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Beavers (Castor canadensis) disappeared from drainages north of Yellowstone National Park in the mid-1900s because of trapping, a potential tularemia outbreak, and willow (Salix spp.) stand degradation by ungulates. Beavers were reintroduced in 1986 after a 40–yr absence with inventories of active-beaver structures completed each fall after reintroduction for 24 consecutive yr. We used this inventory to evaluate the expansion of beaver populations in a riparian environment recovering from past overuse by ungulates. Specifically, we investigated the density of active-beaver colonies and dams, the change in willow cover, and habitats associated with beaver expansion since reintroduction. Successful establishment and expansion of beavers indicate that sufficient resources were available to the population despite the suboptimal condition of riparian vegetation. Carrying capacity on third-order streams was reached approximately 14 yr after reintroduction (2000) with an average annual density of 1.33 (95th percentile = 1.23 − 1.44 active colonies/stream km) between 2000 and 2010. The average annual density of beaver dams during this time was 2.37 (2.04 − 2.71 active dams/stream km). Despite the beaver population being at carrying capacity in meadows since 2000, willow cover increased by 16% between 1981 and 2011. We speculate that beaver activities, together with reduced ungulate browsing from predation and habitat loss, combined to increase willow cover. Willow cover and height were positively associated with colony longevity, but numerous other influencing variables included secondary channels, sinuosity, stream depth, and sandbar width. Our results provide evidence that beaver reintroduction can be successful in riparian areas where willow stand condition is less than optimal and that beavers might ultimately improve willow condition. We suggest that reducing ungulate use of overgrazed riparian environments will facilitate the reestablishment of beaver populations. We also provide managers with habitats that should be identified in an environment targeted for reintroduction.

Non-point source (NPS) pollution remains high in many watersheds despite strategies aimed at reducing such pollution. Beaver (Castor canadensis) activity converts lotic systems to semi-lentic by impounding stream flow and trapping sediments, which have a high affinity for NPS pollutants such as nitrogen (N), phosphorus (P), and heavy metals. This study aimed to identify environmental conditions under which beaver ponds influence the fate and cycling of NPS pollutants. Dissolved and particulate nutrients were sampled upstream and downstream of three headwater beaver ponds differing in age and character through the summer season. Sedimentation rates and sediment concentrations of nutrients and metals were also determined. Results from this study suggest that beaver ponds can attenuate heavy metals at a rate 2 to 4 times greater than a riffle reach (p 0.05). Metal sequestration scaled with pond age and sediment organic matter content. The oldest and youngest ponds had no significant effect on dissolved nutrients (NO

Species distribution models and habitat suitability models (HSMs) have become a popular tool in the conservation of biodiversity. However, the ability to predict species spatial distributions at sites beyond the data source sites (i.e., spatial transferability) is critical for the applications of HSMs in the management and conservation of rare or endangered species. The main objective of our study was to assess the predictive performance and spatial transferability of expert opinion models (EOMs). To build EOMs, we identified through extensive literature reviews 17 key landscape variables to characterize habitat use by American beaver (Castor canadensis). We developed 31 pairwise opinion questions on the relative importance of the 17 selected habitat variables for an online survey in Qualtrics®. We used Saaty's analytical hierarchy process (AHP) and geospatial analysis to build EOMs for beaver. We tested the transferability of EOMs by assessing model predictive performance using the area under the curve (AUC > 0.7) in northcentral Mississippi and northern Alabama, USA. Thirty-five of 63 survey participants submitted complete, consistent surveys. Expert opinion models had fair predictive performance for beaver at the two study sites (AUC = 0.70–0.76). The fair predictive performance of EOM for the two sites, from which no opinion survey data were collected, indicated acceptable spatial transferability. The American beaver exhibits stable realized niche space throughout its geographic range, restricting habitat selection to open water bodies and associated wetlands, which may subsequently result in high transferability of HSMs.

The North American beaver (Castor canadensis) is an invasive species in southern Patagonia, introduced in 1946 as part of a program by the Argentine government to augment furbearers. Research focus has turned from inventorying the beaver's population and ecosystem impacts toward eradicating it from the region and restoring degraded areas. Successful restoration, however, requires a fuller determination of how beavers have altered physical landscape characteristics, and of what landscape features and biota need to be restored. Our goal was to identify changes to the physical landscape by invasive beaver. We analyzed channel and valley morphology in detail at one site in each of the three major forest zones occurring on the Argentine side of Tierra del Fuego's main island. We also assessed 48 additional sites across the three forest biomes on the island to identify a broader range of aquatic habitat occupied and modified by beaver. Beaver build dams with Nothofagus tree branches on streams, which triggered mineral sediment accretion processes in the riparian zone, but not in ways consistent with the beaver meadow theory and only at a few sites. At the majority of sites, beavers actively excavated peat and mineral sediment, moved thousands of cubic meters of sediment within their occupied landscapes and used it to build dams. Beaver were also common in fen ecosystems where pond formation inundated and drowned peat forming mosses and sedges, and triggered a massive invasion of exotic plant species. Results highlight that restoration of fen ecosystems is a previously unrecognized but pressing and challenging restoration need in addition to reforestation of Nothofagus riparian forests. We recommend that decision-makers include the full ecosystem diversity of the Fuegian landscape in their beaver eradiation and ecosystem restoration plans.

The North American beaver (Castor canadensis) is a classic ecosystem engineer, creating and expanding wetlands throughout their vast range. As important as their impacts on aquatic ecosystems, beaver as central place foragers restructure the surrounding forest community by their selective cutting of preferred woody species and size classes. These effects, which have been studied in several regions of North America, are still poorly understood within forests of the northeastern United States, where beaver populations are rebounding following regional extirpation. Here, beaver represent a key disturbance agent in a region where other drivers such as fire and timber cutting have been greatly reduced over the last century. Understanding their specific impacts on forest composition and structure is needed to manage these forests and their multiple ecosystem services. In this context, we assessed beaver foraging preferences throughout New York’s Adirondack State Park, a vast northern wooded region, to model their impacts on forest structure and composition. Across 19 sites distributed throughout the Park, beavers preferentially harvested stems

Borrow pits, dug by industry to provide substrate for infrastructure such as roads and well sites, are prevalent throughout the boreal forest of western Canada yet little is known about their use by wildlife. During field surveys in Rainbow Lake, Alberta, we found that beavers (Castor canadensis) used inundated borrow pits extensively for foraging and over wintering, suggesting that borrow pits increase beaver populations above their natural carrying capacity in industrial landscapes. We visited a random sample of 90 borrow pits in the field and categorized them as having active beaver lodges with caches (n = 16), inactive lodges (n = 13), cutting (n = 29), no activity (n = 13), or as not inundated or not a borrow pit (n = 19). We then used this sample to model where beavers established lodges versus where they were inactive or were only cutting. We found that borrow pits with active lodges had unique characteristics from other pits in our sample and were closer to streams, marshes, and swamps and had greater vegetation concealment from roads. These models can be used by managers to develop methods for increasing or decreasing the abundance of beavers living at borrow pits. Wildlife managers might want to use borrow pits to increase beaver abundance because of the positive effects beavers can have on ecosystems and because beavers are an important source of food for boreal carnivores. For example, we found that wolverines (Gulo gulo) used borrow pits as hunting grounds for beavers and one wolverine denned within a beaver lodge at a borrow pit. Conversely, managers might want to reduce beaver populations living at borrow pits because of the damage that beavers can cause to infrastructure and because subsidized beaver populations might alter predator-prey dynamics. To accomplish this, we suggest reducing available vegetation around borrow pits, isolating new borrow pits from natural beaver habitats, digging borrow pits where there is less chance of having surface water, filling in borrow pits with substrate, or not creating borrow pits and using a centralized gravel pit or mine for substrate.

Targeting human-inhabited islands for invasive species eradication campaigns layers social complexity on top of technical complexity. Attaining widespread support and cooperation for eradications requires programs designed to meet diverse stakeholder needs. The Tierra del Fuego archipelago serves as an informative case study and model for understanding and incorporating private landowner preferences into a proposed eradication program. We employed a human-centered approach to characterize landowner perceptions, preferences, and potential support for a large-scale initiative to eradicate the invasive North American beaver (Castor canadensis) from Tierra del Fuego. We used a factorial vignette survey to understand how attributes of an eradication program are related landowners' decisions to participate. Landowners rated four programs that randomly varied by contract length, required level of landowner involvement, institutional administrator, payment, social norms, and probability of a successful eradication. Landowners in Tierra del Fuego were generally more willing to participate under three conditions: (1) increased payments, (2) increased expectations of program success, and (3) low requirements for landowner involvement. Our results suggest that incorporating feedbacks into program design can increase public support, and that landowners in Tierra del Fuego may not express the same preference for autonomy that exists in other regions of the world. Understanding and incorporating stakeholder preferences, perceptions, and beliefs into management strategies is an ongoing challenge for conservation practitioners worldwide. The vignette survey approach provides a cost-effective, rapid, and scalable tool to document and incorporate local values into conservation program design. Programs built using a human-centered approach will complement landowners’ land-use objectives, increase cooperation, and ultimately improve conservation outcomes. Fil: Santo, Anna. Virginia Tech University; Estados Unidos Fil: Sorice, Michael G.. Advanced Conservation Strategies; Estados Unidos. Cornell University; Estados Unidos Fil: Donlan, C. Josh. Virginia Tech University; Estados Unidos Fil: Franck, Christopher T.. Virginia Tech University; Estados Unidos Fil: Anderson, Christopher Brian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Virginia Tech University; Estados Unidos. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; Argentina

Despite prevalent awareness of global amphibian declines, there is still little information on trends for many widespread species. To inform land managers of trends on protected landscapes and identify potential conservation strategies, we collected occurrence data for five wetland-breeding amphibian species in four national parks in the U.S. Rocky Mountains during 2002–2011. We used explicit dynamics models to estimate variation in annual occupancy, extinction, and colonization of wetlands according to summer drought and several biophysical characteristics (e.g., wetland size, elevation), including the influence of North American beaver (Castor canadensis). We found more declines in occupancy than increases, especially in Yellowstone and Grand Teton national parks (NP), where three of four species declined since 2002. However, most species in Rocky Mountain NP were too rare to include in our analysis, which likely reflects significant historical declines. Although beaver were uncommon, their creation or modification of wetlands was associated with higher colonization rates for 4 of 5 amphibian species, producing a 34% increase in occupancy in beaver-influenced wetlands compared to wetlands without beaver influence. Also, colonization rates and occupancy of boreal toads (Anaxyrus boreas) and Columbia spotted frogs (Rana luteiventris) were ⩾2 times higher in beaver-influenced wetlands. These strong relationships suggest management for beaver that fosters amphibian recovery could counter declines in some areas. Our data reinforce reports of widespread declines of formerly and currently common species, even in areas assumed to be protected from most forms of human disturbance, and demonstrate the close ecological association between beaver and wetland-dependent species.

a b s t r a c t Relocating American beavers (Castor canadensis) from unwanted sites to desirable sites (i.e., where damage exceeds stakeholder capacity) has been posited as a method to enhance in-stream habitat for salmonids in the Pacific Northwest region of the US; however, no studies have evaluated this method. From September–December 2011, we trapped and relocated 38 nuisance beavers using guidelines available to Oregon landowners. Release sites were selected from models that identified high values of beaver dam habitat suitability and where dams would increase intrinsic potential of coho salmon (Oncorhynchus kisutch). Mean distance moved from release sites within 16 weeks post-release was 3.3 ±0.2 (SE) stream km (max 29.2 km). Mean survival rate for relocated beavers was 0.47 ±0.12 (95% CI: 0.26–0.69) for 16 weeks post-release, while the probabilities of an individual dying to predation or disease/illness during the same period were 0.26 (95% CI: 0.09–0.43) and 0.16 (95% CI: 0.01–0.30), respectively. Dam construction was limited and ephemeral due to winter high flows, providing no in-stream habitat for coho. We conclude beaver relocation options available to landowners in Oregon may not be an effective option for stream restoration in coastal forestlands due to infrequent dam occurrence and short dam longevity.

Beavers are ecosystem engineers which are capable to facilitate many groups of organisms. However, their facilitation of mammals has been little studied. We applied two methods, camera trapping and snow track survey to investigate the facilitation of a mammalian community by the ecosystem engineering of the American beaver (Castor canadensis) in a boreal setting. We found that both mammalian species richness (83% increase) and occurrence (12% increase) were significantly higher in beaver patches than in the controls. Of individual species, the moose (Alces alces) used beaver patches more during both the ice-free season and winter. The Eurasian otter (Lutra lutra), the pine marten (Martes martes) and the least weasel (Mustela nivalis) made more use of beaver sites during the winter. Our study highlights the role of ecosystem engineers in promoting species richness and abundance, especially in areas of relatively low productivity. Wetlands and their species have been in drastic decline during the past century, and promoting facilitative ecosystem engineering by beaver is feasible in habitat conservation or restoration. Beaver engineering may be especially valuable in landscapes artificially deficient in wetlands. (c) 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Of the many types of barriers to water flow, beaver dams are among the smallest, typically lasting less than a decade and rarely exceeding 1.5 m in height. They are also among the most frequent and common obstructions in rivers, with a density often exceeding ten dams per km, a frequency of construction within a given network on a time scale of years, and a historic extent covering most of North America. Past quantification of the geomorphologic impact of beaver dams has primarily been limited to local impacts within individual impoundments and is of limited geographic scope. To assess the impact of beaver dams at larger scales, this study examines channel shape and sediment distribution in thirty river reaches in northeastern Connecticut, U.S.A. The study reaches fall within the broader categories of impounded and free-flowing segments, leaving a third segment class of beaver meadows requiring additional study. Each of the study reaches were classified at the reach scale as free-flowing, valley-wide beaver pond, in-channel beaver pond, and downstream of beaver dam. The bankfull channel width to depth ratios and channel widths normalized by watershed area vary significantly across the study reach classes. Additionally, reaches modified by beaver dams have finer sediment distributions. This paper provides the first quantitative geomorphic descriptions of the in-channel beaver pond and reaches downstream of beaver dams. Given the different channel shapes and sediment distributions, we infer that geomorphic processes are longitudinally decoupled by these frequent barriers that control local base level. These barriers generate heterogeneity within a river network by greatly increasing the range of channel morphology and by generating patches controlled by different processes. Therefore, in spite of the small size of individual beaver dams, the cumulative effect of multiple dams has the potential to modify processes at larger spatial scales. To improve assessment of the larger-scale impacts, we propose a hierarchical classification scheme based on discontinuities, place the reach classes of this study within that scheme, and suggest that further research should continue investigation of discontinuity at the network scale and quantification of the cumulative impacts.

The papillomaviruses comprise a large group of viruses that cause proliferations of the stratified squamous epithelium of skin and mucosa in a variety of animals. An earlier report identified a novel papillomavirus of the North American beaver, Castor canadensis (CcanPV1) that was associated with cutaneous exophytic lesions. In the current study, we determined the sequence of the complete 7435 basepair genome of CcanPV1. The genome contains an Upstream Regulatory Region located between the end of L1 and the start of E6, and seven canonical papillomavirus open reading frames encoding five early (E6, E7, E1, E2, and E4) and two late (L2 and L1) proteins. No E5 open reading frame was detected. Phylogenetic analysis of the CcanPV1 genome places the virus between the genera Kappapapillomavirus and Mupapillomavirus. Analyses of the papillomavirus genomes detected in different species of the order Rodentia indicate these viruses do not form a monophyletic clade.

Urban North American beaver (Castor canadensis) damage of trees and saplings was compared between shore forests and forests uphill of macadam, wood chip, and raised wood board human pathways used daily in Radnor Lake State Natural Area, Nashville, TN. Also, comparisons of beaver damage were made between shore forests and forests uphill of bare earth deer paths used less than once a month by humans and the forests were on 5% and 30% slopes. Means, standard deviations, and t-tests (P ≤ 0.05) were calculated for percent beaver damage, which included undamaged stems, beaver-cut stems, and beaver-cut stumps. Significant differences in beaver damage of trees and saplings were found between forests uphill of the human pathways used daily and the respective shore forests. Beaver damage of trees and saplings was not significantly different between the shore forests and forests uphill of the deer paths used less than once a month by humans for the 5% slope forest; however, the differences were significant for the 30% slope forest. Beaver damage of trees and saplings was significantly greater in the uphill of the deer paths forests than the uphill of the human pathways forests for comparable slope forests. Human scent on the pathways used daily made of macadam, wood chips, and raised wood boards was interpreted to be the barrier sensed by beavers to not cross over or under the human pathways to damage trees and saplings. This research suggests utilizing human pathways as an odor fence to spatially limit beaver damage, which provides a whole forest management alternative to individual tree protection for management of beaver damage in the urban forest.

In many settings wildlife can be a significant source of fecal pathogen input into surface water. The North American beaver (Castor canadensis) is a zoonotic reservoir for several human pathogens including Cryptosporidium spp. and Giardia spp. In order to specifically detect fecal pollution by beavers, we have developed and validated a beaver-specific Bacteroidales marker, designated Beapol01, based on the 16S rRNA gene. The marker is suitable for quantifying pollution using real-time PCR. The specificity and sensitivity of the marker was excellent, Beaver signal was detected in water of a mixed-activity watershed harbouring this rodent. Overall, Beapol01 will be useful for a better understanding of fecal source inputs in drainage basins inhabited by the beaver.

Body temperature has a major influence on the physiological processes, growth, reproductive output, and overall survival of ectotherms. When a habitat is altered as a result of natural or anthropogenic influences, the available temperatures in the habitat can change, thus affecting an animal's ability to thermoregulate. We studied thermoregulation in response to habitat change in a population of spotted turtles ( Clemmys guttata ) in Southern Ontario, Canada. Historically, the study site was ditched to draw down water levels to facilitate peat mining, and the resulting drainage ditches were the only habitat containing surface water and turtles were restricted to these drains. Recent colonization of the site by beaver ( Castor canadensis ) caused increases in water level and water surface area. We followed spotted turtles ( N =16) outfitted with radio transmitters and iButtons to estimate body temperatures ( T b ) continuously throughout the active season post-flooding. Turtle models outfitted with iButtons ( N =50) were deployed in the nine available habitat types to record environmental temperatures ( T e ). Turtles ( N =13) were tested in a thermal gradient under laboratory conditions to determine preferred body temperature range ( T set ). The T set for the population ranged from 20 °C to 26 °C. In the field, T b was within the T set range 28% of the time from March to October, and 67% of the time from July to August. Efficiency of thermoregulation was calculated to be highest in July and August. The habitat type with the highest thermal quality was the shallow flooded zone created by beaver damming, and the habitat with the lowest thermal quality was the drain bottom, the drains being the only aquatic habitat available prior to flooding. This study confirms that beaver flooding provided a wide variety of preferable thermal opportunities for spotted turtles. Further investigation is needed to determine the effects of flooding on spotted turtle thermoregulation during nesting and hibernation.

Historically the wolf (Canis lupus) was hated and extirpated from most of the contiguous United States. The federal Endangered Species Act fostered wolf protection and reintroduction which improved the species’ image. Wolf populations reached biological recovery in the Northern Rocky Mountains and upper Midwest, and the animal has been delisted from the Endangered Species List in those areas. Numerous studies in National Parks suggest that wolves, through trophic cascades, have caused ecosystems to change in ways many people consider positive. Several studies have been conducted in Yellowstone National Park where wolf interactions with their prey, primarily elk (Cervus elaphus), are thought to have caused reduction of numbers or changes in movements and behavior. Some workers consider the latter changes to have led to a behaviorally-mediated trophic cascade. Either the elk reduction or the behavioral changes are hypothesized to have fostered growth in browse, primarily willows (Salix spp.) and aspen (Populus spp.), and that growth has resulted in increased beavers (Castor Canadensis), songbirds, and hydrologic changes. The wolf’s image thus has gained an iconic cachet. However, later research challenges several earlier studies’ findings such that earlier conclusions are now controversial, especially those related to causes of browse regrowth. In any case, any such cascading effects of wolves found in National Parks would have little relevance to most of the wolf range because of overriding anthropogenic influences there on wolves, prey, vegetation, and other parts of the food web. The wolf is neither a saint nor a sinner except to those who want to make it so.

The sub-Antarctic biome of South America is the world's southernmost forested ecosystem and one of the last remaining wilderness areas on the planet. Nonetheless, the region confronts various anthropogenic environmental impacts, such as the invasive North American beaver (Castor canadensis) and timber harvesting, particularly in stands of Nothofagus pumilio. Both of these disturbances can affect terrestrial and aquatic systems. To understand the influence and relative importance of these disturbances on sub-Antarctic watersheds, we characterized in-stream and riparian habitat conditions (pH, dissolved oxygen, conductivity, temperature, stream size, distance to riparian forest, bank slope, substrate heterogeneity, benthic organic matter) and benthic macroinvertebrate community structure (density, richness, diversity, evenness) and function (biomass, functional feeding group percent) in 19 streams on Tierra del Fuego Island. To explain the effects of beaver invasion and timber harvesting, we compared these physical and biotic variables among four habitat types: (a) beaver meadows, (b) shelterwood cut harvested areas without forested riparian zones, (c) variable retention harvested areas with riparian buffers, and (d) unmanaged old-growth primary forests. Most habitat variables were similar at all sites, except for dissolved oxygen (significantly higher in streams from old-growth primary forests). Benthic communities in beaver meadows had significantly lower diversity, compared to streams of unmanaged old-growth primary forests, and managed sites presented intermediate values between the two. Functionally, the benthic community in beaver meadows displayed a reduction of all functional feeding groups except collector-gatherers; again variable retention harvested areas with riparian buffers were similar to unmanaged old-growth primary forest streams, while shelterwood cut harvested areas occupied an intermediate position. These results indicated that current forestry practices that include both variable retention and legally mandated riparian forested buffers may be effective in mitigating impacts on stream benthic communities. Finally, these data demonstrated that C. canadensis invasion was a relatively larger impact on these streams than well-managed forestry practices.

The management of biological invasions is a complex and often controversial issue reflecting a diversity of values. Research and public policy on invasive species have concentrated on their ecological and economic impact, most frequently overlooking the social component. In this paper we examined the public perceptions of invasive species of high conservation concern in the Cape Horn Biosphere Reserve, Chile, for which management plans are forming: the American mink (Neovison vison); and, the North American beaver (Castor canadensis). Two native species served as counter-examples, the guanaco (Lama guanicoe) and the upland goose (Chloephaga picta). Qualitative semi-structured interviews covered three areas: conceptualisation and knowledge of invasive species; values associated with invasive and native species; and acceptance of control measures. We found differentiated knowledge and high awareness of invasive species among the public. Interviewees attributed utilitarian, aesthetic, and humanistic values to all four species; however, negativistic values were attributed only to invasive species, and moralistic values only to native species. Our results further revealed key issues explaining tolerance towards invasive species, and different positions of acceptance for management. To include a broader public participation in the design and management of responses to biological invasions we suggest: (1) considering local knowledge as a source of information, and vice versa, providing the public with scientific information; (2) evaluating the tolerance level towards invasive species and negotiating conflicting values; (3) clarifying the perspectives of economic income through invasive species management; and, (4) employing compromises on the basis of suggestions from the public.

Summary The European beaver ( Castor fiber ) was recently reintroduced to Belgium, after an absence of more than 150 years; around 120 beaver dam systems have been established. In Europe, few studies consider the hydrological effects of those dams, and the spatial scale larger than that of one beaver pond system has not been addressed at all. This research focuses on the hydrological effects of a series of six beaver dams on the Chevral R., a second order tributary of the Ourthe Orientale R. in a forested area of the Ardennes. Thereby, also the Ourthe Orientale sub-basin itself was taken into account, being the area with probably the highest density of beaver dams in Belgium. The main research questions regarded: (1) the extent to which discharge peaks are reduced at the very location and well downstream of beaver dams and (2) the impact of the beaver dams on low flows. The first approach consisted of a temporal analysis of the Ourthe Orientale discharge and precipitation data for the periods 1978–2003 (before) and 2004–2009 (after the establishment of beaver dams in the sub-basin). The second study determined the in situ impact of the beaver dams: discharges were measured (September 2009–March 2010) upstream as well as downstream of the 0.52 ha beaver dam system on the Chevral river, and changes in water level within the system of six dams were monitored. Our findings indicate that there is a significant lowering of discharge peaks in the downstream river reaches due to the effect of the beaver dams. The temporal analysis of the Ourthe Orientale sub-basin shows an increase in the recurrence interval for major floods; for instance, the recurrence interval of a reference flood of 60 m 3 s −1 increased from 3.4 years to 5.6 years since the establishment of the beaver dams. At the scale of the Chevral beaver dams’ site, we measured that the dams top off the peak flows, in addition delaying them by approximately 1 day. There are also increased low flows: Q 355 (i.e. the discharge exceeded 355 days in a year) of the Ourthe Orientale was 0.6 (±0.15) m 3 s −1 before beaver dam installation and 0.88 (±0.52) m 3 s −1 thereafter. These findings agree with studies that suggest natural measures for flood control at the level of small mountain streams instead or in complement of building large anthropogenic constructions. Nevertheless, more studies are needed to assess the effectiveness of beaver dams in flood mitigation at the scale of sub-basins.

Herbivores, such as beavers (Castor canadensis) and ungulates, can dramatically alter the species composition and structure of riparian vegetation communities. We examined how four different levels of beaver presence and ungulate density influenced the structure and composition of riparian vegetation communities in the mixed-wood boreal region of east-central Alberta, Canada. Beavers, as central-place foragers, focus on similar species utilized by the six ungulate species in our study area. However, we found that vegetation responded differently relative to the percent cover and heights of emergent, shrub, herbaceous dicots, and tree species depending on the varying combinations of beaver presence and ungulate densities. There was an obvious negative effect of ungulate herbivory on shrub heights and cover; however, we were unable to find any significant effects on the overall composition and structure of vegetation communities that were exclusively related to beaver activities. In areas with no beavers and lower ungulate densities there was a positive growth response in preferred species (e.g., Salix spp., Prunus spp.), which clearly demonstrated the degree of combined influence that these herbivores have on riparian communities. In these areas, Salix spp. was four times shorter than in areas where beavers were not present and ungulate densities were lower. In addition percent cover was lowest for emergent vegetation and herbaceous dicots in areas with higher ungulate densities. Many studies focus on single-species effects on forage resources, yet our research shows that the study of combined effects of multiple herbivores can provide a new insight into these complex systems.

Beaver–willow ( Castor - Salix ) communities are a unique and vital component of healthy wetlands throughout the Holarctic region. Beaver selectively forage willow to provide fresh food, stored winter food, and construction material. The effects of this complex foraging behavior on the structure and function of willow communities is poorly understood. Simulation modeling may help ecologists understand these complex interactions. In this study, a modified version of the SAVANNA ecosystem model was developed to better understand how beaver foraging affects the structure and function of a willow community in a simulated riparian ecosystem in Rocky Mountain National Park, Colorado (RMNP). The model represents willow in terms of plant and stem dynamics and beaver foraging in terms of the quantity and quality of stems cut to meet the energetic and life history requirements of beaver. Given a site where all stems were equally available, the model suggested a simulated beaver family of 2 adults, 2 yearlings, and 2 kits required a minimum of 4 ha of willow (containing about10 stems m −2 ) to persist in a steady-state condition. Beaver created a willow community where the annual net primary productivity (ANPP) was 2 times higher and plant architecture was more diverse than the willow community without beaver. Beaver foraging created a plant architecture dominated by medium size willow plants, which likely explains how beaver can increase ANPP. Long-term simulations suggested that woody biomass stabilized at similar values even though availability differed greatly at initial condition. Simulations also suggested that willow ANPP increased across a range of beaver densities until beaver became food limited. Thus, selective foraging by beaver increased productivity, decreased biomass, and increased structural heterogeneity in a simulated willow community.

Shallow open water wetlands provide critical habitat for numerous species, yet they have become increasingly vulnerable to drought and warming temperatures and are often reduced in size and depth or disappear during drought. We examined how temperature, precipitation and beaver (Castor canadensis) activity influenced the area of open water in wetlands over a 54-year period in the mixed-wood boreal region of east-central Alberta, Canada. This entire glacial landscape with intermittently connected drainage patterns and shallow wetland lakes with few streams lost all beaver in the 19th century, with beaver returning to the study area in 1954. We assessed the area of open water in wetlands using 12 aerial photo mosaics from 1948 to 2002, which covered wet and dry periods, when beaver were absent on the landscape to a time when they had become well established. The number of active beaver lodges explained over 80% of the variability in the area of open water during that period. Temperature, precipitation and climatic variables were much less important than beaver in maintaining open water areas. In addition, during wet and dry years, the presence of beaver was associated with a 9-fold increase in open water area when compared to a period when beaver were absent from those same sites. Thus, beaver have a dramatic influence on the creation and maintenance of wetlands even during extreme drought. Given the important role of beaver in wetland preservation and in light of a drying climate in this region, their removal should be considered a wetland disturbance that should be avoided.

Concentrated herbivory by elk (Cervus elaphus) can degrade vegetative communities and alter ecosystem processes. Areas severely damaged by elk are commonly protected with woven wire fence, which can exclude other animals. Complete exclusion and prevention of large mammal herbivory might not always be necessary to restore vegetative communities. We designed and evaluated a simple fence that excluded elk, but maintained access for deer and other species. We enclosed a 1-ha stand of quaking aspen (Populus tremuloides Michaux) with our fence in an area with a high density of elk. We monitored effectiveness of the fence with trackplots, animal-activated cameras, and changes in aspen stem height and density. We documented only 1 elk within the exclosure in 2 years of monitoring. Mammals that used the exclosure included beaver (Castor canadensis), black bear (Ursus americanus), bobcat (Lynx rufus), coyote (Canis latrans), deer (Odocoileus spp.), mountain lion (Puma concolor), raccoon (Procyon lotor), red fox (Vulpes vulpes), and lagomorph (Leporidae). After 1 year of protection, mean aspen stem height increased 14.5 cm more inside the exclosure than outside, but stem density in the exclosure changed little compared to outside. Our fence design effectively excluded elk and has potential for protecting a variety of resources.

Fire, flooding, herbivory, and the effects of climate are all topical issues for today's land managers. Effective resource management requires a balance among these processes, which in turn, requires a better understanding of their interactions. Beaver (Castor canadensis) are strong colonizers and have been successfully reintroduced to much of their former range. Prescribed fire has also been introduced in many areas as a management tool to restore ecological function. Resource managers have often assumed fire would also benefit non-target species like beaver; however, its effect on beaver has not been well studied. In this study, part of a broader project in Elk Island National Park, Canada, we examine the effect of prescribed fire on beaver lodge occupancy in the context of high ungulate populations. Elk Island National Park has an active beaver population, high ungulate densities, and a well-established prescribed fire program. We examine whether frequency, size, and timing of burns influence beaver lodge occupancy and the establishment of new lodges. Since 1979, over 51% of the park (99.3 km2) has been burned with prescribed fire. By comparing lodge occupancy over a period prior to and after a series of prescribed burns, we analyzed beaver occupancy rates pre- and post-burn. Our results show that repeated burning dramatically decreases beaver lodge occupancy, and that even after one burn the number of active colonies declines and does not recover to pre-fire populations. Especially when combined with drought and herbivory, prescribed fire does not improve beaver habitat.

We explored the use of beaver (Castor canadensis) as a surrogate species for amphibian conservation on small (1st–4th-order) streams in the Boreal Foothills of west-central Alberta. Anuran call surveys indicated that beaver create breeding habitat for the boreal chorus frog (Pseudacris maculata), wood frog (Rana sylvatica) and western toad (Bufo boreas). No calling males of any species were recorded on unobstructed streams. Wood frog, the most abundant species, exhibited high rates of juvenile recruitment on beaver ponds. Pitfall traps captured more wood frogs on beaver ponds versus unobstructed streams, and most individuals (84%) were young-of-year. Abundance of young-of-year was strongly correlated with percent landscape occupied by beaver ponds indicating that anurans captured along streams originated in beaver ponds. Based on a novel combination of a digital elevation model and aerial photographs examined with GIS, statistical models showed that the probability of beaver pond occurrence on streams was positively associated with stream order and dependent on the interacting effects of distance to nearest forestry cutblock and availability of beaver foods (Populus spp.). We propose that the distribution and abundance of beaver ponds could be determined over large areas quickly and inexpensively by remote sensing and used to identify and monitor amphibian habitat, and possibly, populations. This work establishes the pre-eminence of beaver-created wetlands as amphibian habitat in the Boreal Foothills and that the incorporation of dam-building patterns into forest management strategies could aid amphibian conservation.

Periradicular bands are incremental structures seen on the external dentin surfaces of rodent incisors. They correspond to circadian developmental rhythms in dentin growth and provide a record of the growth rate of the incisor along its longitudinal axis. In the present study, we investigate the relationship between daily environmental temperatures and longitudinal growth rates of incisors in 40 Recent beavers ( Castor canadensis ). We also look for trends in growth rates that reflect precipitation or photoperiod. The goal is to explore the potential of using longitudinal growth data as indicators of seasonality in past environments. The sample consists of upper and lower incisors of fall-harvested beavers and upper incisors of winter-harvested beavers with known dates of death. All distances between sequential periradicular bands were measured using a dissecting microscope fitted with an ocular micrometer. All increments for each individual were matched to corresponding dates of formation. Records of daily temperatures, precipitation, and photoperiod corresponding to the locality and period of growth represented by the teeth were obtained from the National Weather Service. Time series for both dental increments and temperature were smoothed using nonparametric regression to partition “primary” (seasonal or long-term) and “secondary” (daily or short-term) signals. Upper and lower incisors differ in their primary signals in that uppers exhibit a marked decline in growth rate during the late summer and early fall, leveling off in the late fall. This trend roughly parallels seasonal decreases in temperature, precipitation, and photoperiod, although the decline in growth rate begins while the weather is still warm (in late summer). In contrast, lower incisors show only a very weak seasonal trend in growth rate. Analysis of residuals from the trend lines reveals only a weak association between daily growth rate and both daily temperature changes and precipitation. The results suggest that longitudinal growth rates in upper incisors may be used to estimate season of death in fossil rodents.

Historically, forests in the northeastern United States were disturbed by fire, wind, Native American agriculture, flooding, and beavers (Castor canadensis). Of these, wind and beavers are now the only sources of natural disturbance. Most disturbance-dependent species, especially birds, are declining throughout the region whereas species affiliated with mature forests are generally increasing or maintaining populations. Disturbance must be simulated for conservation of early-successional species, many of which are habitat specialists compared to those associated with mature forests. Both the maintenance of old fields and forest regeneration are needed to conserve brushland species. Regenerating forest habitats are more ephemeral than other woody early-successional habitats. The types and amounts of early-successional habitats created depend on the silvicultural system used, patch size selected, time between regeneration cuts, and rotation age. We recommend that group selection and patch cuts should be at least 0.8 ha, and patches should be generated approximately every 10–15 years depending on site quality. Regeneration of intolerant and mid-tolerant tree species should be increased or maintained in managed stands. Also, frost pockets, unstocked, or poorly-stocked stands can provide opportunities to increase the proportion of early-successional habitats in managed forests.

Caddo Lake, USA, a Ramsar Wetland of International Importance, is a lacustrine wetland complex consisting of stands of flooded baldcypress intermixed with open water and emergent wetland habitats. Recently, concern has been expressed over a perceived increase in the beaver population and the impact of beaver on the long-term sustainability of the baldcypress ecosystem. We used intensive beaver lodge surveys to determine the distribution and relative abundance of beaver and the amount, type, and distribution of beaver damage to mature trees and seedlings at Caddo Lake. A total of 229 lodges were located with a combination of aerial and boat/ground surveys. Most lodges were located in open water and edge habitats. About 95% of the lodges were occupied by beaver or nutria. Some form of damage was exhibited by one or more trees near 85% of the lodges. Intensive damage assessments around 35 lodges indicated that most damage to trees, baldcypress in particular, was restricted to peeling or stripping of bark which is believed to have minimal effect on tree survival. Surveys of regeneration indicated that baldcypress seedlings were very abundant; however, over 99.9% were less than 30 cm tall. The lack of recruitment into the larger size classes appears to be a result of high stand densities and water management practices. At this time, the young age and density of the baldcypress forests suggest that recruitment is not a major concern and herbivore damage appears to be having a minimal effect on the forest.

By repeatedly presenting an alien scent to territory-owning beavers, Castor canadensis, we tested two competing hypotheses about the function of scent marking: scent fence and scent matching. The scent-fence hypothesis predicts that territory owners should respond increasingly strongly over time towards a recurrent alien scent because of the ineffectiveness of previous responses. The scent-matching hypothesis predicts that the intensity of response should be the same or decrease because, without the presence of the intruding signaller coupled with the chemical signal, the presence of the scent itself does not advertise the ownership of a territory. The response level of resident beaver families was stable to strangers' anal gland secretions (AGSs) and decreased to strangers' castoreum during a period of 6 days. These results support the scent-matching hypothesis but not the scent-fence hypothesis. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

The δ18O of Canadian beaver (Castor canadensis) teeth should reflect variations in the isotopic composition of the water in which the beavers live, as their incisors grow rapidly and continuously. We observe seasonal variations in phosphate δ18O using samples of enamel taken along the length of single teeth. In the spring the δ18O of the enamel being deposited gradually declines, reflecting a retarded input of δ18O depleted winter water. After mid-year, enamel δ18O is higher than average (as represented by the δ18O of bone phosphate from the same animal) and passes through a maximum in late summer or early fall. Overall, the amplitude of seasonal excursions in enamel δ18O (4‰) is much smaller than the expected summer-winter range in the δ18O of meteoric water (> 10‰). This is because hydrologic mixing processes, gradual admixing of environmental water with beaver body water, long-term plant growth, and oxygen inputs of relatively constant value (particularly atmospheric oxygen) tend to even out summer-winter differences in the δ18O of oxygen inputs to the beaver. The δ18O of bone from adult beavers was uniform at 11.9 ± 0.5‰ over the study area. Analyses of a Sangamon age giant beaver (Castoroides ohioensis) incisor from Hopwood Farm, Illinois, show a slightly larger 5.5‰ seasonal cycle of δ18O with an average enamel δ18O of 18‰. This suggests that average temperatures were warmer during the Sangamon than today and that seasonal temperature differences and/or relative humidity variations were larger.

Site-specific differences in fatty acid composition of adipose tissues from Finnish beavers (Castor canadensis and Castor fiber) and muskrats (Ondatra zibethicus) were studied by gas liquid chromatography. In the total lipids of heterothermic extremities the proportions of potentially endogenous (delta 9-desaturated) monoenoic fatty acids were 1.5-fold and those of the saturated fatty acids 0.5-fold the proportions of subcutaneous or inner depots. Thus the role of delta 9-desaturation in the biochemical adaptation of the extremity tissues is discussed. Dietary polyunsaturated fatty acids, with the exception of 18:3 omega 3 in the beavers, did not accumulate selectively in the extremity tissues. The liver of the muskrat (which also eats fish and mussels) contained high proportions of 22:6 omega 3, which was a minor component in the beaver (exclusively a herbivore).

Foods indigenous to two communities of the Sahtu Dene/Metis of the Northwest Territories, Canada, are reported for their use frequency and for their composition for moisture, protein, fat, ash, computed carbohydrate and energy, and for the mineral elements Ca, P, Na, K, Fe, Zn, Cu, Mg, and Mn. Summary data are also reported for the contents of Cr, Co, Ba, Mo, Sn, Sr, Ti, Ni, Si, and V. This is the first comprehensive report of this group of nutrients in the primary foods of the Sahtu Dene/Metis traditional food system, and it is the first report for many nutrients in several of the foods. New information is presented for several land mammals, birds, fish, and berries. The species most frequently reported to be used are caribou ( Rangifer tarandus ), moose ( Alces alces ), beaver ( Castor canadensis ), muskrat ( Ondatra zibethicus ), Canada goose ( Branta canadensis ), burbot ( Lota lota ), whitefish ( Coregonus clupeaformis ), black scoter ( Melanitta nigra ), ptarmigan ( Lagopus sp. ), and berries ( Vaccinium myrtilloides, Ribes oxyancanthoides, Vaccinium vitis-idaea, etc.) Data on several other species are presented.

Radionuclide levels were measured in tissues, gut contents, diet items, and water at site of capture, of adult beavers from the Serpent River drainage basin which contains U tailings at Elliot Lake, Ontario, and from nearby control sites. Levels of (226)Ra in beaver bone, muscle and kidney were highest in animals from locations close to U tailings; liver levels did not vary by site. Environmental (226)Ra levels were within ranges previously reported at these or similar locations elsewhere; levels in beaver gut contents reflected levels in diet items. Concentration ratios exceeded unity only between some vegetation items and beaver bone at the Elliot Lake site and were less than 0.19 between vegetation and other tissues. In two beavers with tissue levels of (226)Ra higher than other sampled, neither (232)Th nor (230)Th were detected in bone, muscle or liver tissues. U-238 was measurable in bone, muscle and liver, (228)Th in bone, (210)Po bone, muscle and liver; and (210)Pb was measurable only in bone. Estimated yearly intakes of radionuclides by people eating beavers were calculated to be below current allowable levels set by the Canadian regulatory authorities.

1. 1. The skin surface lipids of 46 species of mammals were extracted from fur samples with chloroform and analysed by thin layer chromatography. 2. 2. Within the families Canidae, Bovidae and Equidae, there was much similarity in composition of the surface lipids among species. In other families, including Procyonidae, Sciuridae and Mustelidae, there were considerable differences among related species. 3. 3. Between families there were profound differences in surface lipid composition, such that quite different classes of lipids were present. 4. 4. Only three species, the otter ( Lutra canadensis ), beaver ( Castor canadensis ) and kinkajou ( Potos flavus ) produce surface lipids containing squalene, one of the principal constituents of human sebum.

1. 1. Ca 2+ and Mg 2+ stimulated ATPase activities were indistinguishable according to their subcellular distribution. 2. 2. Ca 2+ and Mg 2+ ATPase activities were chiefly associated with the microsomal and mitochondrial fractions. 3. 3. Ouabain did not inhibit Ca 2+ ATPase activity. 4. 4. The Ca 2+ and M 2+ activated ADPase associated with the supernatant fraction may be largely attributed to myokinase and non-specific phosphatase activities. 5. 5. Ca 2+ and Mg 2+ activated ADPases, separate from the action of myokinase and non-specific phosphatases, were associated chiefly with the microsomal and mitochondrial fractions.

Scent marking by the beaver (Castor canadensis) has commonly been ascribed a function in territorial maintenance. This study examined the placement of scent mounds by beaver colonies, the frequency of scent mounds constructed by colonies with a low probability of encountering conspecifics versus colonies with a high probability of such encounters, and the responses of individual animals to castor gland homogenate from donor animals of known sex and age. Scent mounds are constructed most often in areas of high colony activity, and colonies with a high probability of encountering transient conspecifics construct significantly more mounds. Behavioral data suggest that information regarding sexual status may be transmitted by scent mounds. The data do not support a territorial maintenance function for scent marking in the beaver.

Sexual differences in social and construction behaviours of Canadian beavers ( Castor canadensis ) were studied in the field in central Massachusetts. The colony was organized around the adult female. She emerged from the lodge first 93 per cent of the time, tail-slapped twice as frequently as the adult male, was the alpha member of the family in dominance encounters and elicited more calls from other beavers than any other animal. Tail-slapping by females was significantly more effective in causing beavers to move to deep water than tail-slaps by males. The adult female led the family in lodge maintenance, food cache building and dam maintenance. The adult male performed close dam inspection twice as often as the adult female.

SUMMARY Fatal paralysis has occurred in beavers in the Dublin Zoological Gardens for some years, and it has been found impossible to raise this species to maturity. Immature worms or larvae which are probably ascarids appear to be the cause of a focal malacia of the brain and almost certainly account for the neuroparalytic signs. We have no idea what are the natural hosts of these parasites. The case adds to a growing list of diseases which are caused by helminth parasites migrating to the central nervous system of a great variety of mammalian hosts.