Article

The general ecology of beavers (Castor spp.), as related to their influence on stream ecosystems and riparian habitats, and the subsequent effects on fish - A review

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

page 439 Abstract The Eurasian and North American beavers are similar in their ecological requirements, and require water deep enough to cover the entrance to their lodge or burrow. A food cache is often built next to the lodge or burrow, except in some southern areas. On small streams (up to fourth order) dams are frequently built to create an impoundment, generally on low gradient streams, although at high population densities dams may be built on steeper gradient streams. On large rivers or in lakes, simply a lodge with its food cache may be built. The beaver is a keystone riparian species in that the landscape can be considerably altered by its activities and a new ecosystem created. The stream above a dam changes from lotic to lentic conditions. There are hydrological, temperature and chemical changes, depending on types of dams and locations. Although the invertebrates may be fewer per unit area, total number of organisms increases, and diversity increases as the pond ages. In cool, small order streams, the impoundments provide better habitat for large trout, possibly creating angling opportunities. However, at sites

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Beaver impoundments recharge ground water by elevating the water table, resulting in an increase in riparian habitat. The effects of impoundments include changing the temperature regime, which becomes more stabilized (Collen and Gibson 2001, Majerova et al. 2015, Weber et al. 2017), but varies significantly by region and site characteristics (Collen and Gibson 2001). ...
... Beaver impoundments recharge ground water by elevating the water table, resulting in an increase in riparian habitat. The effects of impoundments include changing the temperature regime, which becomes more stabilized (Collen and Gibson 2001, Majerova et al. 2015, Weber et al. 2017), but varies significantly by region and site characteristics (Collen and Gibson 2001). ...
... Creek and food sources for beaver. Where available, aspen (Populus tremuloides) is the preferred woody species used by beaver (Collen and Gibson 2001). In the absence of aspen, beaver will show varying preferences, depending on the availability of species at the sites and include cottonwood (Populus spp.), willows (Salix spp.), alder (Alnus spp), and birch (Betula spp) (Collen andGibson 2001, Pollock et al. 2014). ...
Technical Report
Historically, beavers and beaver dams were an important component of dryland riparian systems in the western US and exerted an extraordinary influence on these systems. At the time of Euroamerican settlement of the Eagle Valley, beavers were present along main Daly Creek. Land management activities including diverting water for irrigation, channelizing, and removal of riparian vegetation for agricultural purposes and cattle grazing likely changed the historic multi-thread channel system at Daly Creek into a single-thread channel. Daly Creek was divided in 3 reaches based on past legacy of farming and grazing to evaluate system responses: 1) Lower Daly Creek (1.2 miles [1.9 km]), 2) Middle Daly Creek (5.9 miles [9.5 km]), and 3) Upper Daly Creek (2 miles [3.2 km]). Given the key role that beaver play in the recovery of Daly Creek, beaver dam and pond surveys started in 2009 when beaver activity was first noted as part of a larger study to assess (passive) riparian recovery. Specific objectives were to: 1) annually locate all beaver dams, 2) collect information on location, and physical characteristics of dams (i.e., dam height and length, crossing of stream or partial dam), and 3) survey and map beaver ponds on at least a 2-year interval. From 2009 through 2018, surveys were conducted annually, although no beaver activity was noted in 2010-2012. In 2009, 2013 and 2014 spring surveys were conducted. In 2014 and following years, fall surveys were conducted when beaver dam numbers peak during low base flows. Beaver ponds were surveyed in 2015 and 2018. Turn-over rates of dams was high, based on new dams constructed annually (𝑥̅=70.7±26.0(STD)%). Number of dams increased quadratically along the Middle Reach (pre-existing and new) from 8 in 2008 to 56 in 2018. Dam densities along the Middle Reach ranged from 0.5 to 5.2 dams/km. Overall, 63.5% of all beaver dams crossed the stream. Average length of a dam was 7.5±6.8(1 STD) m, ranging from 2.25 to 40.0 m and did not differ among reaches. Average height of a dam was 0.96±0.40(1 STD) m, ranging from 0.10 to 2.0 m and was similar among reaches. Ponds averaged 0.05±0.05(1 STD) acres and .13±0.19(1 STD) acres and in 2015 and 2018, respectively, with 9.3% overlap. Location of eaver dam complexes shifted over time. Beaver dams concentrated in the Lower Reach in 2009. The Middle Reach was consistently occupied from 2013 through 2018 and the lower part of the Upper reach in 2015, 2017, and 2018. Sections of the Middle Reach where beaver dams and ponds became established changed from single-thread stream (12% functional) to a sinuous streambed (45-67% functional) between 2007 and 2018. In 2018, there was limited in-channel features and vegetation recovery, and the channel likely reconnected to groundwater and hyporheic zones. Vegetation and floodplain- and hyporheic connectivity may afford moderate flood and drought resilience; furthermore, water clarity and stream temperature amelioration continued to improve. Absence of beavers in the Upper Reach and continued livestock grazing impaired streambed and woody riparian recovery, effectively stalling improvement of the Upper Reach, where the streambed remains a single-thread stream (12% functional). The Lower Reach remained in stasis (12% functional), as beavers did no successfully colonize this reach, because food remained limited for beavers, spring flows removed beaver dams, and beavers were likely highly susceptible to predation in this narrow, incised stream. In the absence of beaver dams and other structures, such as log jams, there is little opportunity for the retention of sediments, aggradation of the stream bed, and recovery from a single-thread to a multi-thread, or sinuous stream bed
... The stream lengths affected by beavers overlap many other taxa, so beaver expansion may affect the population dynamics of salmonids (Oncorhynchus and Salvelinus; Rosenfeld et al. 2002, Burnett et al. 2007, amphibians (Stevens et al. 2007, Hossack et al. 2015, birds (Nummi and Holopainen 2014), and other species (Wright et al. 2002, Wright 2009). The longterm consequences of stream modification by beavers on other taxa will be a function of what stream and riparian conditions are changed (Collen and Gibson 2000), the magnitude of those changes (Kemp et al. 2012, Weber et al. 2017, Majerova et al. 2019, the portion of the river modified (Remillard et al 1987, Demmer and Beschta 2008, Macfarlane et al. 2017, and the durability of the constructed dams (Demmer andBeschta 2008, Andersen andShafroth 2010). ...
... To understand the magnitude of changes brought about by beavers, it is necessary to understand how often new dams are constructed and how they affect a variety of stream and riparian conditions at a regional scale. Previous studies have demonstrated that beavers alter important aquatic and riparian attributes such as physical stream conditions (Beier and Barrett 1987, Collen and Gibson 2000, Pollock et al. 2007), macroinvertebrate taxa (Clifford et al. 1993, Washko et al. 2020, stream temperatures (Law et al. 2014, Majerova et al. 2015, Weber et al. 2017, and the vegetative community (Wright et al. 2002, Little et al. 2012. Few field studies have concurrently evaluated stream conditions, macroinvertebrates, water temperature, and the riparian community across a broadly dispersed sample of beaver-affected stream reaches. ...
... Comparisons of the stream, macroinvertebrate, temperature, and riparian metrics were significantly different between beaver-dammed and control reaches for 13 of the 18 metrics (Table 2). Generally, the presence of beaver dams was associated with deeper pools, finer sediments, warmer stream temperatures, and vegetation associated with higher water tables (Collen and Gibson 2000). Differences in the macroinvertebrate community metrics were more difficult to interpret because the indicator of stream health was higher in beaverimpacted stream reaches, but the number of pollution-intolerant species was higher in the control reaches. ...
Article
Full-text available
A before-after control-impact (BACI) design was used to simultaneously evaluate how stream habitat, macroinvertebrate communities, stream temperatures, and riparian conditions responded to beavers building damswithin a stream reach. Summarized conditions describing beaver-dammed and undammed stream reaches suggested that 13 of the 18 evaluated metrics differed. After accounting for beavers’ selection of lower-gradient stream reaches with less forested cover, the number of stream and riparian metrics that differed significantly dropped to 5. Beaver dams increased pool area and depth, despite failing to increase the frequency of wood >10 cm in diameter. This suggests that beavers build dams utilizing pieces of wood smaller than most monitoring programs count. Changes in stream and riparian conditions due to beavers were insufficient to alter macroinvertebrate metrics commonly used to assess water quality. The presence of beaver dams in a reach was associated with less vegetative and woody cover along the stream’s edge. The reduction of shrub cover and the presence of upstream beaver dams likely played a role in the small increases observed in water temperatures. The fact that beavers tended to build dams in reaches with elevated water tables may have minimized water temperature increases. Based on the beaver occupancy rate found in this study, changes in stream and riparian conditions due to new beaver dams should be expected in 5% to 15% of the stream reaches similar to those in this study over the next 2 decades. An increasing number of beavers occupying stream reaches represents animportant passive restoration approach that will improve the quality of aquatic systems on public lands.
... Trapping led to the extirpation of beavers from the Southern Appalachians at the end of the 19th century (McGrath, Olfenbuttel & Summer, 2018); however, beavers were reintroduced to the area in the mid-20th century and are now experiencing a resurgence (McGrath, Olfenbuttel & Summer, 2018). North American beavers are ecosystem engineers, and their activities may substantially alter ecosystems through non-trophic effects (Jones, Lawton & Shachak, 1994;Schlosser & Kallemeyn, 2000;Collen & Gibson, 2001). Beaver dams form temporary lentic habitats within stream networks, although these habitats can persist for decades (Snodgrass & Meffe, 1998;Collen & Gibson, 2001). ...
... North American beavers are ecosystem engineers, and their activities may substantially alter ecosystems through non-trophic effects (Jones, Lawton & Shachak, 1994;Schlosser & Kallemeyn, 2000;Collen & Gibson, 2001). Beaver dams form temporary lentic habitats within stream networks, although these habitats can persist for decades (Snodgrass & Meffe, 1998;Collen & Gibson, 2001). Such lentic habitats are rare in the Southern Appalachians, with Mountain Lake in Virginia representing the only natural lake of significance in the region (Cawley, Parker & Perren, 2001). ...
... As beavers return to the habitats they once occupied, both in the Southern Appalachians and other parts of the world, questions have begun to arise about how they will affect fish communities in streams where they construct ponds. Beaver ponds are known to have a wide range of effects on freshwater fish diversity and community structure, but the magnitude and direction of these effects is highly dependent on the spatial, temporal, and biogeographical context (Snodgrass & Meffe, 1998;Schlosser & Kallemeyn, 2000;Collen & Gibson, 2001;Kemp et al., 2011;Smith & Mather, 2013). The age and size of a beaver pond, together with the position of the pond within a stream network or the time of year that sampling is conducted have all been shown to affect the response of fishes to beaver activity (Snodgrass & Meffe, 1998;Schlosser & Kallemeyn, 2000). ...
Article
North American beavers (Castor canadensis) are ecosystem engineers that create novel habitats in stream ecosystems. Although driven to the edge of extinction by historical over‐exploitation, beavers are recolonizing much of their former range. In the Southern Appalachian Mountains beavers alter habitats occupied by diverse fish communities across a mosaic of changing forest cover and management priorities. Fishes were sampled from nine streams with active beaver ponds and from seven streams with inactive ponds in the Southern Appalachians during summer 2019. The status of beaver ponds was among the most important factors affecting fish communities; however, both active and inactive beaver ponds affected fish community structure, α‐diversity, and local contributions to β‐diversity (LCBD). Fish α‐diversity was lower in reaches from streams with active ponds and the magnitude of this reduction was dependent on the position relative to a pond. However, both active and abandoned beaver ponds and pond tail races had higher LCBD values compared with free‐flowing reaches. Arcsin‐transformed forest cover did not improve the model fit for any dependent variables. Indicator species analysis found that two species had an association with active beaver ponds, whereas eight species were associated with inactive beaver ponds or free‐flowing reaches. The effects of beaver impoundments on fish communities in Appalachian streams are dependent on the pond activity level and spatial context. Although diversity and species richness may be reduced in individual habitats, beaver ponds contribute to higher biodiversity at a regional spatial scale. An increased understanding of beaver effects on Southern Appalachian fish communities will enable stakeholders to make informed decisions regarding the management of sensitive or economically important fishes. Mitigating conflicts between sensitive resources and these ecosystem engineers will become an increasingly important management concern as beaver populations recover in the Southern Appalachians.
... Thus, throughout much of the northern hemisphere, beaver have been creating structurally complex and biologically diverse aquatic habitat for millions of years, and many anadromous and freshwater fishes have adapted to and evolved in such habitat [26,27]. In addition to dams, beaver create complex habitat through the construction of lodges and caches made of wood from nearby trees that they fell, as well as the excavation of soil to build canals, channels, tunnels and burrows [5]. ...
... clarkii) and brook trout (Salvelinus fontinalus) [6]. Many fishes use the structurally complex, deep, slow water and emergent wetlands created upstream of beaver dams [26,28]. Beaver build dams typically ranging from 30-100 cm, but may be as high as 250 cm, and the height of such dams has raised concerns that they are barriers to fish passage, particularly for salmon and trout [28,29]. ...
... different life-history stages and under all flow conditions. Upon review we found that most studies concluded that fishes, and in particular salmonids, benefit from natural obstructions such as beaver dams [6,26,38], while studies arguing that beaver dams are detrimental to fish are uncommon, and typically indicate a temporally intermittent negative impact, with no indication of a population-level effect [28]. For example, over a period of 12 years in Nova Scotia, it was observed that in years with low flow, adult Atlantic salmon were unable to pass over some beaver dams and thus spawned lower in the system, but in most years, beaver dams had no detectable effect on the distribution of spawning redds [57]. ...
Article
Full-text available
Across Eurasia and North America, beaver ( Castor spp), their dams and their human-built analogues are becoming increasingly common restoration tools to facilitate recovery of streams and wetlands, providing a natural and cost-effective means of restoring dynamic fluvial ecosystems. Although the use of beaver ponds by numerous fish and wildlife species is well documented, debate continues as to the benefits of beaver dams, primarily because dams are perceived as barriers to fish movement, particularly migratory species such as salmonids. In this study, through a series of field experiments, we tested the ability of juvenile salmonids to cross constructed beaver dams (aka beaver dam analogues). Two species, coho salmon ( Oncorhynchus kisutch ) and steelhead trout ( O . mykiss ), were tracked using passive integrated transponder tags (PIT tags) as they crossed constructed beaver dam analogues. We found that when we tagged and moved these fishes from immediately upstream of the dams to immediately downstream of them, most were detected upstream within 36 hours of displacement. By the end of a 21-day field experiment, 91% of the displaced juvenile coho and 54% of the juvenile steelhead trout were detected on antennas upstream of the dams. In contrast, during the final week of the 21-day experiment, just 1 of 158 coho salmon and 6 of 40 (15%) of the steelhead trout were still detected on antennas in the release pool below the dams. A similar but shorter 4-day pilot experiment with only steelhead trout produced similar results. In contrast, in a non-displacement experiment, juveniles of both species that were captured, tagged and released in a pool 50 m below the dams showed little inclination to move upstream. Further, by measuring hydraulic conditions at the major flowpaths over and around the dams, we provide insight into low-flow conditions under which juvenile salmonids are able to cross these constructed beaver dams, and that multiple types of flowpaths may be beneficial towards assisting fish movement past instream restoration structures. Finally, we compared estimates of the number of juvenile salmonids using the pond habitat upstream of the dam relative to the number that the dam may have prevented from moving upstream. Upstream of the dams we found an abundance of juvenile salmonids and a several orders of magnitude difference in favor of the number of juveniles using the pond habitat upstream of the dam. In sum, our study suggests beaver dams, BDAs, and other channel spanning habitat features should be preserved and restored rather than removed as perceived obstructions to fish passage.
... Evaluating the expected benefits of BRR is challenging because it is often implemented without formal study (Pilliod et al., 2017). When BRR efforts are evaluated, reports are highly variable across watersheds (Collen & Gibson, 2000) or through time (Clark, 2020) particularly with regard to stream temperature. A meta-analysis of studies considering the effect of beaver ponds on stream temperature indicated that downstream warming was the most common response (Ecke et al., 2017). ...
... Overall, our temperature findings add to syntheses of previous studies that reported warming stream temperatures below beaver dams (Collen & Gibson, 2000;Ecke et al., 2017;Johnson-Bice et al., 2018). ...
... Without reference data, we cannot definitively attribute the hypoxic DO conditions that we observed in the two ponds as unique to the respective upstream reaches. Our observations, however, are consistent with expectations that respiration would deplete DO in isolated lentic environments such as aquaculture ponds (Chang & Ouyang, 1988;Romaire et al., 1978) and described in reviews (Collen & Gibson, 2000) and meta-analysis (Ecke et al., 2017) of beaver pond influences on streams. Hypoxic conditions in the two beaver ponds we observed appear much more limiting to salmonids than the thermal impacts discussed above. ...
Article
Beaver‐related restoration (BRR) has gained popularity as a means of improving stream ecosystems, but the effects are not fully understood. Studies of dissolved oxygen (DO) and water temperature, key water quality metrics for salmonids, have demonstrated improved conditions in some cases, but warming and decreased DO have been more commonly reported in meta‐analyses. These results point to the contingencies that can influence outcomes from BRR. We examined water quality related to beaver ponds in a diverse coastal watershed (Umpqua River Basin, OR, USA). We monitored water temperature 0‐400 m above and below beaver ponds and at pond surfaces and bottoms across seven study sites from June through September of 2019. DO was also recorded at two sites at pond surfaces and pond bottoms. Downstream monthly mean daily maximum temperatures were warmer than upstream reference locations by up to 1.9 oC at beaver dam outlets but this heating signal attenuated with downstream distance. Downstream warming was greatest in June and July and best predicted by pond bottom temperatures. DO at pond surfaces and bottoms were hypoxic (≤ 5 mg/L) for more than half of the 32 d monitoring period. Water temperatures increased for short distances below monitored beaver ponds and observed oxygen conditions within ponds were largely unsuitable for salmonid fishes. These findings contrast with expectations of BRR and we recommend that managers consider expectations prior to implementation. In some cases, project goals may override water quality concerns but in streams where temperature or DO restoration are objectives, managers may consider using BRR techniques with caution.
... The North American beaver (Castor canadensis) is an herbivorous, semi-aquatic mammal that can significantly alter riparian landscapes by impounding water, flooding surrounding uplands, felling trees, and burrowing (Collen and Gibson 2001). Beavers conflict with humans when their activities flood roadways, agricultural fields, and damage timber resources (Taylor et al. 2017, Tremblay et al. 2017). ...
... Beavers conflict with humans when their activities flood roadways, agricultural fields, and damage timber resources (Taylor et al. 2017, Tremblay et al. 2017). In the upper Midwest, beaver impoundments may negatively impact cold water ecosystems by causing siltation of trout spawning habitat, warming water temperatures, and creating barriers to fish migration (Collen andGibson 2001, Avery 2002). The United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (USDA-WS), in partnership with the Wisconsin Department of Natural Resources (WDNR) and other local governments, manage beavers in Wisconsin to protect cold water ecosystems, roadways, wild rice lakes, wildlife impoundments, and railroads. ...
... The United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (USDA-WS), in partnership with the Wisconsin Department of Natural Resources (WDNR) and other local governments, manage beavers in Wisconsin to protect cold water ecosystems, roadways, wild rice lakes, wildlife impoundments, and railroads. Trapping is an effective management tool used for beaver management (Collen and Gibson 2001, Ruid 2003, Ribic et al. 2017. The size 330 body-grip trap, a rotating-jaw animal trap, is the most commonly-used trap by licensed beaver trappers (Responsive Management 2015). ...
Article
Full-text available
River otter (Lontra canadensis) populations in North America have been the focus of significant restoration efforts. Wildlife management agencies, concerned about the unintentional take of river otters incidental to beaver (Castor canadensis) trapping, may recommend techniques to avoid capturing river otters. River otter avoidance techniques that are ineffective or diminish trap performance for beavers are undesirable. We conducted a field evaluation in 2015 and 2016 in Wisconsin to assess how two trigger configurations (offset and center) on body‐grip traps would affect the incidental capture rate of river otters during beaver trapping. We also evaluated effects of each configuration on beaver capture rates, body lengths, and anatomical locations of trap‐jaw strikes. We used size 330 body‐grip traps equipped with identical triggers and alternated between trigger configurations during beaver damage management activities. We captured 8 river otters with each trap trigger configuration. Trap‐jaw strikes on beavers differed between trigger configurations, with offset triggers resulting in more abdomen strikes and center triggers causing more cervical vertebrae strikes. We found that an offset trigger configuration did not reduce incidental take of otters and was less effective for trapping beavers. © 2021 The Wildlife Society. This article has been contributed to by US Government employees and their work is in the public domain in the USA. An offset trigger configuration on 330 sized body‐grip traps does not reduce incidental river otter captures and makes traps less effective for capturing beaver. Wildlife agencies should consider other beaver trapping techniques to avoid incidental take of river otter.
... Examples of ecosystem engineers have been described for marine (Wang et al., 2010) and freshwater ecosystems (Zanetell and Peckarsky, 1996) and various wetlands (Collen and Gibson, 2001). American alligators (Alligator mississipiensis) attain large body sizes and increase spatial diversity in the Everglades swamps (Palmer and Mazzotti, 2004) whereas small animals such as sand-burrowing crabs mix sediment (Wang et al., 2010). ...
... Dynamic dam and pond cascades develop between running stream fragments (Bylak et al., 2014). Dams limit stream deposit transport and ponds are filled with material inputs (Collen and Gibson, 2001;Baker and Hill, 2003). Organic matter transported from the catchment accumulates in the stream. ...
... In contrast, relatively high temperatures may lower the pond's value as a habitat for stenotopic mountain stream organisms. Slowed water flow above a beaver dam, particularly water covering a stony bottom with fine-particle sediment, causes the disappearance of many taxa of benthic invertebrates that are typical of mountain streams, such as rheophilic stoneflies (Plecoptera), mayflies (Ephemeroptera), and caddisflies (Trichoptera) (Collen and Gibson, 2001). Bottoms covered with minerals and organic sediments are inhabited by numerous larvae of chironomids (Chironomidae) and oligochaetes (Oligochaeta). ...
Article
Elucidating the impact of faunal activity on stream channels is an emerging field wherein ecologists, fluvial geomorphologists, and engineers collaborate to research and manage fluvial ecosystems. Here, we focused on the geomorphological effects of animals in mountain streams. This ecosystem merits conservation measures as it furnishes cold-water refugia. We searched literature addressing the impact of various animal taxa on the river/stream bed structure. The citation sources were the Web of Science, Scopus, and ScienceDirect databases covering 1975–early 2020. We examined all animal taxa with documented or potential zoogeomorphological effects upon streams and assigned spatiotemporal scales to their impacts. Interpreting the literature was challenging due to a lack of uniformity in data treatment between species groups and over time. Though human interactions prevail in stream channels, animals also have a substantial effect on a spatial scale and their modifications are more durable. In general, animals markedly influence aquatic habitats. This literature compilation revealed much information about the geomorphological effects of beavers, redd-building fish, and large bottom-dwelling fish. The scale of impact of invertebrates such as crayfish or case-building caddisfly larvae on stony-gravel bottoms has previously been demonstrated. However, previous research has concentrated on only one taxon and has not demonstrated the bioaccumulation effect of multiple taxa. Quantitative data have been presented only for large terrestrial mammals crossing streams. There was comparatively little information on the impact of other terrestrial taxa on stream geomorphology. There were also few or no quantitative data on the impacts of aquatic fauna on mountain stream channels. Much has been reported about the effects of burying invertebrates but relatively little is known about the impacts of burying fish such as lamprey larvae. The present review highlights numerous outstanding information gaps. It is hoped that this review will facilitate ongoing zoogeomorphological research.
... There is also some debate surrounding increases in average stream temperature and how this increase might adversely affect in-stream habitat (Collen and Gibson, 2000). This review revealed that, overall, these effects are very local. ...
... However, it was beyond the scope of this study to evaluate the effects on in-stream ecology directly. Examples that address those relationships include reviews by Collen and Gibson (2000) and Kemp et al. (2012). Gaywood et al. (2015) provide a comprehensive review of the effects of beaver activity on ecology in Scotland. ...
... fiber). Despite strong genetic differences between the 2 species, they are similar enough morphologically and functionally that inference regarding either species is considered interchangeable (Macdonald et al. 1995, Collen andGibson 2001). ...
... Beavers are one of the few animals that manipulate their environment to change aspects of local habitat (Naimen et al. 1986). Beavers act as ecological engineers by building dams and creating ponds, which creates habitat that increases biodiversity of plants (Law et al. 2017), amphibians (Stevens et al. 2007), fish (Collen and Gibson 2001), waterfowl (Nummi et al. 2019), and insects (Mourant et al. 2018). The historical range of beaver extended across most of the northern hemisphere (Novak 1987, Macdonald et al. 1995. ...
Article
Understanding spatial and temporal variation in beaver abundance is a central goal for a wide range of management issues, ranging from species reintroductions to mitigation of environmental and economic impacts. Yet due to high costs associated with surveys, many studies are limited to a single regional estimate, or a complete census of a smaller study area extrapolated to the surrounding landscape. We present a survey design that allows for predicting beaver abundance across the broader landscape through interpolation. In October 2019, we conducted an aerial survey in a 15,000 km2 study area around Algonquin Provincial Park in Ontario, Canada. We counted 145 colonies on 73 plots that averaged 4.5 km2 (+/−3.27 SD). Our regional estimate for beaver abundance of 0.55 (95% CI = +/−0.18) colonies/km2 is comparable to historical surveys conducted in the region in the 1970s. We then predicted beaver abundance in unsampled plots using a Poisson generalized additive model (adjusted R2 = 0.81, deviance explained = 55.9%) that included non‐linear responses to elevation (P < 0.001), shoreline complexity (P = 0.003), and availability of shade‐tolerant hardwoods (P = 0.001). Our species distribution model predicted strong east‐west patterns in beaver abundance across the study region associated with spatial patterns in elevation and forest composition. Our study demonstrates that plot‐based survey designs can be an effective method for estimating spatial patterns of beaver abundance. We found elevation, shoreline complexity, and availability of shade‐tolerant hardwoods to be the most important predictors of beaver abundance around Algonquin Provincial Park, Ontario, Canada.
... The reduction in average daily maximum stream temperature fell in the lower range of cooling effects predicted for a stream in eastern Oregon upon restoration of the natural vegetation (-2.4 to -7.8 °C; Wondzell et al. 2019). The presence of beaver dams and ponds may also cause an amelioration of surface water temperature (Collen and Gibson 2001). Absent of any significant streamside shading, Weber et al. (2017) attributed an observed moderation in summer diurnal temperature cycles of -2.6 °C downstream of beaver complexes to beaver induced changes in hydrogeomorphic processes, in particular increased surface water storage and enhanced hyporheic exchange in beaver ponds. ...
... Beaver colonization further upstream into the upper reach was possibly constrained by a lack of sufficient forage, such as cottonwoods and willows, and an increased risk of predation in the wider, more shallow streambed of this part of Daly Creek (Collen and Gibson 2001). In the lower reach, beavers were unable to establish a permanent presence. ...
Article
Abstract In this study I document the results of 11 years of passive restoration of a small mountain stream in northeastern Oregon. Removal of the main stressors on the system, grazing and agricultural practices, resulted in a strong recovery of the riparian vegetation over the middle two thirds of the reach. Cover of trees and shrubs tripled, tree density increased 7-fold and stream shading 4-fold over the period 2007–2018. Average maximum daily stream temperature declined by 2.1–2.8 oC and average maximum diurnal temperature range narrowed by 3.7–4.6 oC. Recolonizing American beavers (Castor canadensis) played an essential role in improving the condition of the streambed over 18% of the reach. Their dams and ponds initiated the process of streambed aggradation and transformed the single-thread, incised channel into a multi-thread configuration within beaver complexes. Vegetation expansion was much stronger in impounded- than in un-impounded parts of the stream. Passive restoration was not effective in two sections together comprising one third of the reach. In the upper part of the stream recovery stalled because of continued (unauthorized) trespass grazing during late summer and fall. The channelized lower section of the stream was too severely modified for measurable recovery to occur. Using a recently developed Stream Evolution Model I concluded that 11 years of passive restoration improved the condition of the stream from 24% to 32%, and within beaver complexes, up to 57%.
... The studies have concluded that the construction of dams by the mammals in river channels influences plant and animal communities (e.g., Collen & Gibson, 2001;Rosell et al., 2005). Long-term research on the ecological role of the Eurasian beaver in undisturbed environments is possible in largely inaccessible mountain landscapes or in protected areas, where the animals can transform their habitats without any human disturbance (Bylak et al., 2014. ...
... Dams are, however, built on many small streams (Collen & Gibson, 2001). ...
Article
Beavers are an exception among animals in terms of the scale of environmental transformations they achieve. This study investigated primary environmental factors influencing the occurrence of aquatic invertebrates in lowland streams inhabited by the Eurasian beaver. The study was conducted in two forest streams inhabited by beavers, and in an uninhabited stream. In streams inhabited by beavers, the study covered seven ponds. Sections with flowing water were also analysed downstream and upstream of the ponds. Benthos and water samples were collected at each site. Dissolved oxygen (DO) concentration and saturation were the only physicochemical parameters that indicated decreases in water quality in beaver ponds. The benthic communities of different beaver ponds were similar. The taxa that exerted the greatest influence on the similarity of the invertebrate fauna in the ponds were Oligochaeta and Chironomidae. Ostracods were also abundant in the ponds, whereas they were few in the flowing sections. Mayflies (Cloeon) and caddisflies belonging to the family Phryganeidae were also closely associated with the ponds. Caddisflies (Plectrocnemia and Sericostoma), mayflies (Baetis) and stoneflies (Nemourella and Leuctra) exhibited the highest correlation with DO concentrations, which is typical of flowing sections, and avoided stream fragments dammed by beavers. Bivalvia (Pisidium) were also abundant in each of the streams along the flowing sections. The highest number of taxa and greatest taxonomic diversity was observed in sections flowing below the beaver ponds. The engineering activity of beavers transformed the studied lowland streams, resulting in the development of rheophilic and stagnophilic communities of aquatic invertebrates, in freeflowing and dammed sections, respectively.
... Published information on small wood sizes in dams of Beaver is lacking. However, Beaver most often forage on trees ranging from 1.2 -3.2 in (3 -8 cm) in diameter (Collen and Gibson 2001), and a large proportion of woody stems used as food are also used in dam construction (Barnes and Mallik 1996). In Maryland, Blersch and Kangas (2014) found that 98% of sticks (i.e., small wood) in a Beaver dam were less than 4 in (10 cm) in diameter and that 46% of those sticks were probably placed in the dam by Beaver. ...
... However, Beaver most often forage on trees ranging from 1.2 to 3.2 in (3 to 8 cm) in diameter (Collen and Gibson 2001), and a large proportion of woody stems used as food are also used in dam construction (Barnes and Mallik 1996). In Maryland, Blersch and Kangas (2014) found that 98% of sticks (i.e., small wood) in a Beaver dam were less than 4 in (10 cm) in diameter and According to Besides research on marine derived nutrients , the dynamics of macronutrients-nitrogen, phosphorus, and carbon (N, P, and C)-in riparian areas of the Pacific Northwest has been largely neglected by scientists (but see Naiman and Sedell 1980;). ...
Technical Report
Full-text available
This report contains reviews and syntheses of scientific literature for the purpose of informing the development of policies related to management of riparian areas and watersheds of Washington State.
... Of course, beaver dam construction is highly variable and depends on the existing habitat, building material availability, and channel characteristics (Collen & Gibson, 2000;Woo & Waddington, 1990). Woo and Waddington (1990) identified multiple ways in which dam structure will influence flow pathways and that streamflow can overtop or funnel through gaps in the dams, leak from the bottom of the dams or seep through the entire structure. ...
... Beaver increase the heterogeneity of stream depth, flow velocity, and benthic habitats such as silty substrates, woody material (Clifford, Wiley, & Casey, 1993;France, 1997;Rolauffs, Hering, & Lohse, 2001), and both submerged and emergent vegetation, which separately support unique invertebrate species and assemblages (Benke, Ward, & Richardson, 1999;Bush & Wissinger, 2016;Law, Levanoni, et al., 2019;Wissinger & Gallagher, 1999). Beaver ponds support more lentic species (Collen & Gibson, 2000;Margolis et al., 2001;Rosell et al., 2005) and typically demonstrate increased invertebrate abundance (Czerniawski & Sługocki, 2018;Osipov, Bashinskiy, & Podshivalina, 2018;Strzelec, Białek, & Spyra, 2018;Willby et al., 2018), biomass (Osipov et al., 2018) and/or density (McDowell & Naiman, 1986). Beaver ponds may harbor unique assemblages, dominated by collector-gatherers, shredders, and/or predators (Law et al., 2016;McDowell & Naiman, 1986;Robinson, Schweizer, Larsen, Schubert, & Siebers, 2020;Strzelec et al., 2018). ...
Article
Full-text available
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 This article reviews the state‐of‐the‐art scientific understanding of the beaver as an ecosystem engineer. It 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.
... Water is a key resource and slight water level fluctuations can have substantial effects on the colony [36][37][38]. Beavers can adjust to changes in water level through excavation of entrances or by adding material to the lodge (branches or mud) [39]. In cold climates, beavers need a minimum water depth to dive under frozen ponds and feed on their food cache [40]. ...
... While beavers need to operate both under water and on land, they are much better swimmers than walkers and spend less energy when moving under water than on land [67]. Last, in cold environments when water bodies can freeze, beavers need to dive under the ice and feed from the food cache without having to leave the proximity of the lodge in winter [39]. Hence, a minimum water level ensures a quick and safe access to the lodge under ice. ...
Article
Full-text available
Research Highlights: Lodge abandonment by beavers is apparently a common phenomenon in Patagonia, but it is still poorly understood and we ignore what drives it. In relatively slow growth Nothofagus forests, resource depletion can impact abandonment while water availability may be a major driver in the semiarid steppe. Background and Objectives: North American beaver (Castor canadensis) was introduced in 1946 on the island of Tierra del Fuego (TDF) in southern Argentina. Since then, beavers have become a major disturbance affecting not only forest but also treeless steppe landscapes. Our goal was to determine the factors affecting lodge abandonment by beavers in two habitats of TDF: forest and steppe. Materials and Methods: A total of 47 lodges were surveyed between February and March from 2012 to 2014 in both habitat types, 22 in the forest and 25 in the steppe. To explain factors involved in lodge abandonment by beavers, we measured the following variables: water level variation, stream gradient, vegetation cover adjacent to shore and forest structure. Results: We recorded 24 abandonments events, with a similar proportion of lodges abandoned in both habitats. Our results revealed that lodge abandonment was mostly linked to water level fluctuations irrespective of habitat type. The water level at the entrances of the lodge generally decreased in abandoned lodges. Variables that characterize understory cover had some influence on lodge abandonment in the forest, and no effect in the steppe. Conclusions: Water level variation was associated with lodge abandonment in both habitats, and we found some evidence of resource depletion in the forest. However, we caution that changes in water level may be not only due to extrinsic factors but rather to beaver's own activities or to a decay in pond maintenance following abandonment.
... Lentic habitat can provide breeding habitats for a variety of stream species. For example, beaver ponds provide natural and potentially important habitat to some stream fishes (Schlosser 1995(Schlosser , 1998Snodgrass and Meffe 1999) and amphibians (Collen and Gibson 2000;Cunningham et al. 2007;Stevens et al. 2007). Further research is necessary to untangle the relative importance of stream-to-pond connectivity as well as abiotic filters in limiting farm pond communities. ...
Article
Dam construction affects freshwater ecosystems worldwide. While there is much focus on large impoundments, farm ponds are overlooked despite their near-ubiquity across human-altered landscapes. Within the Great Plains of North America, there are millions of farm ponds, yet little is known about the fish communities and factors structuring them. We propose a conceptual model where fish, amphibian, and crayfish abundances differ along a pond size and water permanency gradient and are further influenced by interactions among species. In the summer of 2021, we sampled 100 farm ponds across central Kansas, primarily on private land. Pond size and permanency explained community structure with smaller and less permanent ponds being dominated by amphibians and crayfish while larger ponds were dominated by stocked sportfish. Distribution modeling revealed a negative correlation between stocked fish and other community components indicating potential interactions. If we are to conserve headwater stream species, especially those that are threatened or endangered, strategies that integrate farm ponds seem necessary given their prevalence on the landscape.
... Reintroduction projects can unsettle social and ecological norms, are often controversial (Nyhus, 2016;Crowley et al., 2017), and can sometimes conflict with human interests as reintroduced wildlife disperses into new areas (Collen and Gibson, 2001;Schwab and Schmidbauer, 2003;Jonker et al., 2006;Jonker et al., 2006;Gaywood et al., 2008;Gaywood et al., 2015;Campbell-Palmer et al., 2016;Crowley et al., 2017). In order to integrate animals, such as the Eurasian beaver into the management of cultural landscapes and mitigate some of their undesirable impacts, it is recommended that the identification of conflicts with human interests should occur as soon as possible, and management techniques should be implemented before issues become more widespread (Campbell-Palmer et al., 2016). ...
Article
Full-text available
Introduction The Eurasian beaver ( Castor fiber ) is a native species to Britain that after being absent for 400 years has been restored to the English countryside. The first beavers were released into a reserve in Kent in 2001/02, making this one of the first beaver release areas in the UK. This paper examines attitudes towards beaver presence in the landscape as well as public perception of beaver benefits and impacts with respect to the environment and human society. Methods Qualitative questionnaires were utilised to investigate factors influencing social attitudes and support for beaver reintroduction, as well as the relationship between sociodemographic variables and attitudes. Inhabitants of Kent and its immediate surroundings were surveyed during June and July of 2020 (n=407) with a focus on three interest groups – environmentalists, farmers and the general public. Results Perceptions included mostly beneficial impacts on nature and biodiversity, whereas less positive impacts were associated with economics, agriculture and fisheries. In general, local attitudes towards beavers were positive, mainly sustained by feelings of liking this wildlife species and valuing their presence. People´s attitudes positively influence willingness to support the reintroduction of beavers. Twenty years after their initial release, results indicate broad support for the beaver reintroduction in Kent and people´s tolerance of beavers. The majority of respondents were in favour of nonintrusive management techniques to mitigate beavers’ undesirable impacts. Discussion These findings suggest the need to develop an optimal management strategy that incorporates public views and gives advice on the best approach to manage this wildlife species. This research provides theoretical and practical underpinning for beaver management and conservation in Britain.
... Beavers create dams, thereby increasing the retention of organic matter and sediments and altering local conditions for aquatic habitat [31]. Damming activities by beavers cause tree to fall, which creates open areas in riparian forests; this causes changes in species distribution and composition of trees [32]. Beaver activity limits migration of umbrella species, aquatic invertebrates and salmonid fish, reduces streams' self-cleaning capacity and degrades the overall ecosystem of a stream [33]. ...
Article
Full-text available
Riparian forests are important ecosystems located along the margins of freshwaters. Riparian zones provide many ecosystem services, such as nutrient modification, erosion and temperature control, leading to improvements in water quality in adjacent water ecosystems. In many areas, riparian forest management is restricted to improve adjacent water quality. The potential influence of forest management on water quality of small streams was assessed by analysing species composition and structural diversity in riparian forests. We collected data in riparian forests along 15 streams in the eastern Baltics (Latvia) with different water quality classes. We used detrended correspondence analysis and indicator species’ analysis to determine relationships between woody plants and understory vegetation. We also used ADONIS and ANOSIM analysis to determine possible factors that affect species composition. Our results suggested that water quality is affected by ground vegetation, which in turn was altered by stand density and total yield. Site-specific decision making in management is required in riparian forests to ensure the required conditions in the streams, because species composition differs between sites, dominant tree species and stand parameters (density, total yield, stand age). Introduction of Betula pubescens Ehrh. in coniferous stands is favourable to ensure litter fall quality and provide shade for streams during summer.
... Watersheds with impoundment structures delay streamflow concentration times compared to those without (Pollock et al., 2003) and exhibit a decrease in peak flow (Nyssen et al., 2011) as well as an overall reduction of suspended sediment export (Maret et al., 1987;Pollock et al., 2003;Stout et al., 2017). Impoundment structures are suggested to increase baseflows (Pollock et al., 2003) and may lead to increased, more stable summer low flows (Collen & Gibson, 2000;Stout et al., 2017). Overbank flooding of impounded water is also thought to be an important mechanism for groundwater recharge in riparian areas (Westbrook et al., 2006). ...
Article
Beavers are of increasing interest as a mechanism for ecosystem restoration. However, the physical watershed characteristics that allow for successful beaver re‐establishment are not consistent across habitat suitability models. We delineated the extent of beaver impounded surface water in the Pole Mountain Area (PMA) of Southeastern Wyoming with six National Agricultural Imagery Program acquisitions over an 18‐year time period via a random forest classification algorithm. We computed beaver pond area for first and second‐order watersheds within the PMA and related the impounded pond area to climatic metrics such as maximum annual snow water equivalent and snow melt and rain input into the ground. There was no apparent relationship between annual climate metrics and beaver pond area. Further, we developed a random forest regression model to correlate beaver pond area with topographically derived watershed characteristics (e.g., hillslope size, riparian area size) to explore physical controls on impounded area at the watershed scale. Controls differed for first and second‐order watersheds, with pond area in smaller watersheds largely being controlled by lateral water contributions from the hillslopes, and in the larger watersheds by water from upstream and available space in the riparian areas. Interestingly, vegetation height did not emerge as an important predictor for pond area, likely because of generally good availability of forage material in all watersheds. This study improves our understanding of watershed characteristics that contribute to beaver habitat suitability and can be used to guide beaver re‐introduction efforts through analysis targeted at identifying watersheds most appropriate to beaver pond construction.
... W literaturze wielokrotnie podsumowywano wpływ działalności bobrów na rozwój zbiorowisk roślinnych i dostępność siedlisk (np. Collen, Gibson 2001, Rosell i in. 2005, Janiszewski i in. ...
... Since then, they have vastly altered the ecosystem there (Anderson et al., 2009;Henn et al., 2016), caused the establishment of non-native plants (Martínez Pastur et al., 2006) and are beneficial for native but also non-native fish species (Malmierca et al., 2011). Beaver impacts include those on agriculture through flooding and erosion due to dam building and burrowing into flood banks, on forestry through tree damage, on fishery due to beaver dams being migration barriers and raising water temperatures, and on infrastructure due to dam failure (Butler and Malanson, 1994;Härkönen, 1999b;Collen and Gibson, 2000;Müller-Schwarze, 2011). To reduce such impacts, invasive North American beavers are now being hunted and trapped in both South America and Europe (Worth, 2014;Brommer et al., 2017). ...
Chapter
a.Aim Provides an overview of selected taxonomic groups of invasive freshwater species: plants, bivalves, crayfish, fish and mammals. b.Main concepts and main methods covered For invasive species in each taxonomic group, major introduction pathways are outlined as well as main impacts and management actions. c.Conclusions Invasive freshwater species can be found in a variety of taxonomic groups, only a few of which can be covered here. Many freshwater invaders are still expanding their ranges, and have large effects on biodiversity and socio-economics. Their ecology and impacts need to be more thoroughly investigated in order to improve their management.
... Beavers had a higher selection for diving at locations with clay sediment, which may be an important building material for lodges and dams [96], although dams are not present in our study site, and beavers may additionally make use of burrows dug into the riverbank whereby the clay sediment aids in enhancing the structural integrity of those burrows [157,158]. Lodges and dams are mostly repaired in the autumn [159,160], but may be repaired after flooding events too [161]. Mud is also widely used for beaver constructions [97], although mud substrates, Fig. 8 The predicted relationship ± 95% confidence interval between distance to beaver lodge and sediment type among dives within 150 m of the beaver lodge of nine individuals in a Eurasian beaver population in southeastern Norway. ...
Article
Full-text available
Background Semi-aquatic mammals exploit resources both on land and in water and may require both to meet their habitat requirements including food- and building resources, refuges, and for social interactions with conspecifics. Within this, the specific availability of both terrestrial and aquatic resources is expected to impact individual fitness. Beavers are highly dependent on water for movement and protection from predators. They are central place foragers and mostly forage on woody vegetation near water although aquatic vegetation may also be an important food resource. However, little is known about their use of aquatic habitats. We aimed to address this knowledge gap by dead-reckoning fine-scale movement tracks and classifying fine-scale diving events, which we then related to the spatial distribution of aquatic vegetation and habitat components within the territory. Results Overall, there was a statistically clear decrease in probability that diving would occur at dawn and with increasing distance from territory borders. In addition, the distance from the lodge at which animals dived decreased through the night and during the spring/early summer. There was strong selection for diving habitats located closer to the riverbank, with stronger selection for these areas being observed in individuals with larger home ranges. We saw a higher selection for diving above clay sediment, and within 150 m from the lodge, presumably because mud and clay sediment tended to be located closer to the lodge than sand and rock sediment. Furthermore, we found a clear selection for diving in the presence of quillwort ( Isoetes spp.), shoreweed ( Littorella uniflora ), and stonewort ( Nitella spp . ). Selection for these focal species was stronger among subordinate individuals. Individuals with lower body condition dived closer to the beaver lodge, and dives located further from the lodge were associated with high densities of aquatic vegetation. Conclusion We provide new knowledge on the aquatic habitat use in a semi-aquatic mammal and show how energetic constraints may shape how beavers spatially use the aquatic environment, whereby short and shallow dives appear most beneficial. We show how aquatic habitats may have great importance for both foraging, building materials and safety, and discuss to how they may affect the fitness of individuals.
... Further, a review of beaver activity impacts on fish populations by Collen and Gibson (2001) suggested more positive than negative impacts, but the size of the stream should be considered as well as the location of the beaver activity and size of the dams constructed. In small, narrow streams beaver activity can have a greater influence on habitat quality and fish communities as these streams get more easily dammed (Rosell et al., 2005). ...
Article
Full-text available
Atlantic salmon Salmo salar L. and brown trout Salmo trutta fario L. are species of high socio-economic and ecological value. Declining populations make them target species of fisheries management. This paper reviews the direct effects of deficient longitudinal connectivity, changes in discharge, high water temperatures, oxygen depletion, changes in water chemistry and increasing loads of fine sediment on the critical life stages of spawning, egg incubation and emergence. It further provides an overview about the basic autecological requirements of Atlantic salmon and brown trout and summarises important thresholds of physico-chemical tolerances. This collection of information provides important baselines for assessing historical, ongoing and new threats relevant for the management of both species in fresh waters. Critical early-life stages of both species are almost identical, creating synergies in conservation and restoration. Seaward-migrating forms are exposed to further stressors, but improving starting conditions can also greatly improve their resilience.
... Beavers were historically present in most North American streams but have been reintroduced and are naturally colonizing many streams after almost complete extirpation in the late 1800s [27]. Because of the important role they play in structuring riparian environments and regulating ecosystem processes [11,66], beavers are integral to healthy riparian systems, and it is important to understand and utilize their diverse effects in land management [67,68]. In addition to their positive effects on biodiversity, they have been credited with preserving critical habitats essential to threatened species. ...
Article
Full-text available
The North American beaver (Castor canadensis Kuhl) and cottonwoods (Populus spp.) are foundation species, the interactions of which define a much larger community and affect a threatened riparian habitat type. Few studies have tested the effect of these interactions on plant chemistry and a diverse arthropod community. We experimentally examined the impact of beaver foraging on riparian communities by first investigating beaver food preferences for one cottonwood species, Fremont cottonwood (P. fremontii S. Watson), compared to other locally available woody species. We next examined the impact of beaver foraging on twig chemistry and arthropod communities in paired samples of felled and unfelled cottonwood species in northern Arizona (P. fremontii) and southwestern Colorado (narrowleaf cottonwood, P. angustifolia James, and Eastern cottonwood, P. deltoides W. Bartram ex Marshall). Four major patterns emerged: (1) In a cafeteria experiment, beavers chose P. fremontii six times more often than other woody native and exotic species. (2) With two cottonwood species, we found that the nitrogen and salicortin concentrations were up to 45% greater and lignin concentration 14% lower in the juvenile resprout growth of felled trees than the juvenile growth on unfelled trees (six of seven analyses were significant for P. fremontii and four of six were significant for P. angustifolia). (3) With two cottonwood species, arthropod community composition on juvenile branches differed significantly between felled and unfelled trees, with up to 38% greater species richness, 114% greater relative abundance and 1282% greater species diversity on felled trees (six of seven analyses with P. fremontii and four of six analyses with P. angustifolia were significant). The above findings indicate that the highest arthropod diversity is achieved in the heterogenous stands of mixed felled and unfelled trees than in stands of cottonwoods, where beavers are not present. These results also indicate that beaver herbivory changes the chemical composition in 10 out of 13 chemical traits in the juvenile growth of two of the three cottonwood species to potentially allow better defense against future beaver herbivory. (4) With P. deltoides, only one of five analyses in chemistry was significant, and none of the four arthropod community analyses were significant, suggesting that this species and its arthropod community responds differently to beaver. Potential reasons for these differences are unknown. Overall, our findings suggest that in addition to their impact on riparian vegetation, other mammals, birds, and aquatic organisms, beavers also may define the arthropod communities of two of three foundation tree species in these riparian ecosystems.
... Many studies have focused on the effects of beavers on fishes; this applies to both the Canadian beaver Castor canadensis Kuhl, 1820 (Murphy et al. 1989;Schlosser 1995;Schlosser and Kallemeyn 2000;Collen and Gibson 2001;Mitchell and Cunjak 2007;Malison et al. 2016;Johnson-Bice et al. 2018;Wathen et al. 2019) and the Eurasian beaver (Hägglund and Sjoberg 1999;Zavyalov et al. 2005;Dgebuadze et al. 2001Dgebuadze et al. , 2007Kukuła and Bylak 2010;Dgebuadze and Zavyalov 2011;Leshchenko et al. 2013;Bylak et al. 2014;Virbickas et al. 2015;Popkov et al. 2018;Malison and Halley 2020). Beaver activity leads to the replacement of typical habitats in small rivers (riffles and raceways) with "beaver ponds." ...
Article
Full-text available
In recent decades, the Eurasian beaver (Castor fiber) has once again become the keystone species in small river ecosystems in Russia. In many places, beaver activity has resulted in a significant change in lotic habitats, affecting the diversity, density, and biomass of aquatic organisms, including fish. While many studies have considered the ecosystem impacts of beavers, relatively few have focused on understanding the influence of beaver activity on steppe rivers. We conducted the first quantitative study of beaver impacts on fish assemblages in beaver-influenced and beaver-free sites on two small steppe rivers in the Don River basin in Russia. The presence of beavers altered the habitats in small steppe rivers and affected the diversity, density, and biomass of fish. A comparison of the number of species, density, and biomass of fish in six types of river habitats showed that these parameters were lower in beaver ponds than at riverine sites without beaver activity. Three fish species primarily preferred a single habitat type. Barbatula barbatula was found in riffles, Misgurnus fossilis in old beaver ponds, and Eudontomyzon mariae in abandoned beaver ponds. Beavers impacted fish distribution and density by changing dissolved oxygen, pH, and water current velocity. Overall, our results showed that the presence of beavers led to a temporary homogenization of fish habitats at a local scale in the valleys of small steppe rivers because beavers occupied these rivers only for a short period. However, habitat heterogeneity may increase if the beaver population stays stable or expands in the future.
... Will the recovery of systems be adequate to sustain viable beaver populations? Will productivity approach historical levels of productivity that can sustain beaver and many wetland-dependent species and fishes (Collen and Gibson, 2001;Hossack et al., 2015;Law et al., 2016)? What timeframe is required for their sustainability? ...
Article
Extirpation of wolves from the Greater Yellowstone Ecosystem in the 1920s hypothetically triggered a trophic cascade in which herbivores over-browsed riparian zones once released from the fear of wolf (Canis lupus) predation. Eventually, vast meadow-wetland complexes transitioned to grass-lodgepole systems. By 1954, beaver (Castor canadensis) virtually abandoned the Greater Yellowstone Ecosystem. In 2000, Colorado State University established experimental dams with browsing exclosures for Long Term Environmental Research in Biology (LTREB) on three streams in Lamar Valley to compare hydrologic effects of pseudo-beaver dams and browsing on willow (Salix spp.) productivity and state transitions. In 2015, beaver began recolonizing the region. I investigate how the biogeochemical role of beaver versus their hydrologic influence affects the underlying mechanisms of state transition: nutrient cycling, productivity, and stream respiration. Analyses of the 2017 field samples showed that beaver streams trend toward higher nutrient levels and higher variances than the LTREB sites. These trends continued in 2018 and 2019. The data tentatively support the role of beaver as keystone species in state transitions. Interannual modeling of nutrient dynamics, comparisons of stream metabolism, and genetic identification of microbial communities are underway. Similarly, analyses of the repeated measures collected across the month of July 2019 are underway. Featured photo from figure 1 in report.
... Habitat alterations catalyzed by beaver dams can change local hydrology and increase habitat heterogeneity that correspondingly influences community composition and trophic structure (Wright et al. 2002;Anderson and Rosemond 2007;Smith and Mather 2013). Previous studies demonstrate effects on the diversity of zooplankton (Sferra et al. 2017), macroinvertebrates (Law et al. 2016;Bush et al. 2019), and macrophytes (Ray et al. 2001), and the attributes of fish assemblages (Collen and Gibson 2000). The differential response of fish community and trait composition to the successional stage-dependent environments of beaver ponds remains understudied; however, where earlier work has only compared fish community composition in streams to ponds (Smith and Mather 2013) or to very coarse successional stages (Snodgrass and Meffe 1998;Schlosser and Kallemeyn 2000). ...
Article
Full-text available
Metacommunity theory predicts that the relative importance of regional and local processes structuring communities will change over time since initiation of community assembly. Determining effects of these processes on species and trait diversity over succession remains largely unaddressed in metacommunity ecology to date, yet could confer an improved mechanistic understanding of community assembly. To test theoretical predictions of the increasing importance of local processes in structuring communities over successional stages in metacommunities, we evaluated fish species and trait diversity in three pond metacommunities undergoing secondary succession from beaver (Castor canadensis) disturbance. Processes influencing taxonomic and trait diversity were contrasted across pond communities of different ages and in reference streams. Counter to predictions, the local environment became less important in structuring communities over succession but did exert a stronger effect on trait sorting. Beta diversity and trait richness declined over succession while there was no influence on species richness or trait dispersion. The trait filtering in older habitats was likely a response to the larger and deeper pond ecosystems characteristic of late succession. In contrast to these observed effects in ponds, the local environment primarily structured species and trait diversity in streams. Analyses of the relative importance of regional and local processes in structuring fish assemblages within each pond metacommunity suggests that habitat age and connectivity were more important than the environment in structuring communities but contributions were region and scale-dependent. Together, these findings highlight that regional and local processes can differentially influence taxonomic and trait diversity in successional metacommunity mosaics.
... Despite the many documented ecological benefits of beaver activities, concerns remain regarding potential impacts of restored beaver populations on flooding of infrastructure and agricultural land, felling of commercial timber and ornamental trees (Campbell-Palmer et al. 2015), and the potential impacts on fish and fisheries, particularly those of economic importance such as salmonids (Kemp et al. 2012;Collen and Gibson 2000). By modifying riparian vegetation and providing in-stream structures, beaver dams can have both positive and negative effects on the production of stream dwelling salmonids (Kemp et al. 2012; Table 1). ...
Article
Full-text available
Globally, freshwaters are the most degraded and threatened of all ecosystems. In northern temperate regions, beaver reintroductions are increasingly used as a low-cost and self-sustaining means to restore river corridors. River modifications by beavers can increase availability of suitable habitat for fish, including salmonids. This study investigated the response of a population of brown trout to reintroduced beaver habitat modifications in northern Scotland. The field site comprised two streams entering a common loch; one modified by beavers, the other unaltered. Electrofishing and PIT telemetry surveys indicated abundance of post-young of the year (post-YOY) trout was higher in the modified stream. Considering juvenile year groups (YOY and post-YOY) combined, abundance and density varied with year and season. In the modified stream, fork length and mass were greater, there was a greater variety of age classes, and mean growth was positive during all seasons. Beavers had profound effects on the local brown trout population that promoted higher abundances of larger size classes. This study provides important insight into the possible future effect of beavers on freshwater ecosystems.
... Beavers require sufficient stream flow as a reliable water source. Yet, rivers should neither be too wide nor too deep to inhibit building and persistence of dams (Collen and Gibson, 2000;Gurnell, 1998;Macfarlane et al., 2017). ...
Article
Full-text available
Many geomorphic phenomena such as bank failures, landslide dams, riffle‐pool sequences and knickpoints can be modelled as spatial point processes. However, as the locations of these phenomena are constrained to lie on or alongside rivers, their analysis must account for the geometry and topology of river networks. Here, we introduce a new numeric class in TopoToolbox called Point Pattern on Stream networks (PPS), which supports exploratory analysis, statistical modelling, simulation and visualization of point processes. We present three case studies that aim at inferring processes and factors that control the spatial density of geomorphic phenomena along river networks: analysis of a synthetic dataset of points on a stream network, the analysis of knickpoints in river profiles, and modelling spatial locations of beaver dams based on topographic metrics. The case studies rely on exploratory analysis and statistical inference using inhomogeneous Poisson point processes. Thereby, statistical and probabilistic procedures implemented in PPS provide a systematic approach for treating and quantifying uncertainties. PPS provides a consistent numeric framework for modelling point processes on river networks with a wide range of applications in fluvial geomorphology, but also other disciplines such as ecology.
... A robin or an alligator that builds a nest is engaging in habitat construction, but the altered habitat persists for just a short period of time and affects (to first order) only the constructing individual and its immediate offspring. The construction of a beaver dam has more long-lasting effects as it can persist for several generations (Collen and Gibson 2000). The dam affects the physical environment by turning a stream into a pond that in turn affects vegetation in the pond's vicinity. ...
Article
Habitat construction and phenotypic plasticity are alternative responses to variable environments. We explored evolution along an environmental gradient of habitat construction alone and in combination with phenotypic plasticity using individual‐based simulations that manipulated the fitness benefit of construction and whether construction maintained or eliminated that gradient. Construction was favored when its benefits were more likely to flow to the immediate offspring of the constructing individuals. Habitat construction and phenotypic plasticity traded off against each other or plasticity was selected against, depending on how the optimum environment varied and with the fitness value of construction. When selection favored differences in the amount of construction along the environmental gradient, genetic differentiation for habitat construction increased as the fitness value of construction increased. The degree to which each adaptive response was likely to evolve also depended on the precise ordering of life history events. Adaptive habitat construction does not always occur and may be selected against. This article is protected by copyright. All rights reserved
... Beavers face their greatest predation risk on land because most of their predators are primarily terrestrial, and Beavers are more agile in water than on land (Basey and Jenkins 1995, Gable et al. 2018, McNew and Woolf 2005. Although in the southeastern US, Beavers have fewer terrestrial predators than in regions farther north, they may face some predation risk from Alligator mississippiensis (Daudin) (American Alligator) while in the water (Collen and Gibson 2001, McClintic et al. 2014, Wade and Ramsey 1986. Wildcat Brake appears to be just outside of the natural range of American Alligators (Powell et al. 2016), but the predators sometimes occur in the Yalobusha River drainage and have been seen there during the time span of our Beaver observation (L. ...
... T he North American beaver (Castor canadensis) is renowned as an ecosystem engineer with the ability to transform hydrologic, geomorphic, and ecological processes within stream ecosystems through the construction of dams (Naiman et al. 1988, Jones et al. 1994, Collen and Gibson 2001, Wright et al. 2002, Ecke et al. 2017. Historical reports describe near ubiquitous presence of beavers throughout North America prior to European settlement (Seton 1909, 1929, Jenkins and Busher 1979, but most populations were extirpated by the nineteenth century because of fur trapping and habitat conversion for agriculture (Hays 1871, Shaw and Fredine 1971, Johnston and Chance 1974. ...
Article
Full-text available
Beaver-related restoration is a process-based strategy that seeks to address wide-ranging ecological objectives by reestablishing dam building in degraded stream systems. Although the beaver-related restoration has broad appeal, especially in water-limited systems, its effectiveness is not yet well documented. In this article, we present a process-expectation framework that links beaver-related restoration tactics to commonly expected outcomes by identifying the set of process pathways that must occur to achieve those expected outcomes. We explore the contingency implicit within this framework using social and biophysical data from project and research sites. This analysis reveals that outcomes are often predicated on complex process pathways over which humans have limited control. Consequently, expectations often shift through the course of projects, suggesting that a more useful paradigm for evaluating process-based restoration would be to identify relevant processes and to rigorously document how projects do or do not proceed along expected process pathways using both quantitative and qualitative data.
... Its aquatic ecosystems are significantly modified as a result of the life activity of the European beaver (Castor fiber L., 1758) . Beaver dams stabilize the water level and lead to the accumulation of organic sediments in food webs (Collen and Gibson, 2000). During droughts, beaver ponds are used as refugia by aquatic inhabitants, including water beetles (Sazhnev and Zav'yalov, 2018). ...
Article
The content of mercury in adult water beetles is studied in beaver ponds located in the Polist-Lovat Swamp System (Novgorod oblast). A total of 201 individuals of nine species of the family Dytiscidae and one species of the family Hydrophilidae (size classes II and III) are studied. It is revealed that the mercury content in beetles of size class II differs significantly between species (χ2 = 32.93, p < 0.01). Maximum concentrations were found in Graphoderus cinereus (0.259 ± 0.091 μg/g dry weight), while minimum concentrations were recorded in Hydrochara caraboides (0.091 ± 0.020 μg/g dry weight). There were no significant differences in the mercury content between the III size class beetles (largest beetles) of the studied species. In beetles of size class II, the concentration of mercury decreases in the body with an increase in the body weight (Kendall rank coefficient τ = –0.31, p < 0.01). The mercury content in the body parts of beetles of the genus Dytiscus increases in order: the elytra and wings-legs-head and thorax-abdomen.
... We observed that the American beaver is extremely sensitive to human activities, perhaps because this species is completely confined to water bodies and riparian zones (Collen and Gibson 2000). In the process of landscape simulation, the change in the value of GYRATE_AM for habitats of this species indicated that its habitats may be severely influenced by human activities. ...
Article
Full-text available
Socioecological information should be properly employed in the process of spatial analysis, planning, and management in order to respond to complex and multidirectional biodiversity issues. We conducted this study to map socioecological hotspots, where landscapes of social significance and wildlife habitats overlap, show to what extent and how the spatial distribution of social values (SVs) of people toward their landscapes interact with wildlife habitats in socioecological hotspots, simulate the potential for habitat degradation as a result of human activities linked to SVs, identify strategic areas for landscape restoration in socioecological hotspots, where both environmental conditions and SVs support the persistence and colonization of wildlife, and detect specific areas, where SVs of people may be contradictive leading to land-use disputes. We developed a model to show the potential for habitat degradation based on the spatial distribution of SVs associated with landscapes. We restricted our study to the Upper Missouri River Basin (UMRB) and focused on habitats of five keystone mammal species to assess the validity of our model. Habitat loss, habitat subdivision, habitat dispersion, and habitat shrinkage can be four consequences of human activities for biodiversity in socioecological hotspots of the UMRB, however, the magnitude of impacts varies among landscapes and mammal species. Spatially explicit models to properly map SVs in relation to wildlife habitats are still associated with some uncertainties and limitations, and therefore, require further development. Change in SVs and public attitudes toward land use is essential to avoid further biodiversity loss in this region.
... Will the recovery of systems be adequate to sustain viable beaver populations? Will productivity approach historical levels of productivity that can sustain beaver and many wetland-dependent species and fishes (Collen and Gibson, 2000;Hossack et al., 2015;Law et al., 2016)? What timeframe is required for their sustainability? ...
Article
Extirpation of wolves from the Greater Yellowstone Ecosystem in the 1920s hypothetically triggered a trophic cascade in which browsers, released from wolf (Canis lupus) predation, over-browsed riparian zones. Eventually, vast meadow-wetland complexes transitioned to grass-lodgepole systems. By 1954, beaver (Castor canadensis) virtually abandoned the Greater Yellowstone Ecosystem. In 2000, Colorado State University established experimental dams with browsing exclosures for Long Term Environmental Research in Biology (LTREB) on three streams in Lamar Valley to compare hydrologic effects of pseudo-beaver dams and browsing on willow (Salix spp.) productivity and state transitions. In 2015, beaver began recolonizing the region. I investigated how the biogeochemical role of beaver versus their hydrologic influence affects the underlying mechanisms of state transition: nutrient cycling, productivity, and stream respiration. Analyses of the 2017 field samples show that beaver streams trend toward higher nutrient levels and higher variances than the LTREB sites. The data tentatively support the role of beaver as keystone species in state transitions, although more data are needed. The unexpected and late May notice from the NPS to obtain an independent research permit—approved late August—curtailed my 2018 research to a brief field bout in September. Analysis of 2018 samples is underway. Featured photo from Figure 1 in report.
... Beaver engineering is highly site specific and depends on the existing habitat, building material availability and channel characteristics (Collen & Gibson, 2000;Graham et al., 2020;Woo & Waddington, 1990). It is difficult to define a 'typical' dam, although Woo and Waddington (1990) identified some of the multiple ways in which dam structure can influence flow pathways i.e. stream flow can overtop or funnel through gaps in the dams, leak from the bottom of the dams or seep through the entire structure. ...
Article
Full-text available
Beavers can profoundly alter riparian environments, most conspicuously by creating dams and wetlands. Eurasian beaver (Castor fiber) populations are increasing and it has been suggested they could play a role in the provision of multiple ecosystem services, including natural flood management. Research at different scales, in contrasting ecosystems is required to establish to what extent beavers can impact on flood regimes. Therefore, this study determines whether flow regimes and flow responses to storm events were altered following the building of beaver dams and whether a flow attenuation effect could be significantly attributed to beaver activity. Four sites were monitored where beavers have been reintroduced in England. Continuous monitoring of hydrology, before and after beaver impacts, was undertaken on streams where beavers built sequences of dams. Stream orders ranged from 2nd to 4th, in both agricultural and forest-dominated catchments. Analysis of >1000 storm events, across four sites showed an overall trend of reduced total stormflow, increased peak rainfall to peak flow lag times and reduced peak flows, all suggesting flow attenuation, following beaver impacts. Additionally, reduced high flow to low flow ratios indicated that flow regimes were overall becoming less "flashy" following beaver reintroduction. Statistical analysis, showed the effect of beaver to be statistically significant in reducing peak flows with estimated overall reductions in peak flows from -0.359 to -0.065 m3 s-1 across sites. Analysis showed spatial and temporal variability in the hydrological response to beaver between sites, depending on the level of impact and seasonality. Critically, the effect of beavers in reducing peak flows persists for the largest storms monitored, showing that even in wet conditions, beaver dams can attenuate average flood flows by up to ca. 60%. This research indicates that beavers could play a role in delivering natural flood management.
... The ponds become silt traps and sometimes burst open to cause significant floods downstream (Rosell et al. 2005, Butler andMalanson 2005). The change in the habitat alters the composition of fish populations (Collen and Gibson 2001). Many species fish (e.g., salmon) dig nests on stream beds for laying their eggs. ...
... Beaver immigration presents an unprecedented opportunity in ecology to investigate several important questions about the interplay between the hydrologic and biologic mechanisms. From a conservation standpoint, will the recovery of systems be adequate to sustain viable beaver populations, and to establish historical levels of productivity that will sustain beaver and many wetland-dependent species and fishes (Collen and Gibson, 2000;Hossack et al., 2015;Law et al., 2016)? What timeframe is required for their sustainability? ...
Article
Extirpation of wolves from the Greater Yellowstone Ecosystem (GYE) in the 1920shypothetically triggered a behaviorally-mediated trophic cascade in which elk (Cervus elaphus), released from the fear of wolf (Canis lupus) predation, over-browsed riparian zones. Eventually, vast areas of meadow-wetland complexes transitioned to grass-lodgepole systems. The importance of beaver (Castor canadensis) in wetland losses has received less attention. Beaver abandoned most of the GYE by the 1950s, possibly due to resource limitations. Researchers from Colorado State University established an experimental system for Long Term Environmental Research in Biology (LTREB) along several streams in the Lamar Valley of Yellowstone sixteen years ago. To evaluate effects of hydrologic changes and elk browsing on productivity of willows (Salix spp.) and state transition, they built small experimental dams with browsing exclosures. In 2015, beaver began recolonizing the region. I am investigating how their biologic as well as hydrologic impacts affect the underlying mechanisms of state transition: nutrient cycling, productivity, and stream respiration. I posit that beaver are keystone species, meaning that the sustained recovery of wetland-meadow complexes is unlikely without the higher levels of riparian productivity triggered by the biological influence of beaver. Featured photo by Ben Amaral on Unsplash. https://unsplash.com/photos/rohY54N6auU
... downstream (Mitchell and Cunjak, 2007;Schlosser, 1995;Virbickas et al., 2015), or on adult mobility 1634 during low flow periods (Bylak et al., 2014;Collen and Gibson, 2000;Cunjak and Therrien, 1998;1635 Mitchell andCunjak, 2007;Schlosser, 1995;Taylor et al., 2010). In one study over 4 summers, large 1636 fractions of total upstream and downstream fish movement over dams occurred over only a 1 -2 day 1637 period that had slightly elevated streamflow, though not all days with elevated streamflow had 1638 increased mobility (Schlosser, 1995). ...
Preprint
Beavers (castor fiber, castor canadensis) are the most influential mammalian ecosystem engineer, heavily modifying river corridors and influencing hydrology, geomorphology, nutrient cycling, and ecosystems. As an agent of disturbance, they achieve this first and foremost through dam construction, which impounds flow and increases the extent of open water, and from which all other landscape and ecosystem impacts follow. After a long period of local and regional eradication, beaver populations have been recovering and expanding throughout Europe and North America, as well as an introduced species in South America, prompting a need to comprehensively review the current state of knowledge on how beavers influence the structure and function of river corridors. Here, we synthesize the overall impacts on hydrology, geomorphology, biogeochemistry, and aquatic and terrestrial ecosystems. Our key findings are that a complex of beaver dams can increase surface and subsurface water storage, modify the reach scale partitioning of water budgets, allow site specific flood attenuation, alter low flow hydrology, increase evaporation, increase water and nutrient residence times, increase geomorphic heterogeneity, delay sediment transport, increase carbon, nutrient and sediment storage, expand the extent of anaerobic conditions and interfaces, increase the downstream export of dissolved organic carbon and ammonium, decrease the downstream export of nitrate, increase lotic to lentic habitat transitions and aquatic primary production, induce ‘reverse’ succession in riparian vegetation assemblages, and increase habitat complexity and biodiversity on reach scales. We then examine the key feedbacks and overlaps between these changes caused by beavers, where the decrease in longitudinal hydrologic connectivity create ponds and wetlands, transitions between lentic to lotic ecosystems, increase vertical hydraulic exchange gradients, and biogeochemical cycling per unit stream length, while increased lateral connectivity will determine the extent of open water area and wetland and littoral zone habitats, and induce changed in aquatic and terrestrial ecosystem assemblages. However, the extent of these impacts depends firstly on the hydro-geomorphic landscape context, which determines the extent of floodplain inundation, a key driver of subsequent changes to hydrologic, geomorphic, biogeochemical, and ecosystem dynamics. Secondly, it depends on the length of time beavers can sustain disturbance at a given site, which is constrained by top down (e.g. predation) and bottom up (e.g. competition) feedbacks, and ultimately determines the pathways of river corridor landscape and ecosystem succession following beaver abandonment. This outsized influence of beavers on river corridor processes and feedbacks is also fundamentally distinct from what occurs in their absence. Current river management and restoration practices are therefore open to re-examination in order to account for the impacts of beavers, both positive and negative, such that they can potentially accommodate and enhance the ecosystem engineering services they provide. It is hoped that our synthesis and holistic framework for evaluating beaver impacts can be used in this endeavor by river scientists and managers into the future as beaver populations continue to expand in both numbers and range.
... The alteration of watercourses by beavers is well described in the literature, and reviews of various aspects of the species' influence on aquatic ecosystems have been published regularly (Naiman et al. 1988;Pollock et al. 1995;Gurnell 1997;Collen and Gibson 2000;Rosell et al. 2005;Gibson and Olden 2014;Janiszewski et al. 2014;Stringer and Gaywood 2016;Ecke et al. 2017). In most cases, attention is paid to changes caused by the building activities of beavers, which lead to transformation of lotic ecosystems into lentic ones. ...
Article
Full-text available
The aim of this review is to analyze the literature on the impact of beavers on lakes, summarize their effects, describe consequences for biotic and abiotic components, and highlight unresolved issues and perspectives. Beaver activity changes vegetation structure to the greatest extent, indirectly affecting other ecosystem components. Damming of flowing lakes increases the littoral area, which affects diversity and abundance of invertebrates, amphibians, birds, and mammals. Beavers’ alteration of the water regime and heterogeneity and connectivity of habitats has significant effects on zoobenthos, fish, and amphibians. Changes in hydrochemical properties directly affect phytoplankton and benthos. Unlike river ecosystems, where habitats are altered from flowing to still water, in lake ecosystems, habitat type is not usually changed (from lotic to lentic) but their quality (e.g., heterogeneity, connectivity) is. Beaver activity in rivers leads to increased limnophilic biodiversity, but in lakes, it leads to conservation of pre-existing lentic ecosystems. Therefore, impacts of beavers could be of greater importance to limnophilic complexes in lakes than to streams, especially after long time of beaver absence. Digging activity has a more significant role in lakes (especially floodplain) than in rivers. Beaver alteration of heterogeneity and connectivity of habitats is well studied, but not enough is known about impacts on the water regime of seasonally flowing waters, hydrochemical changes (especially eutrophication), amphibian life cycles, phytoplankton and zooplankton communities, parasitocenoses, and coarse woody debris. Methodological difficulties are noted, which are associated with the correct choice of control lakes. Further studies on riverine lakes are crucial. In considerations of climatic changes and anthropogenic impact, beavers may be an additional aid to conserving small lake ecosystems.
... Ее водные экосистемы значительно модифицированы в результате жизнедеятельности обыкновенного бобра (Castor fiber L., 1758) (Завьялов, 2015). Благодаря бобровым плотинам стабилизируется уровень воды, и накапливаются органические осадки, вовлекаемые в трофические сети (Collen, Gibson, 2000). В засуху пруды, созданные бобром, выступают в роли рефугиумов для водных обитателей, в том числе водных жесткокрылых (Сажнев, Завьялов, 2018). ...
Article
Mercury content in imago of water beetles is studied in beaver ponds situated in the Polist-Lovat Swamp System (Novgorod Oblast’, Russia). 201 individuals of 10 species of II and III size classes from families Dytiscidae and Hydrophilidae were observed. It was found that the mercury content in beetles of size class II significantly differs depending on the species (χ2 = 32.93, р < 0.01). The maximum concentrations were found in Graphoderus cinereus – 0.259 ± 0.091 μg/g of dry weight, the minimum concentrations in Hydrochara caraboides – 0.091 ± 0.020 μg/g of dry weight. There were no significant differences between the species of beetles of size class III. In beetles of size class II with increasing body weight the concentration of mercury in the body decreases (τ = –0.31, р < 0.01). It is shown that the mercury content in the body parts of the beetles of the genus Dytiscus increased in order: elytra and wings–legs–head, thorax and abdomen. Определено содержание ртути в имаго водных жуков, обитающих в бобровых прудах Полистово-Ловатской системы верховых болот (Новгородская обл.). Исследована 201 особь из девяти видов сем. Dytiscidae и одного вида сем. Hydrophilidae, относящихся к II и III размерным классам. Установлено, что в жуках II размерного класса содержание ртути достоверно различается между видами (χ2 = 32.93, р < 0.01). Максимальные концентрации выявлены у Graphoderus cinereus (0.259 ± 0.091 мкг/г сухой массы), минимальные – у Hydrochara caraboides (0.091± 0.020 мкг/г сухой массы). Для жуков III размерного класса (более крупных) достоверных различий в содержании ртути между видами не обнаружено. У жуков II размерного класса c увеличением массы тела уменьшается концентрация ртути в организме (ранговый коэффициент Кендалла τ = –0.31, р < 0.01). Содержание ртути в отделах тела жуков рода Dytiscus увеличивается в ряду: надкрылья и крылья–ноги–голова и грудь–брюшко.
... Incorporating GIS and remote sensing technologies, Johnston and Naiman (1990) somewhat successfully attempted to identify those habitats and examine the role of the beaver in an overall ecosystem. It is well documented that beaver have a dramatic impact on vegetation communities (Snodgrass, 1997), aquatic vertebrnte as well as invertebrate populations (Collen and Gibson, 2000;Olson and Hubert, 1994), and hydro-geomorphic processes (Meentemeyer and Butler, 1998;Gurnell, 1998). But, the dynamics of this influence is limited by lack of knowledge of the beaver population A comparison of changes over the past 25 years, since the work of Collins (1976), will offer insight into the population distribution. ...
Article
Our National Parks house some of North America's most undisturbed habitat and offer a benchmark for comparing ecosystem dynamics with areas more influenced by human related perturbations. Dam construction has altered water flow patterns on many of our country's rivers resulting in species composition changes of aquatic plants, invertebrates and fish. Semi-aquatic mammals such as otters and beaver are also profoundly influenced by the irregular seasonal flow patterns resulting from reservoir release schedules. For example, Jackson Lake dam was constructed in 1910 resulting in the impoundment of an additional 625,000 cubic feet of water. Since its construction and the establishment of Grand Teton National Park (GTNP), this water has been released during mid- to late summer months causing unpredictable fluctuations of river levels after the normal spring run off. This unpredictability is illustrated by the trend in water flow on the Snake River at Moran for the period 1904-2000 (Figure 1). A species that has received little attention in terms of population numbers and resistance to abnormal water fluctuations resulting from Jackson Dam is the beaver (Castor canadensis). In GTNP, only the work of Collins (1976) has provided any significant knowledge of the distribution and habitat of the beaver in the Park. In fact, the beaver has been generally overlooked in the Greater Yellowstone Area with only a few studies conducted in Yellowstone (Warren, 1926; Jonas, 1955; Consolo-Murphy and Hanson, 1993 ).
... Long-term inundation of forest stands will kill most flood-intolerant trees, converting riparian forests into wetlands. As these flooding impacts may be minimal or absent in lake environments (Collen and Gibson, 2000), the canopy impacts documented along lakes may more directly result from beaver foraging rather than the compounded forest disturbances of flooding, wetland expansion, and tree harvesting present along dammed streams. ...
Chapter
Hydrological and geomorphological processes are influenced by beaver (Castor canadensis and C. fiber) activities in aquatic and semi-aquatic environments throughout much of North America, Eurasia, and the austral archipelago of Chile and Argentina. The main hydrologic signature of beaver activities varies with hydrogeomorphic setting—along confined streams it is the pond formed upstream of dams, along unconfined streams it is downstream flooding on floodplains and terraces, and in preexisting wetlands it is the formation of open-water bodies. A review of the existing literature shows that it is rich with descriptions of how beaver activities influence specific hydrologic and geomorphic processes. The main findings are that beaver dams moderate stream flows, increase surface water and riparian groundwater storage, regulate hyporheic flows, and enhance evapotranspiration rates. Beavers also excavate canals on the margins of beaver ponds and create extensive burrow systems in riverbanks where damming is not possible. Bank burrows are also common in beaver ponds. Missing in the beaver hydrogeomorphological literature, however, are clear linkages between affected hydrological processes and ecosystem functioning, especially at larger spatial and temporal scales. In addition, knowledge of effects of beaver activities on the form and function of the expansive peatlands that span northern latitudes is lacking.
Article
Beaver dam mimicry is an emergent conservation practice. We evaluated the influence of constructed riffles, a unique type of beaver mimicry aimed to store water and allow fish passage, on habitat for fishes in one control reach and one manipulated reach with mimicry structures added. The beaver mimicry reach had deeper pool habitats and deeper and wider riffle habitats compared to an unmanipulated control reach. Dissolved oxygen was similar among reaches, averaging 8.7 ± 0.2 and 8.9 mg/L in the beaver mimicry and control reaches, respectively. Sediment size was also similar among reaches, with a D50 of 8.1 and 10.6 mm in the beaver mimicry and control reaches, respectively. The beaver mimicry reach had little to no overhanging bank vegetation or riparian vegetation shade cover, while the control had 38% of its bank covered by canopy and 56% overhung by vegetation. These riparian characteristics result from a legacy of livestock grazing and lack of consistent vegetation planting during restoration. Longnose dace (Rhinichthys cataractae) and white sucker (Catostomus commersonii) dominated in the beaver mimicry reach, together comprising 70% of the fish assemblage post‐structure installation. Arctic grayling (Thymallus arcticus) was not found in the beaver mimicry reach but was present in the control, albeit in small numbers of only 3% of the assemblage post‐structure installation. These results highlight the need to consider both in‐stream and riparian habitat features for fishes, as well as timescales of both hydrological and ecological outcomes in restoration design. We evaluated the influence of constructed riffles, a unique type of beaver mimicry aimed to store water and allow fish passage, on habitat for fishes. Longnose Dace and White Sucker dominated fish assemblages in the beaver mimicry reach. Arctic grayling were not found in the beaver mimicry reach but were present in the control.
Article
This study aimed to identify the composition of plant species and Useful plants in the forests of Taman Gumi Banten, Indonesia. This research conducted in the forests of Taman Gumi Banten and village Wanagiri. The population of this study, from the ecosystem aspect, is all plant species in the Taman Gumi Banten forest. From the sociosystem aspect, it is the entire community in Wanagiri village. The sample of this research from the ecosystem aspect is the plant species covered by squares. From the sociosystem aspect, it is a community component. The total sample is 50 people. Data collection methods are quadratic methods and interviews. The sampling technique is a systematic sampling technique. Data were analysed descriptively. The conclusions of this study are (1) There are 68 plant species in the entire forest of Taman Gumi Banten, (2) Of the 68 existing plant species, as many as 59 (86.76%) of the plant species were useful plants, while 9 (13.24%) of them were unknown. (5) The use of plants by the local community is 23 species (38.98%) for food, 20 species (33.89%) for boards, 9 species (15.25%) for medicine, 25 species (47.17%) ) for Hindu religious ceremonies, and industrial materials there are 1 species (1.69%).
Chapter
This chapter deals with the basic features of dam and hydropower projects, not from an engineering point of view, but aiming at identifying the main aspects which are of relevance for an impact assessment exercise. In the first section, a short description of the main types of dam and water intake structures is provided, mainly emphasising the difference between ROR (run-of-river) and storage plants.
Article
Successful species reintroduction requires restoration of receiving habitats to support growth, survival, and reproduction that reverse the initial causes of decline. Little is known about whether present habitat conditions can support all life stages of reintroduced southern Lake Sturgeon populations that were extirpated by the mid‐1900s due to overharvest and habitat degradation. Therefore, we conducted a telemetry study to assess annual adult and subadult and overwinter age‐0 Lake Sturgeon habitat selection and suitability in two Missouri River USA tributaries near the southern edge of the species range. Spring habitat selection models were unable to define spawning habitat criteria, but criteria from other studies suggest that substrate and depths for spawning are suitable in both rivers. In the summer and winter adult and subadult Lake Sturgeon exhibited strong selection for pools greater than 8 m deep, which comprised less than 5% of our study streams. Habitat selection in the fall and winter by age‐0 Lake Sturgeon differed from adults with age‐0s selecting shallower habitats both rivers and swifter current velocities in the Gasconade River. General habitat patterns persisted for both life stages in each river regardless of habitat availability, suggesting specialized habitat requirements in southern Lake Sturgeon that differ from previously studied populations further north. These results may be used to direct sampling for validation of reproduction and restoration of not only spawning habitats, but age‐0 and summer and winter refugia that may be potential restoration bottlenecks for southern Lake Sturgeon populations. This article is protected by copyright. All rights reserved.
Article
Beavers (Castor fiber, Castor canadensis) are one of the most influential mammalian ecosystem engineers, heavily modifying river corridor hydrology, geomorphology, nutrient cycling, and ecosystems. As an agent of disturbance, they achieve this first and foremost through dam construction, which impounds flow and increases the extent of open water, and from which all other landscape and ecosystem impacts follow. After a long period of local and regional eradication, beaver populations have been recovering and expanding throughout Europe and North America, as well as an introduced species in South America, prompting a need to comprehensively review the current state of knowledge on how beavers influence the structure and function of river corridors. Here, we synthesize the overall impacts on hydrology, geomorphology, biogeochemistry, and aquatic and terrestrial ecosystems. Our key findings are that a complex of beaver dams can increase surface and subsurface water storage, modify the reach scale partitioning of water budgets, allow site specific flood attenuation, alter low flow hydrology, increase evaporation, increase water and nutrient residence times, increase geomorphic heterogeneity, delay sediment transport, increase carbon, nutrient and sediment storage, expand the extent of anaerobic conditions and interfaces, increase the downstream export of dissolved organic carbon and ammonium, decrease the downstream export of nitrate, increase lotic to lentic habitat transitions and aquatic primary production, induce ‘reverse’ succession in riparian vegetation assemblages, and increase habitat complexity and biodiversity on reach scales. We then examine the key feedbacks and overlaps between these changes caused by beavers, where the decrease in longitudinal hydrologic connectivity create ponds and wetlands, transitions between lentic to lotic ecosystems, increase vertical hydraulic exchange gradients, and biogeochemical cycling per unit stream length, while increased lateral connectivity will determine the extent of open water area and wetland and littoral zone habitats, and induce changes in aquatic and terrestrial ecosystem assemblages. However, the extent of these impacts depends firstly on the hydro-geomorphic landscape context, which determines the extent of floodplain inundation, a key driver of subsequent changes to hydrologic, geomorphic, biogeochemical, and ecosystem dynamics. Secondly, it depends on the length of time beavers can sustain disturbance at a given site, which is constrained by top down (e.g. predation) and bottom up (e.g. competition) feedbacks, and ultimately determines the pathways of river corridor landscape and ecosystem succession following beaver abandonment. This outsized influence of beavers on river corridor processes and feedbacks is also fundamentally distinct from what occurs in their absence. Current river management and restoration practices are therefore open to re-examination in order to account for the impacts of beavers, both positive and negative, such that they can potentially accommodate and enhance the ecosystem engineering services they provide. It is hoped that our synthesis and holistic framework for evaluating beaver impacts can be used in this endeavor by river scientists and managers into the future as beaver populations continue to expand in both numbers and range.
Article
Abstract In this study I documented the results of 11 years of passive restoration of a small mountain stream in northeastern Oregon. Removal of the main stressors on the system, grazing and agricultural practices, resulted in a strong recovery of the riparian vegetation over the middle two thirds of the reach. Cover of trees and shrubs tripled, tree density increased sevenfold and stream shading fourfold over the period 2007–2018. Average maximum daily stream temperature declined by 2.1–2.8 oC and average maximum diurnal temperature range narrowed by 3.7–4.6 oC. Recolonizing American beavers (Castor canadensis) played an essential role in improving the condition of the streambed over 18% of the reach. Their dams and ponds initiated the process of streambed aggradation and transformed the single-thread, incised channel into a multi-thread configuration within beaver complexes. Vegetation expansion was much stronger in impounded than in un-impounded parts of the stream. Passive restoration was not effective in two sections together comprising one third of the reach. In the upper part of the stream recovery stalled because of continued (unauthorized) trespass grazing during late summer and fall. The channelized lower section of the stream was too severely modified for measurable recovery to occur. I concluded that 11 years of passive restoration improved the functionality of the stream from 24% to 32%, and within beaver complexes, up to 57% of its pre-disturbance condition.
Article
Full-text available
A biological model was developed to calculate annual survival between life stages of juvenile Atlantic salmon, Salmo salar L., in Catamaran Brook, a small stream basin (52 km2) in the Miramichi River catchment in New Brunswick, Canada. Seven years' (1990-1996) were used in the model. Input variables included: daily fish counts and measurements of parr (3-4 age classes), smolts, and adult salmon at a fish-counting fence near the stream mouth; biennial quantification of all habitat types along the watercourse; fish density estimated by electric fishing at 30 sites; and estimates of young-of-the-year emigration via s tream drift. Continuous recording of stream discharge provided data to assist in interpretation of survival estimates. Annual survival of juvenile salmon in their first 3 years of life in the stream average between 31% and 34%. The greatest annual variation (CV = 0.699) occurred at the egg to 0+ (summer) stage with a low of 9.2% survival recorded for a winter with an atypical midwinter flood event; parr and pre-smolt survival were similarly affected. Survival from egg deposition (after correction for losses caused by predation and retention/non-fertilization) to smolt emigration was between 0.16% and 0.52%, which is low relative to estimates from many other studies. Survival of smolts to return 1-sea-winter adults (grilse) averaged 8.5%. Potential errors in the computation of the model are discussed, e.g. inaccurate counts of spawning adults during high autumn stream flow. A possible explanation for the low egg to smolt survival was the environmental conditions experienced during various winters. Mean egg survival was 1.3 times higher (39.3%) and egg to smolt survival increased to 1.03% when the two winters characterized by extremely low discharge or midwinter freshets were excluded from the calculation. Density-dependent factors related to a beaver dam, which limited spawning distribution, may also have contributed to poor survival and increased fry emigration in one year. Environmental factors, particularly winter conditions, in streams such as Catamaran Brook may act as bottlenecks to natural production of Atlantic salmon.
Article
Full-text available
Lutra lutra, Mustela vison, M. putorius, M. erminea, M. nivalis, and the settlements of Castor fiber were surveyed along 170 km of rivers in Bialowieza Primeval Forest (Poland and Belarus), the best preserved temperate lowland forest in Europe. The censused rivers varied from very small (1-5 m wide, < 1 m deep) to medium-sized (11-15 m wide, up to 3 m deep). Mustelids were counted by tracks left in snow. Mean index of abundance of otters was 2.2 inds/10 km of the river bank (range 0- 5) and that of mink 4.6 inds/10 km (range 0-7.5). On average, 1.4 polecats/10 km were recorded (range 0-5). Otters and mink were most abundant on the medium- sized rivers and least numerous on very small ones. Polecats lived predominantly on very small rivers. Species structure of a predator guild varied with river size. On average, 5.1 stoats and 4.0 weasels were counted per 10 km of river bank. Stoats were twice as common along rivers with open marshy flood-plain as along rivers with forested valleys. On average, 2.9 beaver settlements were recorded per 10 km of river bank (range 0- 5). Habitat niche overlaps were highest between otter and mink, and stoat and mink. The smallest overlaps were between the polecat and all other predators. Densities of mustelid predators and beavers in Bialowieza Primeval Forest were similar to those in other fairly well preserved woodlands in Europe.
Article
Full-text available
Anthropogenic changes in stream geomorphology have reduced the capacity of many North American streams to trap and retain sediments and organic matter. Significant losses of retentive structures from many small streams have resulted from beaver trapping. We compared algal standing crops and rates of primary production in two adjacent streams in the Zuni Mountains of New Mexico. Castor Creek has been worked by beaver and is a complex, highly retentive system with an extensive floodplain and accumulations of organic debris. Sawmill Creek is moderately incised, free of large organic debris, and poorly retentive. Clay tiles introduced into Castor Creek had average chlorophyll a standing crops 3-9× greater than Sawmill Creek (54.8-257.8 vs. 18.4-44.9 mg/m2). Chlorophyll a on natural substrates averaged 11× greater in Castor Creek than in Sawmill Creek (1679.4 vs. 154.2 mg/m2). Average standing crop of chlorophyll a per 250 m reach was 136× greater in Castor Creek than in Sawmill Creek due to its greater surface area (12.4×) and greater standing crop (11×). Extensive filamentous algal mats and the macro-alga Nitella gracilis in Castor Creek's beaver ponds exhibited the highest rates of primary production (85 mg C m-2 hr-1) while epilithic samples from both streams were similar (16.6 and 21.2 mg C m-2 hr-1 for Castor and Sawmill Creeks respectively). Nutrient amendment experiments revealed that both streams were nitrogen limited. Sediment samples taken in 1989 showed Castor Creek had 25× more dissolved NH4 in the upper 5 cm of sediment than Sawmill Creek (1242 vs. 50 μg/L). We suggest that higher algal production in Castor Creek is linked to greater nutrient availability at the sediment/water interface due to greater retention and processing of organic matter in the hyporheic zone.
Article
Full-text available
In the boreal forest of northeastern Alberta, Canada, we investigated the contention that, during winter, river otters (Lutra canadensis) lower water levels in ponds created by beavers (Castor canadensis). Ponds not visited by otters (control ponds) and ponds visited by unmarked otters or otters instrumented with implanted radio transmitters, were investigated for sites of water loss through dams. Both otters' ability to enter ponds through ice and pass through dams under ice, as evidenced by radiotelemetry and snow-tracking, were significantly associated with net water loss from ponds and with distinctive sites of water loss—trenches cut through dams. Trenches were not found in control ponds. Sticks exposed in dam passages penetrated by otters had parallel grooves separated by distances similar to those separating canine teeth on otter skulls. We conclude that otters dig passages through dams to insure under-ice access between adjacent water bodies. Possible secondary benefits may include increased access to air under ice, and more highly concentrated prey. Beavers repair most passages during times of open water. A partial commensalism appears to exist with otters benefitting from creation and maintenance of fish habitats by beavers.
Article
Full-text available
We sampled stream fishes within and at varying distances from beaver ponds for two years in two southeastern blackwater streams. Our objectives were to determine whether species showed ontogenetic or seasonal shifts in habitat use involving impounded and free-flowing stream reaches and whether assemblage structure and dynamics varied between ponds and streams and as a function of upstream distance from ponds. Age-0 and adults of most of the more abundant species (15) were collected in either streams or ponds, suggesting no ontogenetic or seasonal shifts in habitat use for these species. The proportions of age-0 to adult fish of four species were higher in ponds than streams, suggesting movement of adults to ponds to breed. The proportion of age-0 to adult Erimyzon oblongus was higher in streams when compared to ponds, suggesting adults of this species supplement food resources by feeding in ponds. Assemblage structure was less stable in ponds when compared to streams. In streams, age-0 and adult fish densities and population co-efficients of variation (CV) declined with upstream distance from ponds. Because high CVs were typical of species occurring in streams throughout their life, and habitat structure and variability were not related to upstream distance from ponds, interactions between pond boundaries and fish movement are probably responsible for the patterns we observed in streams adjacent to ponds.
Article
Basic factors determining numbers of the river beaver near the northern limit of the species' geographic range were studied. Feeding conditions and anthropogenic factors are most important. Comprehensive management of the coastal zone is recommended to reduce the negative influence of man on numbers of beaver.-Journal summary
Article
Between 1952 and 1961 standing crops of brook (Salvelinus fontinalis), rainbow (Salmo gairdneri), and brown (Salmo trutta) trout were determined in August for a 5.7 mile section of Sagehen Creek in east-central California. In 1953 a creel census was initiated which continued through 1961. The purpose of the study was to determine if a moderately productive wild trout stream could support a substantial angler harvest over an extended period without augmentation with hatchery-reared trout. The 10-year average standing crop of all trout was 1, 578 (37 pounds) per acre. Standing crops declined somewhat during the study period, largely due to habitat deterioration rather than to fishing. Floods and abandonment of beaver impoundments were the primary adverse influences on trout habitat. Catch did not decline significantly over the period. Fishermen annually removed 23-47% (average, 33%) of all trout over 99 mm in length, but recruitment replaced the loss. Although the natural fishery has proven to be viable, the trout population is not characterized by many large fish. We recommend an experimental management program aimed at (1) restoring some of the brown trout habitat by construction of low dams similar to the beaver dams that formerly were so productive, and (2) increasing the number of larger trout in the stream by regulation of the take. If each iarge trout is subject to multiple capture and release, additional high-quality sport would be provided. Future studies could evaluate the effect on the fishery of these changes in management.
Article
Strychnine alkaloid baits were consumed by both captive and wild beaver without any apparent hesitation. An approximate minimal acute lethal dose of sodium monofluoro-acetate to beaver of mixed ages and sex was 0.202 mg/kg. Trapping beaver on four study area watersheds in Alabama with No. 330 conibear traps for approximately two weeks in winter during two successive years essentially eliminated beaver. Older individuals were trapped the first year, maturing juveniles and the remaining few adults were trapped the second year, and there was very little reproduction between the trapping periods. Trapping, with its recreational appeal, and income and food potential seems the better and more prudent approach to control of nuisance beaver than others being considered.
Article
The constructive behaviour of the beaver can be studied from the many lodges, dams and canals which it has built. In beaver behaviour we can also study the fixed patterns in every action related to construction to show how the beaver distinguishes itself from other builder mammals. Innate/automatic behaviour is distinguished from behavioural responses to external circumstances.-from Author
Article
In the NW USSR reintroduction of beavers began in 1934. In the early 1950s Canadian beavers penetrated the territory of Karelia and the Karelian Isthmus from Finland. Moving swiftly S and E they occupied a considerable part of the territory. At present there are >300 settlements of Canadian beavers totalling 1700-2000 animals. European and Canadian beavers have similar feeding habits: aspen, willow and birch are the main diet. The Canadian beaver is highly active in building shelters and dams. Lodges are found in 104 (74.8%), settlements and dams in 93: 160 (32.8%) and 261, respectively for the European beaver. The most substantial differences are traced in comparing reproductive characteristics. In the European beaver only 7-8% of females reproduce at the age of 1.5-2yr, in the Canadian up to 20%; and 50-60% of adult European beaver females are involved in reproduction against 70-80% of the Canadian beaver. Average fertility (number of kits in a litter) is 1.9 for the European beaver and 3.2 for the Canadian beaver. - Authors
Article
The risk of accidental introduction of coho salmon in rivers inhabited by Atlantic salmon induced research on competition mechanisms between fry and juveniles of the two species under experimental conditions. Possible consequences of the competition were evaluated in terms of survival, growth, predation, downstream movement and habitat use. Results showed that under good trophic conditions, the presence of coho salmon had no influence on Atlantic salmon fry and juveniles. Microdistribution was different, Atlantic salmon holding position in riffles and coho salmon preferring pools. The pelagic and gregarious behaviour of coho salmon juveniles, that are much larger than Atlantic salmon at the same stage after emergence, contrasted with the benthic substrate-bound behaviour of the latter. These differences increased in sympatry at the expense of Atlantic salmon, which was handicapped by its smaller size. Under limiting trophic conditions, the growth and sedentary behaviour of Atlantic salmon were significantly altered by the presence of coho salmon, thus justifying explicit doubt on the interest of introducing coho salmon into French rivers.
Article
Population changes in Isle Royale beavers Castor canadensis and some aspects of their relationships with predators, disease, and competitors for food are described. Abundant food resources allowed a high population to develop by 1950, after which a decline occurred, probably due to tularemia. A 2nd increase through the 1960's was followed by a decline, caused by heavy wolf Canis lupus predation, in the 1970's. Competition with moose Alces alces for food, declining food resources, and continued wolf predation may prevent the population from again reaching high numbers. -Authors
Article
The beaver appears at Upper Miocene, then becomes widespread from W to E in the whole Holarctic zone. Following hunting, by the start of the 20th century populations were low and scattered. These persist until now and serve to numerous reintroductions. C. canadensis, which were introduced in Finland and in USSR, have tended to invade. -from English summary
Article
Bobry pojawily sie w Szwecji okolo 6000 lat p.n.e. W ciągu nastepnych tysiącleci rozprzestrzenily sie w odpowiednich biotopach na terenie calego kraju. Zmiany klimatu, jakie zaszly okolo 500 lat p.n.e. spowodowaly wytworzenie sie duzych obszrow wilgotnych lasow, co sprzyjalo bytowaniu bobrow. Az do XIII i XIV w. bobr spotykany byl w calej Szwecji, lecz w tym czasie wydaje sie byc rzadszy w trzech najbardziej poludniowych prowincjach. W pozostalych cześciach Szwecji bobry byly pospolite jeszcze w wieku XV i XVI, ale juz w XVII wieku ilośc eksportowanych skorek ulega obnizeniu.
Article
The effect of beaver Castor canadensis flood on the riparian vegetation, aquatic invertebrates and waterfowl broods of a creek was studied in S Finland in a barren watershed area. The creek was monitored before artificial damming in 1984 and thereafter during the first 3yr of inundation. As early as 1985, grey alders Alnus incana exhibited pronounced signs of stress, whereas willows Salix spp were still in fairly good conditions in 1987. Most of the macrophyte stands became considerably thinner, although the species composition was not radically altered. Potentilla palustris tolerated flooding very well. In the littoral, the most numerous macrobenthic forms were chironomids and Asellus. In the river bed Pisidium abounded, together with chironomids. The limnic forms of the littoral, particularly Eurycercus, were most abundant during the first year of flooding. Beaver can act as a keystone species by affecting the structure of riparian communities. Waterfowl can take advantage of these changes. -from Author
Article
W dawniejszych czasach bobry zasiedlaly na obecnym terenie ZSRR prawie calą strefe lasow wchodząc wzdluz rzek w strefe lasostepow i stepow. Obecnie zachowaly sie tylko w nielicznych, odleglych od siebie miejscach. Ochrona i reaklimatyzacja bobrow doprowadzily do wzrostu liczebności do 40 000 sztuk (1964 rok), w porownaniu z 900 osobnikami jakie notowano w latach dwudziestych biezącego stulecia.
Article
Dane paleontologiczne wskazują, ze bobry zamieszkują Finlandie od 6500-7000 lat. Intensywne lowienie tych zwierząt spowodowalo, ze ostatni osobnik zostal zabity w polnocnej Finlandii w 1868 r. Dopiero w latach 1935-36 przywieziono 19 bobrow europejskich z Norwegii, a w 1937 7 bobrow kanadyjskich ze stanu New Jork. Ten drugi gatunek szybko zwiekszal swą liczebnośc tak, ze od 1945 roku mozna bylo go przewozic w inne regiony kraju.
Article
In the autumn-spring seasons of 1976—77 and 1984—85, an inventory of beaver sites was made in the Suwalki Lakeland. The respective numbers of the sites recorded were 137 and 257. The increase in the number of sites was due to their higher density in the earlier occupied areas and to the expansion of beavers westwards and southwards. The most preferred habitats of beavers were lakes and rivers (1976—77: lakes 43°/o, rivers 47°/o; 1984—85: lakes 49%, rivers 38%). Females produced 1.7 young per litter, and 68% of pairs reproduced. In 1977—85, 217 beavers were captured in the Suwalki Lakeland. It has been found that a high proportion (56%) of beavers had black hair, females slightly outnumbered males (54 :46), and the proportion of adults was high in the population. Adult females were heavier than adult males. Young beavers gained weight during their first winter, whereas the weight of adults decreased during winter. The beaver population of the Suwalki Lakeland enters a stable phase, and soon an annual reduction of animal numbers will be needed.
Article
In the autumn of 1977 and 1978, SOTRAC made aerial inventories of Castor canadensis lodges in the 2600km2 area scheduled to be flooded by the LG 2 Reservoir. In summer 1978, SOTRAC transplanted 170 beaver into 3 traplines located outside the inundation area of the Opinaca Reservoir. Ten of the transplanted beaver were equipped with radio transmitters to follow their movements. To study the behavior of beaver as the water level rose during the impoundment of a reservoir, 9 beaver were radio marked and are being monitored since their release.-from Authors
Article
W oparciu o dane z literatury oraz wyniki ankiety przeprowadzonej w latach 1964-1965, określono przepisy lowieckie, statystyki pozyskania oraz rozmieszczenie i wielkośc populacji w ciągu wielu lat, wymogi środowiskowe, pozywienie, budowle oraz szkodliwą dzialalnośc bobra, Castor fiber Linnaeus, 1758 w Norwegii.
Article
Road strip counts were tested in Livingstone Game Park, Northern Rhodesia, for censusing a known population of various species of African ungulates. For the smaller or more wary species, populations were greatly underestimated. For the larger more conspicuous species, populations were underestimated also when mean sight distances were used to determine strip widths. The use of other methods for determining strip width
Article
The food habits of the lynx (Lynx canadensis) on the Island of Newfoundland were investigated during the period 1956-61. Results are based upon analyses of the contents of 206 digestive tracts, 116 identified lynx scats, and 104 presumed lynx scats. Snowshoe hares (Lepus americanus) occurred in 73 percent of the total tracts and scats in all seasons. Birds, especially smaller species, occurred in 21 percent of the material but were taken most in spring and summer. Mice occurred in 14 percent of the material during snow-free periods of years when they were abundant. Carrion resulting from big game hunting occurred in 20 percent of the tracts and scats, principally during fall and winter. Little evidence of predation upon domestic animals was found. Information on hunting habits of lynx, obtained from tracking studies, is presented.
Article
Waterfowl use was recorded in 1965 and 1966 at different elevations of the Uinta Mountains, Utah, from spring thaw until fall freeze-up. Sixteen species were observed; mallard (Anas platyrhynchos), green-winged teal (A. crecca), pintail (A. acuta), and ring-necked duck (Aythya collaris) were the most abundant. Ninety-eight percent of the observed waterfowl were below 3,000 m. Waterfowl numbers were highest during migratory periods and lowest in the breeding season. Adult waterfowl were seen most often on natural catchment basins and beaver (Castor canadensis) ponds larger than 0.4 ha. Low-elevation wetlands (<2,600 m) had high indices of aquatic invertebrates and contained aquatic plants with high seed-producing capabilities, whereas high-elevation wetlands (>2,900 m) had little waterfowl food. Utilization of high mountain wetlands by spring migrants and breeders was dependent upon ice melt, whereas freeze-up did not seriously affect fall use.
Article
We developed a model predicting occurrence of river otters (Lutra canadensis) by comparing 19 watersheds used by otters with 14 unused watersheds during 1985-87. Of 39 habitat variables initially measured, 4 provided good discrimination between used and unused watersheds. Otter use was negatively associated with the proportion of mixed hardwood-softwood stands in forested areas adjacent to waterways and positively associated with the number of beaver flowages, watershed length, and average shoreline diversity. Our model correctly classified 94% of the watersheds and demonstrated 88% better classification than could be achieved by chance alone.
Article
The relationship between sizes of trees cut by beavers and distances from the borders of their ponds was examined at three sites in central Massachusetts. For most tree genera, the beavers cut a smaller range of sizes far from shore than close to shore, and relatively more small trees and fewer large trees at greater distances. The second of these results differs from the pattern of preference found in other studies in which predators were much larger than their prey, unlike this case of beavers feeding on trees. Both kinds of results are consistent with an optimal foraging model of size-distance relations in which pursuit or provisioning time depends on size of prey as well as distance (Schoener 1979).
Article
Although breeding activity in a colony of beaver (Castor canadensis) usually is confined to an adult pair, sexually mature male and female progeny are present and may reproduce if 1 or both adults are removed. To assess behavior and reproduction in such progeny, 1 adult in each of 18 colonies was either surgically sterilized or sham-operated in summer 1975. Sterility was induced by either tubal ligation (5♂, 5♀ in 10 colonies) or castration (2♂, 2♀ in 4 colonies); sham operations were performed in 4 colonies (2♂, 2♀). Behavioral and reproductive responses were normal in sham-operated controls, but 11 of 13 sterilized colonies had no reproduction by beaver. The 14th colony dispersed before parturition could have occurred. Reproduction occurred in 1 of 10 colonies with ligated adults, 1 of 4 with castrated adults, and 4 of 4 with sham-operated adults. Sterilization of either adult in a colony significantly reduces fecundity, yet permits maintenance of an established colony with its associated benefits. Breeding inhibition is discussed with respect to population density, dispersal of 2-year-olds, and beaver management.
Article
The Newfoundland beaver Castor canadensis caecator has flourished in an area that lacks abundant supplies of those plant species normally considered to be preferred food. Aspects of the utilization of vegetation by beavers are described on the basis of field studies conducted during periods of 1961, 1962 and 1963 in three areas of the province. Where aspen Populus tremuloides occurs, always in small amounts, it is soon utilized completely. Alders Alnus rugosa and A. crispa are the most important plants, being the chief winter food and the major building material. Aquatic vegetation, particularly the water lilies Nuphar variegatum and N. microphyllum, is the major constituent of the summer diet.
Article
Seasonal variation in food of the beaver (Caster canadensis Kuhl) was examined on the Mackenzie Delta, Northwest Territories, Canada. Leaves and, to a lesser extent, growing tips of willow (Salix spp.) were the main food items during July and August; during the remaining 10 months food consisted of the bark of willow (76%), poplar (Populus balsamifera) (14%) and alder (Alnus crispa) (10%). Protein: calorie ratios in the diet were approximately 40 and 8 mg/cal during those two periods respectively. The northern beaver has adapted to low energy availability characteristic of winter by storing food in the autumn and again in the spring, and by intrinsically lowering food intake during the winter. It has adapted to seasonal variation in protein availability by utilizing high-protein willow leaves almost exclusively when they are available. The heavy dependence upon willow, and its resultant removal from the community, can impart a high degree of instability to northern beaver populations.
Article
I combined long-term (10 yr) descriptive and short-term experimental studies in a headwater stream in northern Minnesota to assess: (1) the effect of annual variation in stream discharge and spatial proximity of beaver (Castor canadensis) ponds on lotic fish abundance and (2) the subsequent influence of discharge and fish predation on lotic invertebrate colonization. Considerable annual variation in fish density occurred in the stream over the 10-yr period, particularly in pool habitats. Increased fish density was associated with increased stream discharge and creation of beaver ponds downstream from the study site. Wiegert traps used to monitor directional (upstream vs. downstream) fish movement during the last 4 yr of the study indicated annual changes in fish density were associated with the amount of fish dispersal occurring along the stream segment. Downstream fish movement, out of an upstream beaver pond occurred primarily during periods of elevated stream discharge. Upstream movement, out of a downstream beaver pond, occurred over a broader range of discharge conditions. A controlled, @'slpit-stream,@' experiment examining the effect of very low vs. elevated discharge on upstream fish movement indicated, however, that upstream movement of fish out of beaver ponds was also reduced by very low discharge conditions. Movement data for individual fish species revealed considerable variation among the taxa in the tendency for downstream vs. upstream movement, due to variation in the morphology of upstream vs. downstream beaver ponds and its subsequent effects on the composition of fish dispersing from these source areas. Most fish movement occurred over relatively brief time periods, suggesting life history and developmental processes were critical in influencing the timing of dispersal. Size structure of fishes captured in the stream indicated predominantly older age classes (>age I) of fish where dispersing along the stream. However, based on the occurrence of age O individuals only 1 of 12 species, the creek chub Semotilus atromaculatus), routinely reproduced in the stream. Experiments conducted in an artificial stream located below one of the beaver ponds indicated discharge and fish predation have potentially strong and interactive effects on invertebrate colonization in stream ecosystems. Differences in colonization of riffles and pools under low vs. elevated discharge and fish vs. no-fish treatments suggested, however, that the interactive effect of these factors on invertebrate colonization was variable over even small spatial scales. Elevated discharge increased invertebrate colonization in riffles but decreased invertebrate colonization in pools. Contrary to intuitive expectations, fish predation reduced invertebrate colonization more under elevated than low discharge conditions, particularly in pool habitats. Taken together, these results: (1) beaver ponds act as reproductive @'sources@' for fish on the landscape, while adjacent stream environments act as potential reproductive @'sinks,@' (2) large-scale spatial relationships between beaver ponds and streams, along with the influence of discharge on the permeability of the boundaries between these habitats, are critical in controlling fish dispersal between ponds and streams and the subsequent abundance and composition of fish in lotic ecosystems, and (3) fish predation and discharge have potentially cascading effects on invertebrate colonization in lotic ecosystems.
Article
Through dam building and feeding activities, beaver act as a keystone species to alter hydrology, channel geomorphology, biogeochemical pathways and community productivity. In Quebec, density of dams on the small streams (= or <4th order) studied averages 10.6 dams/km; the streams retain up to 6500 m3 of sediment per dam, and the wetted surface area of the channel is increased up to several hundredfold. Beaver are also active in larger order streams (= or >5th order), but their effects are most noticeable along riverbanks and in floodplains. Comparative carbon budgets per unit area for a riffle on 2nd order Beaver Creek and a beaver pond downstream show the pond receives only 42% of the carbon acquired by the riffle annually, but because the pond has a surface area 7 times greater than the riffle, it receives nearly twice as much carbon as the riffle per unit of channel length. Carbon in the pond has an estimated turnover time of 161 yr compared to 24 yr for the riffle. Beaver ponds are important sites for organic matter processing. -from Authors