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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]

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]

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]

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]

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]

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]

Muskrats are one of North America’s most widely distributed semi-aquatic mammals; however, populations are declining in many areas of North America yet expanding as an invasive species elsewhere. Its importance in native habitats and impacts in non-native environments warrants investigation into their habitat requirements. We compared the influence of several environmental factors to determine drivers of habitat selection. We hypothesized that distance to vegetation, vegetation type, distance to beaver lodges, beaver presence, and pond morphometry would influence muskrat habitat use. Through field surveys and GIS analyses, we used logistic regression and non-parametric approaches to assess various habitat metrics. Relative to randomly created points, muskrat huts were closer to adjacent vegetation, with more huts adjacent to cattail stands than other types of vegetation, although rushes (Juncus sp.) were most heavily browsed by muskrats. Although there were more huts and push-ups on occupied beaver ponds than on abandoned ponds, overall presence of muskrats did not differ. Push-ups exhibited random placement in ponds and weak associations with other variables, despite being adjacent to smaller vegetation stands with higher browse intensity than huts. Understanding habitat use allows unique insights into a species declining in native habitats yet creating ongoing challenges as an invasive species. [ABSTRACT FROM AUTHOR]

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]

Beavers are large, semiaquatic rodents in the genus Castor native to the temperate Northern Hemisphere. The European beaver (Castor fiber) has an undoubtedly positive impact on the environment: it is a key species, which means that it plays a critical role in the biodiversity of ecosystems and that many species, some endangered or threatened, rely on beavers and the landscapes they build. In this way, there are many benefits that humans and other animal species can get from beavers. Also, dam construction has the potential to alter the hydrology, geomorphology, biogeochemistry, and ecosystems of river corridors and the feedbacks between them, thus the beaver is also recognized as an 'ecosystem engineer'. However, beavers can also generate conflict situations because not all watercourses can withstand the intense construction of dams. Thus, in many contexts, the engineering activities of the beaver may come into direct conflict with other priorities: agriculture, urban land use, forestry, irrigation. Beavers occasionally damage selected trees, but the worst damage is caused by their burrows, which raise water levels in streams, ponds or lakes, flooding the ground and frequently killing large areas of valuable trees in the forest. There are proven costs to agriculture that result from the impact of beavers, and these will have to be fully taken into account in future decisions to manage the beaver population. The ecological impact of the Eurasian beaver on habitat structure has been little investigated in Europe and includes in particular the changes that take place during dam construction activities. The purpose of this study was to summarize the publications that analyse the ecological impact of beaver (Castor fiber). [ABSTRACT FROM AUTHOR]

The "giant" beaver, Trogontherium cuvieri Fischer, 1809, is an extinct species that was widely distributed from the Late Pliocene to the Late Pleistocene all over the Palaearctic Realm. The global environment during this period is characterized by periodic and extreme climate changes, and most mammalian groups experienced rapid evolution during this period. However, the morphology of T. cuvieri shows long-term stability or conservatism, so theoretically it must have adopted certain ecological strategies to cope with drastic changes of climate. New T. cuvieri materials from Jinyuan Cave cover 5 different horizons from Early Pleistocene to Middle Pleistocene (from ~2.1 Ma to ~0.5 Ma by magnetic dating). Its five occurrences are not coupled with climate change in Northeast China. To explore how its persistence in this area in the Pleistocene could help us understand the ecological adaptation mechanism of the species, we used tooth micro-wear analysis to establish a micro-wear feature matrix for T. cuvieri from different horizons, and performed a statistical analysis based on this matrix. The results of ranking analysis show that there are significant differences in the diet of T. cuvieri in different chronological periods, which demonstrates that a plastic ecological niche is an important mechanism for the species' ecological adaptation, and is possibly the principal factor in persistence of T. cuvieri in Northeast China. [ABSTRACT FROM AUTHOR]

Muskrats Ondatra zibethicus are semiaquatic herbivores experiencing long-term and widespread population declines across North America. Translocation may be a viable tool to bolster or reestablish local populations; however, subsequent effects of translocation on muskrats are unknown. We live-trapped and translocated radiomarked muskrats (n = 65) during the summers of 2018-2019 in Voyageurs National Park, MN, USA and assessed post-translocation effects on weekly survival probabilities and space-use patterns. We did not observe homing behavior, though individuals moved an average of 2.2 km (SE = 0.30 km) from release sites and established home ranges within ~8 days (SE = 1.16 days) post-translocation. Weekly post-translocation survival probabilities (0.95, SE = 0.001) and average home-range sizes (2.52 ha, SE = 0.44 ha) were similar to other studies of non-translocated muskrats. Our most-supported known-fate survival model revealed muskrats using beaver Castor canadensis lodges had greater weekly survival probabilities. Additionally, weekly muskrat survival varied between years suggesting a positive response to a novel soft-release technique applied in 2019. Our study provides the first empirical assessment of translocation effects on muskrats and suggests translocation may be effective for establishing or enhancing local muskrat populations. Additionally, our study suggests beaver lodges may confer fitness benefits to sympatric muskrats particularly during dispersal. [ABSTRACT FROM AUTHOR]

A century ago, overhunting had reduced Eurasian beaver Castor fiber populations to c. 1200 animals in scattered refugia from France to Mongolia. Reintroductions and natural spread have since restored the species to large areas of its original range. Population has more than tripled since the first modern estimate in 1998; the minimum estimate is now c. 1.5 million.Range expansion 2000–2020 has been rapid, with large extensions in western and south‐central Europe, southern Russia, and west and central Siberia. Beavers are now re‐established in all countries of their former European range except for Portugal, Italy, and the southern Balkans; they occur broadly across Siberia to Mongolia, with scattered populations father east. About half of the world population lives in Russia. Populations appear to be mature in much of European Russia, Belarus, the Baltic States, and Poland.There is a significant population of North American beaver Castor canadensis in Finland and north‐west Russia. Most other 20th‐Century introductions of this species have become extinct or been removed.Recent DNA studies have improved understanding of Castor fiber population prehistory and history. Two clades, east and west, are extant; a third 'Danube' clade is extinct. Refugial populations were strongly bottlenecked, with loss of genetic diversity through genetic drift.Future range extension, and large increases in populations and in impacts on freshwater systems, can be expected. Beavers are now recolonising densely populated, intensely modified, low‐relief regions, such as England, the Netherlands, Belgium, and north‐west Germany. They will become much more common and widespread there in coming decades. As beavers are ecosystem engineers with profound effects on riparian habitats, attention to integrating beaver management into these landscapes using experience gained in other areas – before the rapid increase in population densities and impacts occurs – is recommended. [ABSTRACT FROM AUTHOR]

Muskrats Ondatra zibethicus are semiaquatic herbivores experiencing long-term and widespread population declines across North America. Translocation may be a viable tool to bolster or reestablish local populations; however, subsequent effects of translocation on muskrats are unknown. We live-trapped and translocated radiomarked muskrats (n = 65) during the summers of 2018–2019 in Voyageurs National Park, MN, USA and assessed post-translocation effects on weekly survival probabilities and space-use patterns. We did not observe homing behavior, though individuals moved an average of 2.2 km (SE = 0.30 km) from release sites and established home ranges within ∼8 days (SE = 1.16 days) post-translocation. Weekly post-translocation survival probabilities (0.95, SE = 0.001) and average home-range sizes (2.52 ha, SE = 0.44 ha) were similar to other studies of non-translocated muskrats. Our most-supported known-fate survival model revealed muskrats using beaver Castor canadensis lodges had greater weekly survival probabilities. Additionally, weekly muskrat survival varied between years suggesting a positive response to a novel soft-release technique applied in 2019. Our study provides the first empirical assessment of translocation effects on muskrats and suggests translocation may be effective for establishing or enhancing local muskrat populations. Additionally, our study suggests beaver lodges may confer fitness benefits to sympatric muskrats particularly during dispersal. [ABSTRACT FROM AUTHOR]

European beaver (Castor fiber L. 1758) is the biggest rodent living in Europe. It is a semi-aquatic animal known for building dams and burrows. European beaver is a potential host for a wide range of parasites and other infectious diseases. In Slovakia, there is an increasing number of beavers but the data about their parasitic fauna are missing. Our work is the first documentation about the beaver's parasitofauna in Slovakia. In a 1-year study, we collected and examined 19 beaver fecal samples from the vicinity of beaver burrows inhabiting three particular localities at the Danube, Topľa, and Laborec rivers in Slovakia. In these fecal samples, 4 different species of intestinal endoparasites were detected as follows: oocysts of Cryptosporidium, cysts of Giardia, eggs of Stichorchis subtriquetrus, and eggs and larvae of Travassosius rufus. Parasites were confirmed only in samples collected at river Topľa. Based on our results, we can conclude that European beaver can be an important source of parasitic contamination of surface waters especially in the localities shared by people. [ABSTRACT FROM AUTHOR]

Beavers have the ability to modify ecosystems profoundly to meet their ecological needs, with significant associated hydrological, geomorphological, ecological, and societal impacts. To bring together understanding of the role that beavers may play in the management of water resources, freshwater, and terrestrial ecosystems, this article reviews the state‐of‐the‐art scientific understanding of the beaver as the quintessential ecosystem engineer. This review has a European focus but examines key research considering both Castor fiber—the Eurasian beaver and Castor canadensis—its North American counterpart. In recent decades species reintroductions across Europe, concurrent with natural expansion of refugia populations has led to the return of C. fiber to much of its European range with recent reviews estimating that the C. fiber population in Europe numbers over 1.5 million individuals. As such, there is an increasing need for understanding of the impacts of beaver in intensively populated and managed, contemporary European landscapes. This review summarizes how beaver impact: (a) ecosystem structure and geomorphology, (b) hydrology and water resources, (c) water quality, (d) freshwater ecology, and (e) humans and society. It concludes by examining future considerations that may need to be resolved as beavers further expand in the northern hemisphere with an emphasis upon the ecosystem services that they can provide and the associated management that will be necessary to maximize the benefits and minimize conflicts. This article is categorized under:Water and Life > Nature of Freshwater Ecosystems [ABSTRACT FROM AUTHOR]

The European beaver Castor fiber is well‐known as an ecosystem engineer that greatly affects landscape structure, biodiversity as well as physical and chemical properties of surface water bodies. Beaver ponds alter surface water bodies by raising water elevation, decreasing flow velocity and altering the morphology of streams or drainage ditches, which can reduce the concentrations of organic carbon (OC) and nutrients (N, P). Recent studies indicated that mercury transforms into hazardous and neurotoxic methylmercury (MeHg) in beaver impoundments by biological processes in anaerobic conditions. However, the knowledge about nutrients and MeHg levels in impounded forest waterbodies is scarce in Lithuania. We aimed to ascertain the alteration in concentrations and stocks of OC, nutrients and MeHg in water and sediments from upstream and downstream, as well as within beaver dams and ponds during the growing seasons of 2016–2018. Results showed higher concentrations of dissolved organic carbon (DOC) and nutrients (P and N) in upstream water samples compared to those of downstream from beaver dams. Meanwhile, in sediments mean stocks of OC, P and N were the highest in the middle part of the ponds and in beaver dams. Moreover, the concentrations and stocks of MeHg in sediments were higher in beaver dams than in any other parts of beaver impoundments (upstream, mid‐pond, pond periphery and downstream). We conclude that dam bottom sediments were rich in OC, N and P, and at the same time, contained toxic MeHg. Therefore, beaver dams could act as a trickle filter by improving water quality, in our case, DOC, N and P leaching, from riparian forests and soils, but may also act as hotspots of mercury methylation. [ABSTRACT FROM AUTHOR]

The European beaver Castor fiber is well-known as an ecosystem engineer that greatly affects landscape structure, biodiversity as well as physical and chemical properties of surface water bodies. Beaver ponds alter surface water bodies by raising water elevation, decreasing flow velocity and altering the morphology of streams or drainage ditches, which can reduce the concentrations of organic carbon (OC) and nutrients (N, P). Recent studies indicated that mercury transforms into hazardous and neurotoxic methylmercury (MeHg) in beaver impoundments by biological processes in anaerobic conditions. However, the knowledge about nutrients and MeHg levels in impounded forest waterbodies is scarce in Lithuania. We aimed to ascertain the alteration in concentrations and stocks of OC, nutrients and MeHg in water and sediments from upstream and downstream, as well as within beaver dams and ponds during the growing seasons of 2016-2018. Results showed higher concentrations of dissolved organic carbon (DOC) and nutrients (P and N) in upstream water samples compared to those of downstream from beaver dams. Meanwhile, in sediments mean stocks of OC, P and N were the highest in the middle part of the ponds and in beaver dams. Moreover, the concentrations and stocks of MeHg in sediments were higher in beaver dams than in any other parts of beaver impoundments (upstream, mid-pond, pond periphery and downstream). We conclude that dam bottom sediments were rich in OC, N and P, and at the same time, contained toxic MeHg. Therefore, beaver dams could act as a trickle filter by improving water quality, in our case, DOC, N and P leaching, from riparian forests and soils, but may also act as hotspots of mercury methylation. [ABSTRACT FROM AUTHOR]

Social interactions among individuals play a central role in behavioural ecology and studying cohesion of monogamous pairs is important to understand their social relationships. Here, we tested five hypotheses to investigate patterns of pair cohesion in an obligate monogamous mammal, the Eurasian beaver, Castor fiber. We hypothesized that pair cohesion is related to the spatial structure of the territory, territory defence, resource competition, offspring provisioning and the age difference between pair members. We analysed GPS data of 14 beaver pairs and calculated the distance between pair members, and the proportion of territory and core area overlap. While overall territory size was similar between partners and overlap was high, the distance between pair members was large, averaging 500 m, and increased with increasing territory size. Moreover, the proportion of core area overlap was comparatively low and decreased with territory size, also indicating low pair cohesion. Pair members were closest at the beginning and end of their nightly activity periods, suggesting that variation in pair cohesion was caused by the spatial structure of territories with the lodge serving as a central place. We found no support for the other hypotheses, but the overall low pair cohesion might nevertheless serve to increase territory defensibility and reduce intrapair competition for resources. Ultimately, low pair cohesion might be caused by the obligate monogamous mating system of beavers, leading to the defence of spatially structured territories rather than the defence of a partner. • Beavers exhibit low pair cohesion, with pair members being on average 500 m apart. • This may increase territory defence efficiency via enhanced patrolling effort. • Low pair cohesion may also reduce predation risk and competition for food. • Low pair cohesion might be caused by the beavers' monogamous mating system. [ABSTRACT FROM AUTHOR]

Beaver canals and their environmental effects are much less studied than beaver dams, despite being widespread in some beaver-inhabited areas. In this study, we completed a systematic review of previous research on the structure and ecosystem effects of beaver canals to provide an increasingly holistic understanding of these landscape features. Specifically, we: 1) summarized why, where, when, and how beaver develop canals; 2) chronicled all published descriptions on beaver canal morphology; and 3) summarized the literature on the environmental effects of beaver canals. Thirty-one relevant studies were identified and incorporated into this review. Beaver canals have been identified in numerous environments ranging from largely undeveloped mountainous regions to heavily developed agricultural landscapes. Beaver primarily develop canals to increase accessibility to riparian resources, facilitate transport of harvested resources, and to decrease predation risk. As with beaver dams, beaver canals exhibit large structural variability, particularly in lengths, which can be over 0.5 km. Widths of about 1 m and depths of about 0.5 m are common. Beaver canals alter watershed hydrology by creating new aquatic habitats, connecting isolated aquatic features, and diverting water into colonized areas. Beaver canals have been identified as favored habitats for several biotic species and are sometimes used during critical life stages (e.g. dispersal). In addition to increasing overall floral and faunal species richness and diversity, beaver canals may benefit biota by mitigating habitat fragmentation and climate change impacts. Based on the results of this review, incorporating beaver canals into stream restoration practices may be environmentally beneficial. [ABSTRACT FROM AUTHOR]

There is practically no stream or river without non-native beaver impact, past or current, in Tierra del Fuego (TDF), Argentina. In this study, we evaluated the effect of beaver activity on water quality and algal composition in forested streams and rivers from TDF. We sampled five streams and rivers with current beaver activity during the austral summers of 2016 and 2017. Also, three streams which have had beaver activity in the past but with no activity since several years ago (ca. 10 years) were included in the study. Sampling was performed in a paired design upstream and downstream the beaver dam or the site where it used to be located. Physical and chemical variables as well as phytoplankton and epilithon chlorophyll-a and algal composition were monitored. Results show a decrease in dissolved organic carbon concentration and an increase in both phytoplankton abundance and periphyton taxa richness downstream the dam. The diatom Hannaea arcus was present in both communities only in impacted sites, thus influencing the clustering. In this study, we show that beaver activity influences periphyton richness and composition, and phytoplankton abundance in impacted streams and rivers, though it exerted a minor influence on water physical and chemical variables. [ABSTRACT FROM AUTHOR]

Background: Long noncoding RNAs (lncRNAs) have roles in gene regulation, epigenetics, and molecular scaffolding and it is hypothesized that they underlie some mammalian evolutionary adaptations. However, for many mammalian species, the absence of a genome assembly precludes the comprehensive identification of lncRNAs. The genome of the American beaver (Castor canadensis) has recently been sequenced, setting the stage for the systematic identification of beaver lncRNAs and the characterization of their expression in various tissues. The objective of this study was to discover and profile polyadenylated lncRNAs in the beaver using high-throughput short-read sequencing of RNA from sixteen beaver tissues and to annotate the resulting lncRNAs based on their potential for orthology with known lncRNAs in other species. Results: Using de novo transcriptome assembly, we found 9528 potential lncRNA contigs and 187 high-confidence lncRNA contigs. Of the high-confidence lncRNA contigs, 147 have no known orthologs (and thus are putative novel lncRNAs) and 40 have mammalian orthologs. The novel lncRNAs mapped to the Oregon State University (OSU) reference beaver genome with greater than 90% sequence identity. While the novel lncRNAs were on average shorter than their annotated counterparts, they were similar to the annotated lncRNAs in terms of the relationships between contig length and minimum free energy (MFE) and between coverage and contig length. We identified beaver orthologs of known lncRNAs such as XIST, MEG3, TINCR, and NIPBL-DT. We profiled the expression of the 187 high-confidence lncRNAs across 16 beaver tissues (whole blood, brain, lung, liver, heart, stomach, intestine, skeletal muscle, kidney, spleen, ovary, placenta, castor gland, tail, toe-webbing, and tongue) and identified both tissue-specific and ubiquitous lncRNAs. Conclusions: To our knowledge this is the first report of systematic identification of lncRNAs and their expression atlas in beaver. LncRNAs—both novel and those with known orthologs—are expressed in each of the beaver tissues that we analyzed. For some beaver lncRNAs with known orthologs, the tissue-specific expression patterns were phylogenetically conserved. The lncRNA sequence data files and raw sequence files are available via the web supplement and the NCBI Sequence Read Archive, respectively. [ABSTRACT FROM AUTHOR]

Territoriality is an important process shaping population dynamics, and the defence of a territory is crucial for individuals to increase the duration of territory occupancy and, consequently, reproductive success. However, little is known about how the frequency of territory intrusions and subsequent territorial behaviours and aggression by territory owners are affected by external factors, such as population density. This is important because it can affect mate change (the replacement of one pair member) and dispersal, a key ecological process.The aim of this study was to investigate the behavioural and spatial response of territory owners to intruder pressure as a function of population density in a territorial, monogamous mammal, the Eurasian beaver (Castor fiber).Using a combination of GPS technology, scent experiments, camera trap data and tail scar observations from an individual‐based long‐term study, we investigated the factors influencing spatial movement patterns by territory owners in response to a simulated intruder and the factors affecting territory intrusions.We found consistent inverse density‐dependent patterns in territorial behaviours and evidence of conspecific aggression. At lower densities, territory owners detected more simulated intrusions, showed more territorial reactions and experienced increased conspecific aggression as indicated by tail scars, suggesting increased intruder pressure.Inverse density‐dependent territorial behaviour and aggression suggest a potential mechanistic link between inverse density‐dependent natal dispersal and mate change. At low population densities, increased dispersal amplifies intruder pressure, leading to the observed increases in territorial behaviours, conspecific aggression and previously observed mate turnover, which in turn might increase natal dispersal. Our study demonstrates how population density can affect the behaviour and space use of individuals, which is important for territory occupancy and fitness. [ABSTRACT FROM AUTHOR]

Beavers have been analyzed in several studies examining trace elements (TEs) in wildlife; however, most of these studies were undertaken in areas with known environmental pollutants. To understand and quantify natural enrichments of TEs in beaver tissue, samples of kidney, liver, muscle from 28 animals were compared with bark from 40 species of trees and shrubs, from the same, uncontaminated watershed. Pearson correlation and factor analysis show that conservative, lithophile elements such as Al, Ga, Th, and Y, all surrogates for mineral dust particles, explain 61% of the variation in the bark data. In contrast, Cd, Co, Cu, Mn, Mo, Ni, Rb, Se, Sr, and Tl in bark are independent of Al, and therefore most likely occur in non-mineral forms. Comparing tissue concentrations of beaver and bark, the organs are enriched in micronutrients such as Cu, Fe, Mo, Se, and Zn, but also non-essential, benign elements such as Cs and Rb, and potentially toxic elements such as Cd and Tl. Thus, the elements most enriched in beaver organs are those that apparently occur in biological form in the plant tissue. The elements enriched in these animals, relative to bark, appear to offer the most promise for monitoring environmental contamination by TEs using beavers. The majority of TEs of environmental relevance are most abundant in beaver kidney. However, monitoring studies must consider the variation in TE concentrations in beaver tissue, including those due to sex and age. Also, due consideration must be given to background concentrations of TEs in the vegetation composing the diet of the animals. The natural enrichment in the case of elements such as Cd, in beaver tissue relative to bark, is profound. These data establish critical baseline values for TEs in beavers in an unpolluted environment, thereby allowing for their use as model organisms in tracking how heavy metal pollutants may affect wildlife. [Display omitted] • Al, Ga, Th, Y and lanthanides in bark reflect dust and explain 61% of variance. • Cd, Co, Cu, Mn, Mo, Ni, Rb, Se, Sr, and Tl in bark are independent of Al. • Beaver tissues are naturally enriched in micronutrients Cu, Fe, Mo, Se and Zn. • Beavers are enriched in Cs and Rb (benign), and Cd and Tl (potentially toxic). • Elements enriched in beaver tissue are apparently in biological form in plant tissue. [ABSTRACT FROM AUTHOR]

• Eurasian male beavers possess one double uterus (uterus duplex) • The length of the horns is the most differential feature of uterus masculinus. • In uterus masculinus membrane receptors: ZIP9 and GPER are present. • GPER expression in uterus masculinus is lower than those in the female uterus. • Levels of progesterone and estradiol but not testosterone are lower than in the female uterus. The phenomenon of remaining paramesonephric ducts (uterus masculinus) in males of some animal species concerning its role is still an unresolved issue. Now it is well-recognized that sex hormonal regulation of reproductive physiology involves also fast nongenomic control of cellular processes through noncanonical signaling. Herein, in the uterus masculinus of Eurasian beaver membrane androgen receptor (metal ion transporter Zrt- and Irt-like protein 9; ZIP9) and membrane estrogen receptor (G protein-coupled estrogen receptor; GPER) were studied. Scanning electron microscopy together with anatomical analysis revealed that Eurasian male beavers possess one double uterus (uterus duplex). Two odd parts open into the vagina but do not form a common lumen. The length of the horns is the most differential feature of this organ in studied animals. Uterus masculinus is not a tightly closed tubular structure. Histological analysis showed an analogy to the female uterus structure however no glands but gland-like structures were observed. The presence and abundant localization of ZIP9 and GPER proteins in cells of uterus masculinus was confirmed by immunohistochemistry while their expression was measured by western blotting. GPER expression in remnants was lower (P < 0.001) than those in the female uterus. Parallelly, the concentration of progesterone and estradiol but not testosterone was lower (P < 0.05 and P < 0.01, respectively) in comparison to the female uterus. Our study, for the first time, reports the involvement of fast hormonal regulation in the uterus masculinus of Eurasian beavers reflecting the participation of this organ in the creation local hormonal environment. Moreover, the uterus masculinus seems to be a useful research model for understanding and resolving urgent biological problems such as gender identities and having children by women with a lack of uterus or anatomical barriers on this level. [ABSTRACT FROM AUTHOR]

The European beaver Castor fiber is well-known as an ecosystem engineer that greatly affects landscape structure, biodiversity as well as physical and chemical properties of surface water bodies. Beaver ponds alter surface water bodies by raising water elevation, decreasing flow velocity and altering the morphology of streams or drainage ditches, which can reduce the concentrations of organic carbon (OC) and nutrients (N, P). Recent studies indicated that mercury transforms into hazardous and neurotoxic methylmercury (MeHg) in beaver impoundments by biological processes in anaerobic conditions. However, the knowledge about nutrients and MeHg levels in impounded forest waterbodies is scarce in Lithuania. We aimed to ascertain the alteration in concentrations and stocks of OC, nutrients and MeHg in water and sediments from upstream and downstream, as well as within beaver dams and ponds during the growing seasons of 2016--2018. Results showed higher concentrations of dissolved organic carbon (DOC) and nutrients (P and N) in upstream water samples compared to those of downstream from beaver dams. Meanwhile, in sediments mean stocks of OC, P and N were the highest in the middle part of the ponds and in beaver dams. Moreover, the concentrations and stocks of MeHg in sediments were higher in beaver dams than in any other parts of beaver impoundments (upstream, mid-pond, pond periphery and downstream). We conclude that dam bottom sediments were rich in OC, N and P, and at the same time, contained toxic MeHg. Therefore, beaver dams could act as a trickle filter by improving water quality, in our case, DOC, N and P leaching, from riparian forests and soils, but may also act as hotspots of mercury methylation. [ABSTRACT FROM AUTHOR]

Aim: To determine whether reintroduced beavers, as an example of native herbivorous megafauna, can increase freshwater biodiversity at the landscape scale and to compare effects on two contrasting taxonomic groups. Location: South‐central Sweden. Methods: We collected data on plant and water beetle composition and supporting environmental variables from 20 closely located wetlands, half created from the damming of streams by beavers—beaver ponds (BP), and half by other, mainly natural (e.g. topographic, river migration) means—other wetlands (OW). Differences in species composition and plant growth strategy (i.e. competitor, stress tolerator or ruderal) between wetland types were assessed using multivariate analyses. Results: The species pool of both taxonomic groups was higher in BP than OW (plants + 17%; beetles + 15%). For both groups, the number of species unique to BP was 50% higher than those unique to OW. Plant and beetle compositions differed significantly between wetlands, most strongly for plants, while rarity scores showed no difference, and the incidence of invasive species was negligible. Plant composition was mostly influenced by open water, bare ground and woody debris in BP, and plant cover, height and leaf litter in OW. This was consistent with the characterization of BP vegetation by ruderal plants and OW by competitors and stress tolerators. A significant residual effect of wetland type on plant, but not beetle composition, suggests that beavers exert important direct effects on some biota (e.g. via herbivory) independent of the indirect effects they exert via environmental change. Main conclusions: Beaver‐created ponds support novel biodiversity that is not merely a subset of that found elsewhere in the same landscape. As such, re‐establishing beaver populations where they are native should benefit freshwater biodiversity, but effects may be context and taxon specific. Beavers alone cannot solve the freshwater biodiversity crisis, but recognizing the widespread importance of herbivorous megafauna in maintaining heterogeneity and creating novel habitat will be a positive step. [ABSTRACT FROM AUTHOR]

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. Unlabelled Image • Beavers enhance multi-season alluvial floodplain hydrologic connectivity. • Enhanced floodplain water storage creates reducing conditions and mobilizing metals. • Beaver pond return flows source natural metals to the main channel. • Beaver-induced floodplain exchange alters river chemistry in small and large streams. • Mobility of metals and contaminants likely impacts beaver-enabled stream restoration. [ABSTRACT FROM AUTHOR]

Our pioneering data provide the first comprehensive view of placental transcriptome of the beaver during single and multiple gestation. RNA-Seq and a de novo approach allowed global pattern identification of C. fiber placental transcriptome. Non-redundant beaver transcriptome comprised 211,802,336 nt of placental transcripts, grouped into 128,459 contigs and clustered into 83,951 unigenes. An Ensembl database search revealed 14,487, 14,994, 15,004, 15,267 and 15,892 non-redundant homologs for Ictidomys tridecemlineatus, Rattus norvegicus, Mus musculus, Homo sapiens and Castor canadensis, respectively. Due to expression levels, the identified transcripts were divided into two sets: non-redundant and highly expressed (FPKM > 2 in at least three examined samples), analysed simultaneously. Among 17,009 highly expressed transcripts, 12,147 had BLASTx hits. GO annotations (175,882) were found for 4301 transcripts that were assigned to biological process (16,386), cellular component (9149) and molecular function (8338) categories; 666 unigenes were also classified into 122 KEGG pathways. Comprehensive analyses were performed for 411 and 3078 highly expressed transcripts annotated with a list of processes linked to 'placenta' (31 GO terms) or 'embryo' (324 GO terms), respectively. Among transcripts with entire CDS annotation, 281 (placenta) and 34 (embryo) alternative splicing events were identified. A total of 8499 putative SNVs (~ 6.2 SNV/transcript and 1.7 SNV/1 kb) were predicted with 0.1 minimum frequency and maximum variant quality (p value 10e−9). Our results provide a broad-based characterization of the global expression pattern of the beaver placental transcriptome. Enhancement of transcriptomic resources for C. fiber should improve understanding of crucial pathways relevant to proper placenta development and successful reproduction. [ABSTRACT FROM AUTHOR]

The studies of the craniometric features in European beaver (Castor fiber L.,1758) were performed using the material of 25 skulls, including 12 females and 13 males from the Pomorze and Kujawy region. For each skull 30 measurements were taken to provide the grounds for the variation in craniometric features and the significance of differences between sexes. In two cases there were observed significant and in three - highly significant differences between males and females of that species. Interestingly, in the shaft of the occipital bone there was found a profound and vast fossa of the skull base. [ABSTRACT FROM AUTHOR]

The European beaver (Castor fiber L.) is the largest free-living rodent in Eurasia. The present work aimed to determine sex- and season-related changes in leptin receptor (Ob-R) expression in the hypothalamic–pituitary–gonadal/adrenal axes and uterus of beavers during breeding- (April), post-breeding- (July), and pre-breeding- (November) periods. The expression of Ob-R gene and protein was found in all analyzed tissues. The expression of Ob-R mRNA remained constant in the hypothalamus of both sexes during the analyzed stages. Sex- and season-related changes were found in the pituitary gland; the greatest level was observed in July in both sexes. The same expression pattern was noted in the testis, whereas in the ovary a lack of seasonal changes was found. In uterine tissues, the greatest expression occurred in November. The impact of season was also demonstrated in the adrenal cortex. In females, a higher Ob-R transcript level was noted in April, while in males, an increased mRNA abundance was noted in November than July. Our study suggests that in the beaver, leptin acting via the Ob-R can be an important endocrine factor engaged in the regulation of reproductive functions and stress response. [ABSTRACT FROM AUTHOR]

Historic beaver-sign (Castor canadensis) survey flights were often conducted over waterways to maximize beaver detections. However, densities determined from strip transect surveys are more useful to compare across and within study areas than waterway indices based on observations per distance flown because transects are more representative of the wider landscape. Yet, it is unknown if, and to what extent, aerial waterway surveys are reflective of transect densities. I conducted aerial surveys for active beaver signs each fall during 2015-2018 over 2 waterway routes and 2 corresponding strip-transect routes. The simple linear regression of transect densities on waterway densities (n=8) yielded a reasonable (R2=0.79) preliminary equation for converting historic waterway data to transect densities. Additionally, visual inspection indicated that converted waterway densities reasonably reflected the trend in transect densities in an area where the wider habitat was similar in terms of beaver harvest, land use, and proportion of water features. Although trend was well-reflected, individual waterway densities in this area were only 57-75% of transect densities. In other areas, where water features were limited, visual inspection suggested the trend of waterway densities was less reflective of transect density trend and individual waterway densities overestimated transect densities (up to 309%). Nevertheless, while transect densities are better for comparisons within and across study areas, waterway surveys are still important for timely and specific within-study area insights. This research provides useful benchmark examples of reliability regarding waterway observation indices converted to densities for conservation, research, and management of beavers and their ecosystems. Because these conclusions are based on a small sample, additional research is recommended to better define this relationship especially in areas with differing habitats, beaver harvests, and land use patterns. [ABSTRACT FROM AUTHOR]

The aim of the present work was to examine and compare the fatty acid composition of muscle tissues from eleven pregnant beaver (Castor fiber) females and their foetuses. The females were culled during warrantable early spring beaver hunting period (from the beginning of March until the middle of April). The fat content of the muscles of beaver female was 2.0 times higher (P < 0.001) than that of the muscles of their foetuses before birth. A total number of 33 and 34 fatty acids of various chain lengths and saturation levels, including 5 trans isomers, were identified, respectively, in the intramuscular fat (IMF) of muscle tissues from beaver females and their foetuses. Considerable differences in the proportions of individual fatty acids showed that foetuses during beaver gestation accumulate 1.4 times more total saturated (SFA) and 2.6 times more monounsaturated (MUFA) but 2.7 times less polyunsaturated (PUFA) fatty acids than pregnant females (P < 0.001). Although PUFA/SFA ratio in the tissues of foetuses was by 3.8 times lower (P < 0.001) than in the muscle tissue of females, the differences in n-6/n-3PUFA ratio were not significant (P = 0.133). [ABSTRACT FROM AUTHOR]

Ecosystem engineers can increase biodiversity by creating novel habitat supporting species that would otherwise be absent. Their more routine activities further influence the biota occupying engineered habitats. Beavers are wellknown for transforming ecosystems through dam building and are therefore increasingly being used for habitat restoration, adaptation to climate extremes and in long-term rewilding. Abandoned beaver ponds (BP) develop into meadows or forested wetlands that differ fundamentally from other terrestrial habitats and thus increase landscape diversity. Active BP, by contrast, are superficially similar to other non-engineered shallow wetlands, but ongoing use and maintenance might affect how BP contribute to aquatic biodiversity. We explored the 'within-habitat' effect of an ecosystem engineer by comparing active BP in southern Sweden with coexisting other wetlands (OW), using sedentary (plants) and mobile (water beetles) organisms as indicators. BP differed predictably from OW in environmental characteristics and were more heterogeneous. BP supported more plant species at plot (þ15%) and site (þ33%) scales, and plant beta diversity, based on turnover between plots, was 17% higher than in OW, contributing to a significantly larger species pool in BP (þ17%). Beetles were not differentiated between BP and OW based on diversity measures but were 26% more abundant in BP. Independent of habitat creation beaver are thus significant agents of within-habitat heterogeneity that differentiates BP from other standing water habitat; as an integral component of the rewilding of wetlands re-establishing beaver should benefit aquatic biodiversity across multiple scales. This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'. [ABSTRACT FROM AUTHOR]

Abstract: Increasing air temperatures are changing the arctic tundra biome. Permafrost is thawing, snow duration is decreasing, shrub vegetation is proliferating, and boreal wildlife is encroaching. Here we present evidence of the recent range expansion of North American beaver (Castor canadensis) into the Arctic, and consider how this ecosystem engineer might reshape the landscape, biodiversity, and ecosystem processes. We developed a remote sensing approach that maps formation and disappearance of ponds associated with beaver activity. Since 1999, 56 new beaver pond complexes were identified, indicating that beavers are colonizing a predominantly tundra region (18,293 km2) of northwest Alaska. It is unclear how improved tundra stream habitat, population rebound following overtrapping for furs, or other factors are contributing to beaver range expansion. We discuss rates and likely routes of tundra beaver colonization, as well as effects on permafrost, stream ice regimes, and freshwater and riparian habitat. Beaver ponds and associated hydrologic changes are thawing permafrost. Pond formation increases winter water temperatures in the pond and downstream, likely creating new and more varied aquatic habitat, but specific biological implications are unknown. Beavers create dynamic wetlands and are agents of disturbance that may enhance ecosystem responses to warming in the Arctic. [ABSTRACT FROM AUTHOR]

The foraging patterns and behaviors of predators can be discerned using GPS data. We used GPS data to investigate the temporal patterns of wolverine (Gulo gulo luscus) foraging on large prey in northern Alberta. We built a predictive model of wolverine large-prey events (beaver predation or ungulate scavenging) based on the spatial and temporal patterns of wolverine GPS data at foraging sites we visited in the field in winter. We used this model to predict large-prey events throughout our entire wolverine GPS dataset in winter and summer. We then evaluated how variables related to prey availability, seasonality, competition, and territoriality affected wolverine encounter time, residency time, and return time at predicted large-prey events. We found that wolverines encountered large prey more often in the spring when there is increased beaver and ungulate availability. The total time that wolverines spent at large-prey events was greater in winter (3.11 days [95th percentile = 2.62-3.63 days]) than summer (2.08 days [95th percentile = 1.70-2.51 days]), potentially because prey availability is limited in winter or prey is easier to capture in summer. Wolverines partitioned the total time at events into multiple visits, reducing their residency time and increasing their return time with each revisit, indicating biomass decline through time. The time between visits in winter (10.12 days [95th percentile = 7.99-12.56 days]) and summer (8.39 days [95th percentile = 7.18-9.74 days]) suggests wolverines might be patrolling their home range. We also found that wolverine residency time decreased and return time increased when there were other large-prey events available. Moreover, wolverine residency time at events increased when other wolverines were in the area. Our results suggest that large-prey events are important to the energy balance of wolverines and that wolverine foraging behavior is dynamic in response to environmental change. [ABSTRACT FROM AUTHOR]

Aspartic proteinases (AP) form a multigenic group widely distributed in various organisms and includes pepsins (pep), cathepsins D and E, pregnancy associated glycoproteins (PAGs) as well as plant, fungal, and retroviral proteinases. This study describes the transcript identification and expression localization of the AP within the discoid placenta of the Castor fiber. We identified 1257 bp of the AP cDNA sequence, encoding 391 amino acids (aa) of the polypeptide precursor composed of 16 aa signal peptide, 46 aa pro-piece, and 329 aa of the mature protein. Within the AP precursor, one site of potential N-glycosylation (NPS119-121) and two Asp residues (D) specific for the catalytic cleft of AP were identified (VLFDTGSSNLWV91-102 and GIVDTGTSLLTV277-288). The highest homology of the identified placental AP nucleotide and aa sequence was to mouse pepsinogen C (75.8% and 70.1%, respectively). Identified AP also shared high homology with other superfamily members: PAGs, cathepsins, and napsins. The AP identified in this study was named as pepsinogen/PAG-Like (pep/PAG-L). Diversified pep/PAG-L protein profiles with a dominant 58 kDa isoform were identified. Immune reactive signals of the pep/PAG-L were localized within the trophectodermal cells of the beaver placenta. This is the first report describing the placental AP (pep/PAG-L) in the C. fiber. [ABSTRACT FROM AUTHOR]

We installed 12 pond levelers to counter flooding by beavers and developed a cost-benefit analysis for these sites in Alberta, Canada. We also documented beaver management approaches throughout Alberta. Over 3 years, one site required regular maintenance until we designed a modified pond leveler; another required minor modifications. Others required almost no maintenance. Based on a “willingness-to-pay” (WTP) of $0 and discount rate of 3%, installing pond levelers resulted in a present value net benefit of $81,519 over 3 years and $179,440 over 7 years. Scenarios incorporating discount rates of 3% and 7%, horizons of either 3 or 7 years, and varying WTPs resulted in significant net benefits. Provincially, municipalities employed up to seven methods to control beavers: most commonly lethal control and dam removal. Total annual costs provided by 48 municipalities and 4 provincial parks districts were $3,139,223; however, cost-accounting was sometimes incomplete, which makes this a conservative estimate. [ABSTRACT FROM AUTHOR]

A bionic underwater robot swims to generate its propulsion in water, which in turn directly determines its movement stability. Exploring the relationship between the swimming force and the posture is important. This study aims to analyze and model the swimming posture dynamics of a beaver-like robot. The posture dynamics is decomposed into three parts: leg dynamics, body hydrodynamics, and body posture dynamics. First, the leg dynamic model of the beaver-like robot is established using the rigid-fluid integration method. Then, the overall fluid dynamics of the robot is modeled via numerical calculation methods to obtain the forces of the water on the robot body during swimming. Lastly, the swimming posture dynamic model of the robot is constructed to describe the relationship between the leg movement and body posture. The swimming process of the beaver-like robot with bionic alternating and synchronous trajectory is simulated with ADAMS 2019. The proposed modeling method and the swimming posture dynamic model are verified by comparing the simulation and theoretical calculation results of robot posture, which could be used for the swimming posture control of a bionic underwater robot. • A beaver-like robot with bendable webbed feet is designed inspired by beaver. • A swimming posture dynamics model of the robot is established to describe relationship between leg motion and body posture. • The swimming posture dynamic model is verified and could be used for swimming posture control of a bionic underwater robot. • The beaver-like robot has an advantage in swimming velocity among the bionic underwater robots. [ABSTRACT FROM AUTHOR]

Soils in semiarid riparian ecosystems have large carbon (C) stocks that promote water and nutrient availability for productive plant communities consumed by grazing animals. Changes to riparian hydrologic conditions caused by channel incision result in different edaphic conditions and a greater abundance of upland plant species that may be associated with lower soil C stocks. Using riparian meadows alongside Maggie Creek in central Nevada, we show that 27 years of modified grazing practices can repair ecosystem processes and increase the C stocks. We compared C and nitrogen (N) stocks (of soils and plant biomass) on floodplains, terraces, and uplands of reaches where grazing was either modified or excluded to reaches where no changes to grazing practices were made. Grazing management allowed beaver to establish, improving hydrology and lengthening the growing season. These changes allowed C and N to accumulate on geomorphic surfaces that extended from the stream channel to the surrounding hillslopes. A stoichiometric relationship between C and N shows carbon sequestration can reduce nutrient runoff to nearby waterways and may depend on nitrogen availability. Gains in ecosystem carbon ranged from 93 to 452 g C m−2 y−1 and were dominated by increases in soil C. Gains in soil C occurred across the full depth range measured (0–45 cm) and were comparable to those found in restored wetlands and meadows located in more humid ecosystems. Carbon gains exhibited substantial variability caused by microtopography and plant community composition. While grazing exclusion resulted in the largest gains in ecosystem C, managed grazing that limited consumption of riparian plants increased ecosystem C relative to reaches where management wasn't changed. We demonstrate that managed grazing that maintains ecosystem process is compatible with projects aimed at increasing soil carbon in semiarid riparian rangelands. • Gains in carbon were similar to those found in restored grasslands and wetlands. • Significant change in ecosystem carbon occurred in as little as 6–13 years. • Gains in carbon and nitrogen occurred together within soils 0–45 cm. [ABSTRACT FROM AUTHOR]

The pregnancy-associated glycoprotein-like family (PAG-L) is a large group of chorionic products, expressed in the pre-placental trophoblast and later in the post-implantational chorionic epithelium, and are involved in proper placenta development and embryo-maternal interaction in eutherians. This study describes identification of the PAG-L family in the genome of the Eurasian beaver ( Castor fiber L.), named CfPAG-L. We identified 7657 bp of the CfPAG-L gDNA sequence (Acc. No. KX377932), encompassing nine exons (1-9) and eight introns (A-H). The length of the CfPAG-L exons (59-200 bp) was equivalently similar to the only known counterparts of bPAG1, bPAG2, and pPAG2. The length of the CfPAG-L introns ranged 288-1937 bp and was completely different from previously known PAG introns. The exonic CfPAG-L regions revealed 50.3-72.9% homology with equivalent segments of bPAG1 and pPAG2 structure. The intronic CfPAG-L regions alignments revealed a lack of homology. Within the entire CfPAG-L gene, 31 potential single nucleotide variants (SNV: 7 transversions and 24 transitions) were predicted. The identified exonic polymorphic loci did not affect the amino acid sequence of the CfPAG-L polypeptide precursor. This is the first report describing the CfPAG-L gene sequence, structural organization, and SNVs in the Eurasian beaver, one of the largest rodents. [ABSTRACT FROM AUTHOR]

Predators likely assess their risk of injury with regards to hunting different prey types, while deciding whether to initiate an attack or to avoid dangerous prey. Risk-taking is age-, stage- and state-dependent, and foraging theory predicts that juvenile predators, individuals of lower social rank, and less-experienced predators that are hungry are among those most likely to engage dangerous prey. In carnivores that optimally hunt prey larger than themselves, however, juveniles may also select for smaller, suboptimal prey as they refine their hunting skills. Thus, in the case of predators that exhibit age-specific prey selection, there may be multiple factors influencing decision-making about prey selection. We compared puma ( Puma concolor) predation on dangerous adult ungulates and safer juvenile ungulates, as well as two similar-sized rodent species: the more dangerous North American porcupine ( Erethizon dorsatum) and the more vulnerable American beaver ( Castor canadensis). We found that dispersing, subadult pumas with limited hunting experience and without territories avoided dangerous but optimally sized adult ungulates, and instead hunted dangerous, suboptimal porcupines more than resident, territorial adults. In contrast, there was no difference in puma predation on beavers between dispersers and residents. Small prey (e.g. not ungulates) formed a large portion of dispersing puma diets of both sexes, and this stage-dependent foraging pattern might be important in describing the ecology of the species, as well as in modeling potential dispersal habitat that could see puma expansion east in North America across hostile matrices where their primary prey has been reduced through anthropogenic effects. [ABSTRACT FROM AUTHOR]

Beaver impoundments modify the structure of river reaches and lead to changes in ecosystem function and biogeochemical processes. Here, we assessed the changes in dissolved organic matter (DOM) quality and the biodegradation patterns in a set of beaver systems across Sweden. As the effect of beaver impoundments might be transient and local, we compared DOM quality and biodegradability of both pond and upstream sections of differentially aged beaver systems. Newly established dams shifted the sources and DOM biodegradability patterns. In particular, humic-like DOM, most likely leached from surrounding soils, characterized upstream sections of new beaver impoundments. In contrast, autochthonous and processed compounds, with both higher biodegradation rates and a broader spectrum of reactivities, differentiated DOM in ponds. DOM in recently established ponds seemed to be more humic and less processed compared to older ponds, but system idiosyncrasies determined by catchment particularities influenced this ageing effect. [ABSTRACT FROM AUTHOR]