 182.2 to 313.3 m3 per dam. Overall, we estimate that beaver dam construction could increase transient water storage by up to 10.38 million m3 in the Bear River basin. We further contextualize beaver dam-related water storage increases with streamflow, reservoir, and snowpack volumes. [ABSTRACT FROM AUTHOR]

Areas excluded from agricultural production are susceptible to the presence of beaver families. The most significant changes occur during the initial period, when agricultural utilization is abandoned and beavers establish their presence on the land. During this period, some parcels remain uncultivated, while agricultural activities persist in neighboring areas. This situation is accompanied by the destruction of beaver dams, especially during periods of abundant water resources, and notably during intensive fieldwork. The article presents field studies aimed at determining the extent to which constructed and operational beaver dams contribute to changes in groundwater levels in drained peatland areas. In order to protect and sustainably use peat soils, it is necessary to maintain their high moisture content by ensuring a high groundwater level elevation. This can be achieved through the use of existing damming structures in the area (levees, weirs). Beaver dams can also serve a similar function, blocking the outflow of water from peat lands by raising the water level and consequently retaining it naturally. The specific objective was to develop principles for verifying factors influencing the effects of beaver dam construction on groundwater levels in fields within their range of influence. The water table levels within the study area during rainless periods were influenced by water levels in ditches, dependent on beaver activity in the nearby river. Beaver activities, manifested through dam construction, were influenced by periodic water resources in the river, defined by the cumulative monthly precipitation. Factors affecting groundwater levels in rainless periods on the plots also included the distance from the river cross-section and the permeability of soils expressed by the filtration coefficient of the active layer. Beaver dams had the greatest impact on stabilizing the water table in the soil profile closest to the river. [ABSTRACT FROM AUTHOR]

Stream restoration programs employ beaver‐related restoration techniques, including beaver translocations and installation of beaver dam analogs (BDA), to create complex in‐stream habitat. We investigated whether BDA installations improved the probability of translocated beavers surviving and colonizing a section of a degraded desert river. We translocated beavers fitted with tracking devices to the Price River, Utah, United States, for 2 years before and after BDAs were installed. We monitored survival and site fidelity of beavers to estimate apparent survival (φ), using model selection to evaluate models with BDA, flow, and other factors hypothesized to relate to apparent survival. We found similar apparent survival 8 weeks post‐release of pre‐BDA (φ = 0.50 ± 0.08 SE) and post‐BDA beavers (φ = 0.41 ± 0.06 SE). There were 15 predator‐caused mortalities and 39 beavers emigrated out of the study site. Top models indicated apparent survival was negatively related to mean flow. Of the 70 BDAs constructed, beaver activity was detected on only two structures and the number of intact natural dams decreased due to monsoon floods. Our results suggest BDAs may not improve survival and site fidelity of translocated beavers in desert river systems. Instead, the dynamic flow of desert rivers and negative relationship between flow and apparent survival suggest the timing of release may be an important consideration for successful beaver translocation. Additional research is needed to understand how habitat, food availability, individual behavior, and resident conspecifics influence beaver translocation success. [ABSTRACT FROM AUTHOR]

We report an outbreak of COVID-19 in a beaver farm in Mongolia in 2021. Genomic characterization revealed a unique combination of mutations in the SARS-CoV-2 of the infected beavers. Based on these findings, increased surveillance of farmed beavers should be encouraged.

Borna disease (BD) associated with a peracute bacterial septicaemia with Escherichia coli was diagnosed in an adult female, naturally infected, free-ranging Eurasian beaver of the subspecies Castor fiber albicus , clinically characterized by weight loss, depression, weakness and gurgled peristaltic sounds. The beaver was euthanized humanely. Necropsy and light microscopy revealed a non-purulent meningoencephalitis with typical mononuclear perivascular cuffs and parenchymal infiltrates. The diagnosis of BD was confirmed by detection of viral antigen and RNA by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The PCR product was sequenced and cluster analysis revealed a close relationship between endemic clusters in Saxony-Anhalt. This is the first report of naturally occurring BD in a free-ranging Eurasian beaver. [ABSTRACT FROM AUTHOR]

Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs (Rana pretiosa) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers (Castor canadensis), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture‐mark‐recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture‐mark‐recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought. [ABSTRACT FROM AUTHOR]

We measured the total mercury (THg) concentration in the muscle of northern pike (Esox lucius L.) from 12 boreal headwater lakes once per decade during the 1980s to 2010s. Relations of pike THg to regional environmental changes, such as reduction of acid deposition and increase in water colour (i.e. browning), were examined as well as the effects of local lake-specific changes caused by introduced beavers (Castor canadensis) and intensive fishing of pike. No consistent decrease in pike THg took place during 1983–2013 despite the reductions in mercury emissions from European sources since the 1990s and the associated decreased mercury deposition in Finland. In most of the lakes, individual pike exceeded the recommended limit for human consumption (1 mg kg−1, wet weight). The highest THg levels were recorded in 2002 following intensive browning of the lakes in the 1990s in connection with decreased sulphate deposition. The effects of acid deposition were only seen as the highest pike THg in the two most acidic lakes in the early 1980s. After taking length effects into account, pike THg had a negative relationship with growth (i.e. growth dilution), but a positive relationship with water colour, iron, nutrients and maximum lake depth. Females grew faster and had lower THg than males. Pike THg was elevated in beaver-impacted lakes. Experimental removal of pike from three study lakes during 2005–2013 resulted in a decrease of pike THg. These findings emphasize the significance of local abiotic and biotic drivers when interpreting the regional long-term trends in pike THg. [ABSTRACT FROM AUTHOR]

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Abstract Individual animals are often given names by humans. For example, names are attributed to domestic animals to acknowledge their closeness to people, some research studies use names to identify differences between individuals in a study group, or zoos often use names to tell stories that attract public or media attention. Publicly naming individual animals can provide opportunities in conservation, but there are also risks. In this perspective we exemplify such opportunities and risks in the context of wildlife reintroductions. We draw on examples and observations from our experience researching Eurasian beaver Castor fiber reintroduction in England, to encourage careful thinking before publicly attributing a name to an individual in reintroduction projects. Naming individuals in reintroduction can: be a low‐cost engagement tool; help people relate to unfamiliar reintroduced species; encourage local ownership of reintroduction projects; enable an effective tool for communicating information about the species and ways to coexist; or support creative or cultural expression. Yet naming individuals in reintroduction could: risk misrepresentation of natural species characteristics; make it challenging to normalise the sense that the reintroduced species is a wild animal; unintentionally imply that humans have ownership or power over the animal; cause distraction from establishing viable populations due to focus on the individual; or result in human investment in individual animals, which may have influence on reintroduction outcomes if that animal later comes to harm or dies (naturally or otherwise). Synthesis and Applications. We argue there is more to the act of naming individuals than may first appear. If considering doing so, we call for careful thought about whether it is appropriate and how to go about it. While we intentionally refrain from concluding whether ‘to name or not to name’, we call for careful, informative, message framing that takes advantage of the opportunities and is prepared for future circumstances, when naming of individuals does take place. Read the free Plain Language Summary for this article on the Journal blog.

The story of the Cornwall Beaver Project is presented as the foundation of a review of the literature to consider the effects of beavers on geomorphological and hydrological processes, habitats, biodiversity, and people in agricultural landscapes in the UK. The review includes a comparison of the principles for rewilding as an approach to ecological restoration with IUCNs principles for Nature-based Solutions together with a summary of beaver reintroduction in Europe, and the impacts of beavers on hydrological and geomorphological processes, biodiversity and the human-wildlife conflict that arises from reintroduction. We note that rewilding principles require a paradigm shift in the relationship between humans and the rest of nature and a corresponding application of systems thinking to research, practice and policy. The combination of experiential and formal knowledge is assessed using a social-ecological systems framework to consider the potential of beavers to mitigate climate change impacts on agricultural landscapes in the UK and how rewilders might navigate the social complexity of beaver reintroduction to achieve large scale system transformation. We discuss the different lines of evidence about the impacts of beavers on landscapes as viewed through a system lens and conclude that: (1) beaver dams have considerable potential to store water but their ability to reduce flood risk is difficult to assess because of the complex interactions between the material available for dam construction, geomorphology, and the duration, extent and intensity of rainfall events; (2) beaver dams, especially when combined with buffer zones along water courses have considerable potential to enhance the resilience of agricultural landscapes and support a shift from intensive to agroecological farming; (3) scaling beaver reintroduction will evolve with the application of policies and practices that enhance the ability of land users to adapt and learn how to coexist with beavers. Our review proposes a low conflict strategy for rewilding with beavers that includes changes from a policy of conflict avoidance to a proactive policy to support practices that apply the tools of social-ecological systems science to the body of knowledge about the interactions between beavers and their environment. [ABSTRACT FROM AUTHOR]

The European beaver (Castor fiber) was a fully eradicated species in Slovakia. Thanks to year-round protection and several different reintroduction programs the population is now increasing. However, there are limited reports about their health status. A 2-year-old female European beaver, was found dead by road near town Hanušovce nad Topľou in eastern Slovakia in 2021. Necropsy was carried out at the Department of Breeding and Diseases of the Game, Fish and Bees, Ecology and Cynology, University of Veterinary Medicine and Pharmacy in Košice. Necropsy revealed a total of 13 trematodes, collected from the caecum and colon. Based on morphological and molecular analysis digenean trematode Stichorchis subtriquetrus (Rudolphi, 1814) was identified. This is the first record of adult helminth Stichorchis subtriquetrus in beaver in Slovakia. [ABSTRACT FROM AUTHOR]

The story of the Cornwall Beaver Project is presented as the foundation of a review of the literature to consider the effects of beavers on geomorphological and hydrological processes, habitats, biodiversity, and people in agricultural landscapes in the UK. The review includes a comparison of the principles for rewilding as an approach to ecological restoration with IUCNs principles for Nature-based Solutions together with a summary of beaver reintroduction in Europe, and the impacts of beavers on hydrological and geomorphological processes, biodiversity and the human-wildlife conflict that arises from reintroduction. We note that rewilding principles require a paradigm shift in the relationship between humans and the rest of nature and a corresponding application of systems thinking to research, practice and policy. The combination of experiential and formal knowledge is assessed using a social-ecological systems framework to consider the potential of beavers to mitigate climate change impacts on agricultural landscapes in the UK and how rewilders might navigate the social complexity of beaver reintroduction to achieve large scale system transformation. We discuss the different lines of evidence about the impacts of beavers on landscapes as viewed through a system lens and conclude that: (1) beaver dams have considerable potential to store water but their ability to reduce flood risk is difficult to assess because of the complex interactions between the material available for dam construction, geomorphology, and the duration, extent and intensity of rainfall events; (2) beaver dams, especially when combined with buffer zones along water courses have considerable potential to enhance the resilience of agricultural landscapes and support a shift from intensive to agroecological farming; (3) scaling beaver reintroduction will evolve with the application of policies and practices that enhance the ability of land users to adapt and learn how to coexist with beavers. Our review proposes a low conflict strategy for rewilding with beavers that includes changes from a policy of conflict avoidance to a proactive policy to support practices that apply the tools of social-ecological systems science to the body of knowledge about the interactions between beavers and their environment.

Beaver management requires understanding beaver habitat preferences. Despite the American beaver (Castor canadensis Kuhl, 1820) being relatively common in the upper Midwest region of the United States, there are no beaver habitat relationship models based on this area. We used 1735 colonization events from long-term monitoring data generated by the Chequamegon-Nicolet National Forest in northern Wisconsin, USA, to determine what geomorphological and biological factors were selected by beavers colonizing new sites. We developed and evaluated prediction performance for three colonization models: geomorphology factors only, geomorphology and vegetation factors, and a full colonization model based on geomorphology, vegetation, and availability of dispersing beavers. Overall, the geomorphology–vegetation–colonizer model was the best model, predicting actual colony locations better than the other two models. Spatially, the landscape open to beaver colonization was a mosaic of streams with suitable and unsuitable habitat. These models improve our understanding of how beaver site selection factors in the upper Midwest region differ from factors identified in the literature for the western and eastern United States. This information may be useful for land managers in this region seeking to spatially target resources for restoring northern forest landscapes such as the Chequamegon-Nicolet National Forest. [ABSTRACT FROM AUTHOR]

Wildlife translocation facilitates conservation efforts, including recovering imperiled species, reducing human–wildlife conflict, and restoring degraded ecosystems. Beaver (American, Castor canadensis; Eurasian, C. fiber) translocation may mitigate human–wildlife conflict and facilitate ecosystem restoration. However, few projects measure outcomes of translocations by monitoring beaver postrelease, and translocation to desert streams is relatively rare. We captured, tagged, and monitored 47 American beavers (hereafter, beavers) which we then translocated to two desert rivers in Utah, USA, to assist in passive river restoration. We compared translocated beaver site fidelity, survival, and dam‐building behavior to 24 resident beavers. We observed high apparent survival (i.e., survived and stayed in the study site) for eight weeks postrelease of resident adult beavers (0.88 ± 0.08; standard error) and lower but similar apparent survival rates between resident subadult (0.15 ± 0.15), translocated adult (0.26 ± 0.12), and translocated subadult beavers (0.09 ± 0.08). Neither the pre‐ nor the post‐translocation count of river reaches with beaver dams were predicted well by the Beaver Restoration Assessment Tool, which estimates maximum beaver dam capacity by river reach, suggesting beaver‐related restoration is not maximized in these rivers. Translocated beavers exhibited similar characteristics as resident subadult beavers during dispersal; they were more vulnerable to predation and many emigrated from the study sites. High mortality and low site fidelity should be anticipated when translocating beavers, but even so, translocation may have contributed to additional beaver dams in the restoration sites, which is the common goal of beaver‐assisted river restoration. Multiple releases at targeted restoration sites may eventually result in establishment and meet conservation objectives for desert rivers. [ABSTRACT FROM AUTHOR]

Individual animals are often given names by humans. For example, names are attributed to domestic animals to acknowledge their closeness to people, some research studies use names to identify differences between individuals in a study group, or zoos often use names to tell stories that attract public or media attention.Publicly naming individual animals can provide opportunities in conservation, but there are also risks. In this perspective we exemplify such opportunities and risks in the context of wildlife reintroductions. We draw on examples and observations from our experience researching Eurasian beaver Castor fiber reintroduction in England, to encourage careful thinking before publicly attributing a name to an individual in reintroduction projects.Naming individuals in reintroduction can: be a low‐cost engagement tool; help people relate to unfamiliar reintroduced species; encourage local ownership of reintroduction projects; enable an effective tool for communicating information about the species and ways to coexist; or support creative or cultural expression.Yet naming individuals in reintroduction could: risk misrepresentation of natural species characteristics; make it challenging to normalise the sense that the reintroduced species is a wild animal; unintentionally imply that humans have ownership or power over the animal; cause distraction from establishing viable populations due to focus on the individual; or result in human investment in individual animals, which may have influence on reintroduction outcomes if that animal later comes to harm or dies (naturally or otherwise).Synthesis and Applications. We argue there is more to the act of naming individuals than may first appear. If considering doing so, we call for careful thought about whether it is appropriate and how to go about it. While we intentionally refrain from concluding whether 'to name or not to name', we call for careful, informative, message framing that takes advantage of the opportunities and is prepared for future circumstances, when naming of individuals does take place. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Beavers are ecosystem engineers that create and maintain riparian wetland ecosystems in a variety of ecologic, climatic, and physical settings. Despite the large‐scale implications of ongoing beaver conservation and range expansion, relatively few landscape‐scale studies have been conducted, due in part to the significant time required to manually locate beaver dams at scale. To address this need, we developed EEAGER—an image recognition machine learning model that detects beaver complexes in aerial and satellite imagery. We developed the model in the western United States using 13,344 known beaver dam locations and 56,728 nearby locations without beaver dams. Performance assessment was performed in twelve held out evaluation polygons of known beaver occupancy but previously unmapped dam locations. These polygons represented regions similar to the training data as well as more novel landscape settings. Our model performed well overall (accuracy = 98.5%, recall = 63.03%, precision = 25.83%) in these areas, with stronger performance in regions similar to where the model had been trained. We favored recall over precision, which results in a more complete catalog of beaver dams found but also a higher incidence of false positives to be manually removed during quality control. These results have far‐reaching implications for monitoring of beaver‐based river restoration, as well as potential applications detecting other complex landforms. Plain Language Summary: Beavers are ecosystem engineers that can dramatically change the shape of the landscape and how water moves through it. They create and maintain wetland environments across North America in a wide variety of places, including mountains, deserts, coasts, forests, grasslands, shrublands, etc. Despite their large influence on the landscape, there are very few programs that monitor them at the landscape scale. This is partially due to how much time it takes to find and identify beaver dams in satellite and aerial images. To make it easier for us to find and understand the influence of beavers at larger scales, we built a model that can automatically find beaver dams in satellite and aerial imagery. While our model is trained to find beaver dams, this type of model has promise for finding other landscape features too. Key Points: Tracking the distribution and range of ecosystem engineers like beavers is increasingly important under a changing climateA neural network machine learning model can be trained to find and identify beaver dams in aerial and satellite imagery automaticallyThis type of machine learning model may have applications for finding other landforms where geospatial context is an important input [ABSTRACT FROM AUTHOR]

Studies in boreal regions concerning the bioaccumulative neurotoxin methylmercury (MeHg) in natural wetlands and experimental reservoirs have shown that these waterbodies contribute to high MeHg levels in underlying sediments, inundated vegetation, and aquatic organisms. Beaver ponds are natural reservoirs that are ubiquitous in the Canadian boreal region and have been reported to increase downstream MeHg concentrations. However, the reported impacts of beaver ponds on stream MeHg vary widely across a limited number of studies, and factors influencing this variation are not well understood. To quantify the effect of beaver ponds on stream mercury concentrations, water samples were taken upstream and downstream of 10 in-channel beaver impoundments in northwestern Ontario, Canada. The downstream:upstream MeHg concentration ratios were related to pond and landscape characteristics to examine potential factors that play a role in determining the effect of beaver ponds on stream MeHg concentrations. Overall, MeHg concentrations were 1.6 times greater downstream of the beaver ponds, though this increase was not consistent; downstream concentrations up to 12 times greater and up to 5 times less were also observed. Landscape characteristics that can be readily obtained from existing spatial datasets or quantified using remote sensing techniques emerged as better predictors of downstream:upstream MeHg concentrations than site-specific stream chemistry parameters or pond characteristics that are more difficult to ascertain, with drier landscapes indicative of lower background MeHg export being more likely to exhibit greater increases in MeHg downstream of a beaver pond. These results suggest that the effects of beaver ponds on surface water MeHg concentrations are generally small but highly variable, and that the magnitude of the pond’s influence on stream MeHg are lessened in landscapes already conducive to higher MeHg concentrations.

River to floodplain hydrologic connectivity is strongly enhanced by beaver- (Castor canadensis) engineered channel water diversions. The hydroecological impacts are wide ranging and generally positive, however, the hydrogeochemical characteristics of beaver-induced flowpaths have not been thoroughly examined. Using a suite of complementary ground- and drone-based heat tracing and remote sensing methodology we characterized the physical template of beaver-induced floodplain exchange for two alluvial mountain streams near Crested Butte, Colorado, USA. A flowpath-oriented perspective to water quality sampling allowed characterization of the chemical evolution of channel water diverted through floodplain beaver ponds and ultimately back to the channel in 'beaver pond return flows'. Subsurface return flow seepages were universally suboxic, while ponds and surface return flows showed a range of oxygen concentration due to in-situ photosynthesis and atmospheric mixing. Median concentrations of reduced metals: manganese (Mn), iron (Fe), aluminum (Al), and arsenic (As) were substantially higher along beaver-induced flowpaths than in geologically controlled seepages and upstream main channel locations. The areal footprint of reduced return seepage flowpaths were imaged with surface electromagnetic methods, indicating extensive zones of high-conductivity shallow groundwater flowing back toward the main channels and emerging at relatively warm bank seepage zones observed with infrared. Multiple-depth redox dynamics within one focused seepage zone showed coupled variation over time, likely driven by observed changes in seepage rate that may be controlled by pond stage. High-resolution times series of dissolved Mn and Fe collected downstream of the beaver-impacted reaches demonstrated seasonal dynamics in mixed river metal concentrations. Al time series concentrations showed proportional change to Fe at the smaller stream location, indicating chemically reduced flowpaths were sourcing Al to the channel. Overall our results indicated beaver-induced floodplain exchanges create important, and perhaps dominant, transport pathways for floodplain metals by expanding chemically-reduced zones paired with strong advective exchange.

Wolves (Canis lupus) can exert top‐down pressure and shape ecological communities through the predation of ungulates and beavers (Castor spp.). Therefore, understanding wolf foraging is critical to estimating their ecosystem‐level effects. Specifically, if wolves are consumers that optimize tradeoffs between the cost and benefits of prey acquisition, changes in these factors may lead to prey‐switching or negative‐density dependent selection with potential consequences for community stability. For wolves, factors affecting cost and benefits include prey vulnerability, risk, reward, and availability, which can vary temporally. We described the wolf diet by the frequency of occurrence and percent biomass and characterized the diet using prey remains found in wolf scats on Isle Royale National Park, Michigan, USA, during May–October 2019 and 2020. We used logistic regression to estimate prey consumption over time. We predicted prey with temporal variation in cost (availability and/or vulnerability) such as adult moose (Alces alces), calf moose, and beaver (Castor canadensis) to vary in wolf diets. We analyzed 206 scats and identified 62% of remains as beaver, 26% as moose, and 12% as other species (birds, smaller mammals, and wolves). Adult moose were more likely to occur in wolf scats in May when moose are in poor condition following winter. The occurrence of moose calves peaked during June–mid‐July following birth but before calf vulnerability declined as they matured. By contrast, beaver occurrence in wolf scat did not change over time, reflecting the importance of low‐handling cost prey items for recently introduced lone or paired wolves. Our results demonstrate that the wolf diet is responsive to temporal changes in prey costs. Temporal fluctuation in diet may influence wolves' ecological role if prey respond to increased predation risk by altering foraging or breeding behavior. [ABSTRACT FROM AUTHOR]

Beavers (Castor) stand out among mammals for their unique capacity to fell trees using their large, ever-growing incisors. This routine consumption of resistant fodder induces prodigious wear in the lower incisors, despite this blunting effect the incisors maintain a remarkably sharp cutting edge. Notably, the enamel edges of their incisors show a highly complex two-part microstructure of which the biomechanical import is unknown. Here, using fracture analysis, nanoindentation, and wear testing on North American beaver (C. canadensis) incisors we test the microstructure's possible contribution to maintaining incisal sharpness. Although comparable in hardness, the inner enamel preferentially fails and readily wears at 2.5 times the rate of the outer enamel. The outer microstructure redirects all fractures in parallel, decreasing fracture coalescence. Conversely, the inner microstructure facilitates crack coalescence increasing the wear rate by isolating layers of enamel prisms that readily fragment. Together these two architectures form a microstructurally driven self-sharpening mechanism contained entirely within the thin enamel shell. Our results demonstrate that enamel microstructures exposed at the occlusal surface can markedly influence both enamel crest shape and surface texture in wearing dentitions. The methods introduced here open the door to exploring the biomechanical functionality and evolution of enamel microstructures throughout Mammalia. Enamel microstructure varies significantly with the diversity of diets, bite forces, and tooth shapes exhibited by mammals. However, minimal micromechanical exploration of microstructures outside of humans, leaves our understanding of biomechanical functions in a nascent stage. Using biologically informed mechanical testing, we demonstrate that the complex two-part microstructure that comprises the cutting edge of beaver incisors facilitates self-sharpening of the enamel edge. This previously unrecognized mechanism provides critical maintenance to the shape of the incisal edge ensuring continued functionality despite extreme wear incurred during feeding. More broadly, we show how the architecture of prisms and the surrounding interprismatic matrix dictate the propagation of fractures through enamel fabrics and how the pairing of enamel fabrics can result in biologically advantageous functions. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the distribution of elements (Ca, Mg, Fe, P, Zn, Na, K, Cu, Cr, Mo, Co, Se) analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES) and fluorides (F−) determined potentiometrically using an ion-selective electrode in the enamel of European beaver (Castor fiber) teeth. Material for the study was tooth enamel collected from lower jaws from the skulls of the animals borrowed from museum collections (animals inhabited north-western Poland). The results of our study indicate the important role of F− as an element that can affect the hardness and strength of beaver tooth enamel. Critical to the function of beaver teeth (i.e., shearing and crushing wood) is the presence of elements such as Fe in the central incisor labial aspect (orange layer of the incisor enamel), Mg in the inner side of the incisor enamel, and Co and F− in the enamel of the molars. Thanks to the high content of these elements, the enamel is durable and the teeth are adapted to the nutritional and ecological characteristics of this mammalian species. Our study on the distribution of elements in the enamel of beaver teeth may also be important for the understanding of the enamel mineralization processes, determining how elements change the properties of the materials, and exploring the relationship between the environment and life history of the beaver. [ABSTRACT FROM AUTHOR]

• River restoration has a growing focus on North American beaver (Castor Canadensis). • Beaver-based fixes can harm stream restoration, beaver, and lands and waters. • There are millennia of Indigenous theory about beaver relations in North America. • Settler restorationists can partner with beaver and Native peoples who know beaver. • River restoration must reconnect beaver back to people, place, and time. This Forum brings together river restoration researchers and practitioners to stimulate debate about the recent explosion of interest in North American beaver (Castor canadensis) and beaver-related practices in North American river restoration science and management. While the beaver is described in recent literature as a low-cost, high-impact ecosystem engineer capable of minimizing the impacts of wildfire, drought, flood, and disturbance across the continent, we consider the importance of shifting from a focus on prescriptive results—on what beaver get humans—and towards engaging with beaver in relational process. Through a set of provocations that highlight the potential damage beaver fixes pose for stream restoration, for beaver, and for the lands and waters they inhabit with humans and other beings, we invite settler river scientists, river restorationists, and river thinkers to question the increasingly taken-for-granted logic of beaver as isolated creature, ecosystem engineer, and river savior; defer to the millennia of theory about beaver and their relations on this continent, partnering with beaver and with the Native peoples who have known them longest; and reconnect beaver back to people, place, and time in support of lively, dynamic, diverse, flourishing river systems across the continent. [ABSTRACT FROM AUTHOR]

Abstract Wolves (Canis lupus) can exert top‐down pressure and shape ecological communities through the predation of ungulates and beavers (Castor spp.). Therefore, understanding wolf foraging is critical to estimating their ecosystem‐level effects. Specifically, if wolves are consumers that optimize tradeoffs between the cost and benefits of prey acquisition, changes in these factors may lead to prey‐switching or negative‐density dependent selection with potential consequences for community stability. For wolves, factors affecting cost and benefits include prey vulnerability, risk, reward, and availability, which can vary temporally. We described the wolf diet by the frequency of occurrence and percent biomass and characterized the diet using prey remains found in wolf scats on Isle Royale National Park, Michigan, USA, during May–October 2019 and 2020. We used logistic regression to estimate prey consumption over time. We predicted prey with temporal variation in cost (availability and/or vulnerability) such as adult moose (Alces alces), calf moose, and beaver (Castor canadensis) to vary in wolf diets. We analyzed 206 scats and identified 62% of remains as beaver, 26% as moose, and 12% as other species (birds, smaller mammals, and wolves). Adult moose were more likely to occur in wolf scats in May when moose are in poor condition following winter. The occurrence of moose calves peaked during June–mid‐July following birth but before calf vulnerability declined as they matured. By contrast, beaver occurrence in wolf scat did not change over time, reflecting the importance of low‐handling cost prey items for recently introduced lone or paired wolves. Our results demonstrate that the wolf diet is responsive to temporal changes in prey costs. Temporal fluctuation in diet may influence wolves' ecological role if prey respond to increased predation risk by altering foraging or breeding behavior.

Beavers influence hydrology by constructing woody dams. Using a Before After Control Impact experimental design, we quantified the effects of a beaver dam sequence on the flow regime of a stream in SW England and consider the mechanisms that underpin flow attenuation in beaver wetlands. Rainfall‐driven hydrological events were extracted between 2009 and 2020, for the impacted (n = 612) and control (n = 634) catchments, capturing events 7 years before and 3 years after beaver occupancy, at the impacted site. General additive models were used to describe average hydrograph geometry across all events. After beaver occupancy, Lag times increased by 55.9% in the impacted site and declined by 17.5% in the control catchment. Flow duration curve analysis showed a larger reduction in frequency of high flows, following beaver dam construction, with declines of Q5 exceedance levels of 33% for the impacted catchment and 15% for the control catchment. Using event total rainfall to predict peak flow, five generalized linear models were fitted to test the hypothesis that beaver dams attenuate flow, to a greater degree, with larger storm magnitude. The best performing model showed, with high confidence, that beaver dams attenuated peak flows, with increasing magnitude, up to between 0.5 and 2.5 m3 s−1 for the 94th percentile of event total rainfall; but attenuation beyond the 97th percentile cannot be confidently detected. Increasing flow attenuation, with event magnitude, is attributed to transient floodplain storage in low gradient/profile floodplain valleys that results from an increase in active area of the floodplain. These findings support the assertion that beaver dams attenuate flows. However, with long‐term datasets of extreme hydrological events lacking, it is challenging to predict the effect of beaver dams during extreme events with high precision. Beaver dams will have spatially variable impacts on hydrological processes, requiring further investigation to quantify responses to dams across differing landscapes and scales. [ABSTRACT FROM AUTHOR]

The article presents data on body size and weight of beavers of different ages from Ukraine (Dnipro basin), as well as features of determining the age of males by the size of the baculum and taking into account the bonding lines in the periosteal zone of the mandible. In addition, this paper summarizes the methods for determining the age of the Eurasian beaver, which are used in different countries. Among them are methods that determine the age of beaver by size and body weight, by traces, by craniological features, by the length of the sagittal ridge, by the developmental features and functional state of teeth, by the width of the incisor and the interorbital width of the skull, by the stratification of dentin or cement, and by size and weight of the baculum. The body weight of beavers from Ukraine was 7.0 ± 0.31 (5.5–7.9) kg in individuals of 6–7 months of age, 9.1 ± 0.26 (8.6–9.5) kg in one year old individuals, 12.7 ± 0.30 (11.0–13.9) kg in two years old beavers, 15.6 ± 0.45 (14.4–17.0) kg in individuals of 2.4–3.0 years of age, and 21.8 ± 0.81 (16.2–30.0) kg in beavers over 3.0 years of age. The size of the skull in subsequent age groups was characterized by a significant transgression by the interorbital and zygomatic width of the skull and they clearly differed from one another only by the total length of the skull. Curiously, the mass of the baculum in the Elbe beaver (С. fiber albicus Matschie, 1907) significantly exceeds that of beavers from Ukraine, which may be a results of geographic variation of the animals. In the 1970s, a new method of post-mortem determination of the age of beavers was proposed by studying the polished section of the first molar measuring the height of dentin-enamel loops as well as the thickness of the layer of cement and secondary dentin. It was found that in beavers the cement layer appears in the second year in the lower part of the tooth and, gradually increasing with age, almost completely displaces the dentin-enamel loops by the end of the animal's life. At 3–4 years, secondary dentin appears, which occupies an intermediate position between the cementum and the lower part of the tooth, and, when the latter is chipped, it fills certain areas of its occlusal surface. In addition, there is a method of classification of beavers by age groups (up to 1 year, 1–3 years, over 3 years) based on measuring the radii of the external and internal curvature of the incisors. Depending on the age of the animals, all methods allow to obtain fairly accurate results.

Rivers and streams, when fully connected to their floodplains, are naturally resilient systems that are increasingly part of the conversation on nature‐based climate solutions. Reconnecting waterways to their floodplains improves water quality and quantity, supports biodiversity and sensitive species conservation, increases flood, drought and fire resiliency, and bolsters carbon sequestration. But, while the importance of river restoration is clear, beaver‐based restoration—for example, strategic coexistence, relocation, and mimicry—remains an underutilized strategy despite ample data demonstrating its efficacy. Climate‐driven disturbances are actively pushing streams into increasingly degraded states, and the window of opportunity for restoration will not stay open forever. Therefore, now is the perfect time to apply the science of beaver‐based low‐tech process‐based stream restoration to support building climate resilience across the landscape. Not every stream will be a good candidate for beaver‐based restoration, but we have the tools to know which ones are. Let us use them. This article is categorized under:Science of Water > Hydrological ProcessesWater and Life > Nature of Freshwater EcosystemsWater and Life > Conservation, Management, and Awareness [ABSTRACT FROM AUTHOR]

Many areas are experiencing increasing stream temperatures due to climate change, and some are experiencing reduced summer stream flows and water availability. Because dam building and pond formation by beaver can increase water storage, stream cooling, and riparian ecosystem resilience, beaver have been proposed as a potential climate adaption tool. Despite the large number of studies that have evaluated how beaver activity may affect hydrology and water temperature, few experimental studies have quantified these outcomes following beaver relocation. We evaluated changes in temperature and water storage following the relocation of 69 beaver into 13 headwater stream reaches of the Skykomish River watershed within the Snohomish River basin, Washington, USA. We evaluated how beaver dams affected surface and groundwater storage and stream temperature. Successful relocations created 243 m3 of surface water storage per 100 m of stream in the first year following relocation. Dams raised water table elevations by up to 0.33 m and stored approximately 2.4 times as much groundwater as surface water per relocation reach. Stream reaches downstream of dams exhibited an average decrease of 2.3°C during summer base‐flow conditions. We also assessed how dam age, condition, maintenance frequency, and pond morphology influenced stream temperature at naturally colonized wetland complexes. Our findings demonstrate that dam building can increase water storage and reduce stream temperatures in the first year following successful beaver relocation. Fluvial and floodplain morphology of candidate reaches for relocation is an important consideration because it determines the type and magnitude of response. Relocation to reaches with existing small, abandoned ponds may address thermal criteria by conversion from warming to cooling reaches, whereas relocation within large, abandoned complexes or vacant habitat may result in greater water storage. Although beaver relocation can be an effective climate adaptation strategy to retain more stable hydrologic regimes and water quality in our study area, there appear to be regionally specific environmental and geomorphic factors that influence how beaver affect water storage and temperature. More research is needed to investigate how and why these regional differences affect water storage and stream temperature response in beaver‐influenced systems. [ABSTRACT FROM AUTHOR]

Recent museum, archaeological, and observer record evidence suggests that North American beaver (Castor canadensis) were historically native to the watersheds of California’s coast, including San Francisco Bay. A wide variety of animals are abundantly represented in Native American petroglyphs and pictographs with their representations fulfilling intentions ranging from the mundane to ceremonial and mythological purposes. However, beaver symbols are poorly represented in California rock art and absent from the San Francisco Bay Area. A novel record, in the form of Western Message Petroglyphs, suggests that a beaver lodge was present in the late nineteenth century in the Alameda Creek watershed, potentially the last evidence of beaver prior to their extirpation in the region by the fur trade.

Abstract Many areas are experiencing increasing stream temperatures due to climate change, and some are experiencing reduced summer stream flows and water availability. Because dam building and pond formation by beaver can increase water storage, stream cooling, and riparian ecosystem resilience, beaver have been proposed as a potential climate adaption tool. Despite the large number of studies that have evaluated how beaver activity may affect hydrology and water temperature, few experimental studies have quantified these outcomes following beaver relocation. We evaluated changes in temperature and water storage following the relocation of 69 beaver into 13 headwater stream reaches of the Skykomish River watershed within the Snohomish River basin, Washington, USA. We evaluated how beaver dams affected surface and groundwater storage and stream temperature. Successful relocations created 243 m3 of surface water storage per 100 m of stream in the first year following relocation. Dams raised water table elevations by up to 0.33 m and stored approximately 2.4 times as much groundwater as surface water per relocation reach. Stream reaches downstream of dams exhibited an average decrease of 2.3°C during summer base‐flow conditions. We also assessed how dam age, condition, maintenance frequency, and pond morphology influenced stream temperature at naturally colonized wetland complexes. Our findings demonstrate that dam building can increase water storage and reduce stream temperatures in the first year following successful beaver relocation. Fluvial and floodplain morphology of candidate reaches for relocation is an important consideration because it determines the type and magnitude of response. Relocation to reaches with existing small, abandoned ponds may address thermal criteria by conversion from warming to cooling reaches, whereas relocation within large, abandoned complexes or vacant habitat may result in greater water storage. Although beaver relocation can be an effective climate adaptation strategy to retain more stable hydrologic regimes and water quality in our study area, there appear to be regionally specific environmental and geomorphic factors that influence how beaver affect water storage and temperature. More research is needed to investigate how and why these regional differences affect water storage and stream temperature response in beaver‐influenced systems.

Abstract Eurasian beaver (Castor fiber) were nearly hunted to extinction but have recovered to occupy much of their former range. Beaver were extirpated from Great Britain c. 400 years ago but have recently been reintroduced. The River Otter catchment, Devon was the site of the first licensed wild release of beavers in England. With further releases being considered, there is a need to better understand population dynamics of this native, keystone species to inform conservation and management. Field signs were surveyed from 2015 to 2021. A semi‐automated territory detection method was adopted to estimate territory counts. A spatially explicit model was developed to estimate the ecological territory capacity of the catchment. Future territory expansion was modelled using logistic growth curves; initial growth rate was estimated from observed territory counts and the estimated territory capacity range was used to define the limiting value of the growth curve. Beaver territory removal was simulated, across a range of management intensities and start times, to determine potential impacts of translocation or lethal control upon population dynamics. Territory numbers increased from four to 18, inclusive of four additionally released individuals, during study period. In the absence of population management, the territory capacity of the catchment was estimated to range between 120 and 183; this may be reached between 2028 and 2057. Simulated territory removal, where territories were removed at a fixed rate from the sum of the estimated total population and the population increase for that year, demonstrated large uncertainties in predicted population responses. Simulations with territory removals >3/year all predicted potential population collapse. This finding emphasizes the need for caution when considering population management strategies; translocation of animals out of the catchment or culling should be considered only when populations are established and all alternatives have been considered. These results provide critical information for the expected rate and magnitude of beaver population change in the River Otter catchment. The methods provide a reproducible and generalizable approach for understanding beaver population change, which can inform policy on the reintroduction of beavers and the potential timing and intensity of future beaver population management.