Reintroduction of beavers <Emphasis Type="Italic">Castor fiber</Emphasis> may improve habitat quality for vespertilionid bats foraging in small river valleys

Beavers strongly modify their environment by not only building dams and creating ponds, which slow the water flow, but also by selective cutting and removing of trees, which change the spatial structure of the forest. We aimed to test the hypothesis that beaver activity promotes new foraging sites for insectivorous bats. The beaver’s influence can be especially significant on aerial hawkers that prefer moderate structural clutter, like the Pipistrellus species (by creating new canopy gaps), and on water-surface foragers, like Myotis daubentonii (by creating ponds with smooth water surface). The study was conducted on small streams in forest areas of northern Poland, which were colonized by the European beaver (Castor fiber). Bat activity was recorded with a Pettersson D-980 ultrasound detector on line transects. The number of bat passes was significantly higher in the stream sections modified by beavers (flooded and subjected to intensive tree cutting) than in the unmodified sections (for Pipistrellus nathusii, Pipistrellus pipistrellus, Pipistrellus pygmaeus, Nyctalus noctula, and all species lumped together). Contrary to our expectations, the activity of the Myotis species was significantly lower on the transect with the largest beaver ponds, possibly due to the blanket of duckweed (Lemnaceae), which is known to produce clutter echoes, thereby reducing prey detection by echolocating M. daubentonii.     

Beavers alter stream macroinvertebrate communities in north-eastern Utah

1. Understanding changes in macroinvertebrate communities is important because they play a large role in stream ecosystem functioning, and they are an important food resource for fish. Beaver-induced changes to stream morphology could alter macroinvertebrate communities, which in turn could affect food webs and ecosystem function. However, studies investigating the effects of North American beaver activities on macroinvertebrates are rare in the inter-mountain west, an area with high potential for beaver-assisted restoration.
2. The aim of this study was to quantify differences in the macroinvertebrate community between unaltered segments of streams and within beaver ponds in north-eastern Utah, U.S.A. We assessed macroinvertebrate species richness, biomass, density, functional feeding group composition, mobility group composition, and macroinvertebrate habitat characteristics to test the hypothesis that macroinvertebrate communities will differ among habitat types (undammed stream segments and beaver ponds) in beaver-occupied streams.
3. Beaver pond communities significantly differed from lotic reach communities in many ways. Beaver ponds were less diverse with 25% fewer species. Although there was variability among streams, in general, beaver ponds had 75% fewer individuals and 90% lower total macroinvertebrate biomass compared to lotic reaches.
4. Regarding functional feeding groups, beaver ponds contained more engulfers, while lotic reaches contained more scrapers, filterers, and gatherers. For mobility groups, beaver ponds had more sprawlers, while lotic reaches had more clingers. Swimmers were also more prevalent in lotic reaches, although this is probably due to the abundance of Baetis within lotic reaches. More beaver pond taxa were classified as lentic-dwelling insects, while more lotic reach taxa were categorised as preferring lotic habitats.
5. The creation of ponds by beavers fundamentally altered the macroinvertebrate community in north-eastern Utah streams. Such changes to stream macroinvertebrate communities suggest that recolonisation of beavers across North America may be altering stream functioning and food webs. Our study highlights the need to further investigate the effects of beaver recolonisation on stream communities.

     

Pond-Breeding Amphibian Species Richness and Habitat Selection in a Beaver-Modified Landscape

ABSTRACT Beaver (Castor canadensis) activity creates wetland habitats with varying hydroperiods important in maintaining habitat diversity for pond-breeding amphibians with significantly different breeding habitat requirements. We documented pond-breeding amphibian assemblages in 71 freshwater wetlands in Acadia National Park, Maine, USA. Using 15 variables describing local pond conditions and wetland landscape characteristics, we developed a priori models to predict sites with high amphibian species richness and used model selection with Akaike's Information Criterion to judge the strength of evidence supporting each model. We developed single-species models to predict wood frog (Rana sylvatica), bullfrog (R. catesbeiana), and pickerel frog (R. palustris) breeding site selection. Sites with high species richness were best predicted by 1) connectivity of wetlands in the landscape through stream corridors and 2) wetland modification by beaver. Wood frog breeding habitat was best predicted by temporary hydroperiod, lack of fish, and absence of current beaver activity. Wood frog breeding was present in abandoned beaver wetlands nearly as often as in nonbeaver wetlands. Bullfrog breeding was limited to active beaver wetlands with fish and permanent water. Pickerel frog breeding sites were best predicted by connectivity through stream corridors within the landscape. As beavers have recolonized areas of their former range in North America, they have increased the number and diversity of available breeding sites in the landscape for pond-breeding amphibians. The resulting mosaic of active and abandoned beaver wetlands both supports rich amphibian assemblages and provides suitable breeding habitat for species with differing habitat requirements. Land managers should consider the potential benefits of minimal management of beavers in promoting and conserving amphibian and wetland diversity at a landscape scale.     

Tundra be dammed: Beaver colonization of the Arctic

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

Beaver herbivory on aquatic plants

Herbivores have strong impacts on marine and terrestrial plant communities, but their impact is less well studied in benthic freshwater systems. For example, North American beavers (Castor canadensis) eat both woody and non-woody plants and focus almost exclusively on the latter in summer months, yet their impacts on non-woody plants are generally attributed to ecosystem engineering rather than herbivory. Here, we excluded beavers from areas of two beaver wetlands for over 2 years and demonstrated that beaver herbivory reduced aquatic plant biomass by 60%, plant litter by 75%, and dramatically shifted plant species composition. The perennial forb lizard’s tail (Saururus cernuus) comprised less than 5% of plant biomass in areas open to beaver grazing but greater than 50% of plant biomass in beaver exclusions. This shift was likely due to direct herbivory, as beavers preferentially consumed lizard’s tail over other plants in a field feeding assay. Beaver herbivory also reduced the abundance of the invasive aquatic plant Myriophyllum aquaticum by nearly 90%, consistent with recent evidence that native generalist herbivores provide biotic resistance against exotic plant invasions. Beaver herbivory also had indirect effects on plant interactions in this community. The palatable plant lizard’s tail was 3 times more frequent and 10 times more abundant inside woolgrass (Scirpus cyperinus) tussocks than in spatially paired locations lacking tussocks. When the protective foliage of the woolgrass was removed without exclusion cages, beavers consumed nearly half of the lizard’s tail leaves within 2 weeks. In contrast, leaf abundance increased by 73–93% in the treatments retaining woolgrass or protected by a cage. Thus, woolgrass tussocks were as effective as cages at excluding beaver foraging and provided lizard’s tail plants an associational refuge from beaver herbivory. These results suggest that beaver herbivory has strong direct and indirect impacts on populations and communities of herbaceous aquatic plants and extends the consequences of beaver activities beyond ecosystem engineering.     

The influence of Eurasian beaver Castor fiber activity on fish assemblages in small steppe rivers in Russia

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.

     

The importance of aquatic vegetation in beaver diets and the seasonal and habitat specificity of aquatic‐terrestrial ecosystem linkages in a subarctic environment

The extent and ecological significance of trophic linkages across ecosystem boundaries have been the subject of considerable recent research attention. North American beavers Castor canadensis engineer terrestrial influences in aquatic ecosystems by constructing terrestrial food caches near their lodges and aquatic influences in terrestrial ecosystems by building dams and flooding low lying areas. However, it is poorly resolved to what extent beavers rely on aquatic food sources and whether this reliance is greater during winter when ice cover physically confines beavers to aquatic habitats or during summer when warm, ice free water promotes the growth and accessibility of aquatic vegetation. Working in a subarctic region, we surveyed the abundance of aquatic and terrestrial food sources in and around lotic and lentic environments and estimated their contributions to beaver diets during open water and ice covered periods using carbon and nitrogen stable isotope analysis of hair samples. Ponds had four times more aquatic vegetation than streams, but terrestrial habitats around ponds had less than half as much shrub cover as habitats adjacent to streams. Beaver diets in this subarctic environment are estimated to be comprised of 60 to 80% aquatic vegetation, with beavers occupying ponds consuming more aquatic vegetation in winter than beavers occupying streams, which rely more on terrestrial shrubs cached near their lodge. Collectively, these results show how the influence of physical barriers on ecosystem linkages can be modified by habitat‐ and season‐specific abundances of preferred resources and the potential for animals to consume food in ecosystems and seasons different from where and when the food was harvested.     

Ecosystem engineering by invasive exotic beavers reduces in-stream diversity and enhances ecosystem function in Cape Horn,Chile

Species invasions are of global significance, but predicting their impacts can be difficult. Introduced ecosystem engineers, however, provide an opportunity to test the underlying mechanisms that may be common to all invasive engineers and link relationships between changes in diversity and ecosystem function, thereby providing explanatory power for observed ecological patterns. Here we test specific predictions for an invasive ecosystem engineer by quantifying the impacts of habitat and resource modifications caused by North American beavers (Castor canadensis) on aquatic macroinvertebrate community structure and stream ecosystem function in the Cape Horn Biosphere Reserve, Chile. We compared responses to beavers in three habitat types: (1) forested (unimpacted) stream reaches, (2) beaver ponds, and (3) sites immediately downstream of beaver dams in four streams. We found that beaver engineering in ponds created taxonomically simplified, but more productive, benthic macroinvertebrate assemblages. Specifically, macroinvertebrate richness, diversity and number of functional feeding groups were reduced by half, while abundance, biomass and secondary production increased three- to fivefold in beaver ponds compared to forested sites. Reaches downstream of beaver ponds were very similar to natural forested sections. Beaver invasion effects on both community and ecosystem parameters occurred predominantly via increased retention of fine particulate organic matter, which was associated with reduced macroinvertebrate richness and diversity (via homogenization of benthic microhabitat) and increased macroinvertebrate biomass and production (via greater food availability). Beaver modifications to macroinvertebrate community structure were largely confined to ponds, but increased benthic production in beaver-modified habitats adds to energy retention and flow for the entire stream ecosystem. Furthermore, the effects of beavers on taxa richness (negative) and measures of macroinvertebrate biomass (positive) were inversely related. Thus, while a generally positive relationship between diversity and ecosystem function has been found in a variety of systems, this work shows how they can be decoupled by responding to alterative mechanisms. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Recovery and status of native and introduced beavers Castor fiber and Castor canadensis in France and neighbouring countries

• 1 The Eurasian beaver Castor fiber suffered a drastic reduction in both geographical range and population size, due to human persecution, until the end of the 19th century. After the adoption of protection measures, natural expansion and reintroductions led to the recovery of this species over much of its European range.
• 2 We review historical events that led to the recovery of beavers in France, and summarize the status of beavers in various river systems. Beaver establishment in France is a story of overall success: several major river systems are presently occupied, so that the species is no longer at risk in France.
• 3 However, beaver recolonization took place in parallel with increasing human impacts on the environment. In addition to natural limiting factors, anthropogenic factors impeded beaver settlement in many areas. Today, beavers often occupy suboptimal habitats and, as a consequence, come into conflict with human activities. Effective solutions for preventing beaver damage include the restoration of riparian habitats to discourage crop damage and the provision of physical barriers to protect crops.
• 4 Beaver populations reintroduced into France all originate from the relict Rhône population. However, in recent years, beavers from populations in neighbouring countries have been expanding into north‐eastern France. Therefore, our review of beaver origin and distribution in these countries may contribute to the development of appropriate national management strategies and towards important decisions, e.g. the decision to try to keep Rhône beavers genetically isolated, or to allow populations to mix.
• 5 The recently discovered presence of North American beavers Castor canadensis in three countries surrounding France has raised an important issue. This species may out‐compete C. fiber in places where the species come into contact. A programme based on field‐trapping sessions and genetic analyses has recently been initiated in some western countries in order to eradicate this non‐native species.

     

Influences of Landscape Features on Bat Activity in North Dakota

Land conversion and modification threatens many wildlife and plant species in the northern Great Plains, including bats. Our objective was to assess the association of bat species with landscape features in the northern Great Plains of North Dakota, USA, taking the first step towards understanding the habitat needs of bats in this region. We examined patterns of bat activity across different landscapes, identified those landscape features associated with high levels of bat activity, and determined which specific land features (i.e., vegetation and water types) were most commonly associated with each bat species. We used passive acoustic monitoring to measure bat activity at sites across North Dakota, and assessed detailed land characteristics at each site. We used nonmetric multidimensional scaling and multivariate regression tree analysis to examine relationships between bat activity and landscape variables. Bat foraging activity was influenced by structural landscape characteristics and the availability of specific water resources. High levels of bat activity were associated with riparian forested areas of varying structural complexity, ponds, and, to a lesser extent, open riparian lands. Individual bat species were influenced by land type and water resources differently. We identified big brown bats (Eptesicus fuscus) and little brown bats (Myotis lucifugus) as indicators of open riparian and pond landscapes, respectively. These results highlight the importance of prairie riparian landscapes and maintaining heterogeneity across the landscape for conservation and management of bat communities. Further, we identified ponds as an important landscape feature for little brown bats, a species of conservation concern, indicating that this specific feature should be a focus of conservation efforts on prairie wetlands. © 2019 The Wildlife Society.     

Beavers (Castor canadensis) influence habitat for juvenile salmon in a large Alaskan river floodplain

Our aim was to determine how beavers affect habitats and food resources for juvenile salmon in the Kwethluk River in western Alaska.

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Habitat engineering by beaver benefits aquatic biodiversity and ecosystem processes in agricultural streams

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Lowland boreal forests characterization in Algonquin Provincial Park relative to beaver (Castor canadensis) foraging and edaphic factors

Beaver (Caster canadensis) foraging and edaphic conditions can modify the vegetational characteristics of woody plant community in lowland boreal forests. Effective management of these areas requires an understanding of the relative contribution of these factors in shaping the woody plant community structure. Our objective was to quantify the effects of herbivory by beavers and edaphic conditions on woody plant community organization of lowland boreal forests surrounding beaver ponds. Woody vegetation and soils were sampled at 15 ponds occupied by beavers and one other pond abandoned by them in southern Algonquin Park, Ontario. We measured spatial variation in plant diversity, foraging rates and sapling recruitment of trees and shrubs along gradients of beaver foraging intensity and soil moisture, P, K, Mg, and pH. Beavers fed preferentially on a small number of deciduous species and the number of cut stems declined sharply with increasing distance from ponds. Conifers increased in relative dominance to deciduous species in the presence of beavers. Plant species richness and stem and basal area diversity peaked at intermediate distances (about 25 m) from ponds. Sapling recruitment by non-preferred species was positively related to foraging intensity. Total stem abundance and basal area and sapling recruitment by four preferred species (Populus tremuloides, Acer rubrum, Acer saccharum and Corylus cornuta) were negatively related to foraging intensity. However, by including Alnus rugosa and Salix bebbiana (also preferred by beavers) these patterns changed, becoming positively related to foraging intensity. There was also a pronounced gradient in soil moisture, which also decreased with distance from ponds. The other measured edaphic variables did not vary consistently with distance from ponds. Sapling recruitment in mesic versus xeric species varied consistently with hydrid conditions along the moisture gradient, such that variation in moisture also could produce the observed pattern of plant diversity. Diversity patterns changed three years after beaver abandonment of a pond, though sapling recruitment patterns in preferred and non-preferred species around the abandoned pond were similar to the occupied ponds. These observations suggest spatial variation in woody plant richness and diversity could be determined by combined effects of both herbivory (disturbance by beavers) and variable responses of different species to edaphic conditions.     

Livestock grazing limits beaver restoration in northern New Mexico

The North American beaver (Castor canadensis) builds dams that pond water on streams, which provide crucial ecological services to aquatic and riparian ecosystems and enhance biodiversity. Consequently, there is increasing interest in restoring beavers to locations where they historically occurred, particularly in the arid western United States. However, despite often intensive efforts to reintroduce beavers into areas where they were severely reduced in numbers or eliminated due to overharvesting in the eighteenth and nineteenth centuries, beavers remain sparse or missing from many stream reaches. Reasons for this failure have not been well studied. Our goal was to evaluate certain biotic factors that may limit the occurrence of dam‐building beavers in northern New Mexico, including competitors and availability of summer and winter forage. We compared these factors at primary active dams and at control sites located in stream reaches that were physically suitable for dam‐building beavers but where none occurred. Beaver dams mostly occurred at sites that were not grazed or where there was some alternative grazing management, but were mostly absent at sites within Forest Service cattle allotments. Results indicated that cattle grazing influenced the relation between vegetation variables and beaver presence. The availability of willows (Salix spp.) was the most important plant variable for the presence of beaver dams. We conclude that grazing by cattle as currently practiced on Forest Service allotments disrupts the beaver‐willow mutualism, rendering stream reaches unsuitable for dam‐building beavers. We recommend that beaver restoration will require changes to current livestock management practices.     

Bats of Lithuania: distribution, status and protection

The Lithuanian bat fauna includes 14 species. Myotis daubentoni, Pipistrellus nathusii, Plecotus auritus and Eptesicus serotinus are the most abundant and widespread species, although recently P. auritus has disappeared from some hibernacula. There are still abundant populations of Myotis nattereri, Myotis brandti and Barbastella barbastellus in hibernacula, while their status in summer is unknown. Myotis dasycneme is probably very rare and endangered. The status of Myotis mystacinus and Nyctalus leisleri is not clear, but they are most likely very rare because very few specimens have been found. So far little is known about status of Nyctalus noctula, Pipistrellus pipistrellus, Eptesicus nilssoni and Vespertilio murinus because these species are common only during autumn bat migration along the Baltic Sea coast. Two other species, Myotis bechsteini and Rhinolophus hipposideros, have been rejected from the list of bats of Lithuania, because old references to records of these species were not reliable. From what is currently known it seems that: (i) the northern limits of distribution of B. barbastellus and E. serotinus reach the middle of Lithuania between 55°N and 56°N, which may also be the southern limit of abundance of E. nilssoni; (ii) the wintering site with the largest numbers of bats in Lithuania is the vaults of Kaunas fortress, where every year eight species are found hibernating in numbers estimated as follows: M. daubentoni 400–500, M. nattereri 200–300, M. brandti 80–100, B.barbastellus 200–300, P. auritus 40–60, M. dasycneme 15–20 and a few E. serotinus and E. nilssoni. In Lithuania nine bat species have been protected by law since 1991, as species included in the Red Data Book. Also 11 bat reserves have been designated in Kaunas fortress to protect the most important hibernation sites in Lithuania.     

Predictive Occurrence Models for Bat Species in California

Abstract: The ability to accurately predict the potential occurrence of species of management concern is useful for wildlife managers, particularly for those whose management activities involve large areas where sampling is difficult due to logistical or financial constraints. During the summers of 2002 and 2003, we used mist nets to capture bats (Myotis yumanensis, M. californicus, M. evotis, M. thysanodes, Eptesicus fuscus, Lasionycteris noctivagans, Tadarida brasiliensis, Antrozous pallidus, Lasiurus borealis, and Lasiurus cinereus) in Whiskeytown National Recreation Area in north-central California, USA. We used landscape-scale variables, logistic regression, and Akaike's Information Criterion (AIC_c) to model species distributions and produce spatially discerning predictive occurrence maps. We developed a priori models that we used to determine which landscape-scale variables best discriminated between capture sites and non-capture sites. The odds of capturing a bat were 3.3 greater when total edge increased by 10,000 m, whereas for Yuma myotis (Myotis yumanensis), the odds of predicting presence were 0.2 greater when distance to lakes and ponds decreased by 2,000 m. Elevation was important in predicting the distribution of silver-haired bats (Lasionycteris noctivagans) and big brown bats (Eptesicus fuscus). Increasing elevation by 400 m decreased the odds of capturing a silver-haired bat by 0.1 and a big brown bat by 0.4. Classification accuracy for our models ranged from 80.9% for all bat species combined to 72.3% for Yuma myotis and silver-haired bats. Predictive occurrence models can be valuable to bat conservation efforts because they provide spatial data important for evaluating the effects of management activities on species distributions.     

Urban bat communities are affected by wetland size,quality, and pollution levels

Wetlands support unique biota and provide important ecosystem services. These services are highly threatened due to the rate of loss and relative rarity of wetlands in most landscapes, an issue that is exacerbated in highly modified urban environments. Despite this, critical ecological knowledge is currently lacking for many wetland‐dependent taxa, such as insectivorous bats, which can persist in urban areas if their habitats are managed appropriately. Here, we use a novel paired landscape approach to investigate the role of wetlands in urban bat conservation and examine local and landscape factors driving bat species richness and activity. We acoustically monitored bat activity at 58 urban wetlands and 35 nonwetland sites (ecologically similar sites without free‐standing water) in the greater Melbourne area, southeastern Australia. We analyzed bat species richness and activity patterns using generalized linear mixed‐effects models. We found that the presence of water in urban Melbourne was an important driver of bat species richness and activity at a landscape scale. Increasing distance to bushland and increasing levels of heavy metal pollution within the waterbody also negatively influenced bat richness and individual species activity. Areas with high levels of artificial night light had reduced bat species richness, and reduced activity for all species except those adapted to urban areas, such as the White‐striped free‐tailed bat (Austronomus australis). Increased surrounding tree cover and wetland size had a positive effect on bat species richness. Our findings indicate that wetlands form critical habitats for insectivorous bats in urban environments. Large, unlit, and unpolluted wetlands flanked by high tree cover in close proximity to bushland contribute most to the richness of the bat community. Our findings clarify the role of wetlands for insectivorous bats in urban areas and will also allow for the preservation, construction, and management of wetlands that maximize conservation outcomes for urban bats and possibly other wetland‐dependent and nocturnal fauna.     

Beaver invasion alters terrestrial subsidies to subantarctic stream food webs

North American beavers (Castor canadensis) were introduced to Tierra del Fuego Island in 1946 for their fur, and have since spread across the archipelago and onto the South American mainland. We assessed the impact of invasive beavers on streams of these forested watersheds by quantifying the trophic basis of production (TBP) and consumptive organic matter flows of benthic macroinvertebrate assemblages. TBP was determined in two streams: clear- and black-water. Stable isotopes were used across four streams to further elucidate food web structure and dominant pathways. TBP and stable isotopes showed that terrestrially derived organic matter (amorphous detritus, leaves, and wood) supported a majority of secondary production in the benthic food webs at all sites (forested reaches, beaver ponds, and sections downstream of ponds with foraged riparian zones). The magnitude of these flows was enhanced in beaver-modified sites compared with forested habitats (4.0–5.3× increase g AFDM m⁻² year⁻¹ in pond habitats, 1.1–2.1× increase in downstream habitats). Diatoms were the only autochthonous resource identified in macroinvertebrate guts, but their contribution to secondary production was small. Consumptive flows mirrored trends in TBP (i.e., dominance of terrestrial sources and greater magnitude in beaver ponds). Collector–gatherer consumption of amorphous detrital material dominated food web flows in all habitats, but was higher in beaver ponds relative to other habitats. Food web structure was simplified in beaver ponds; only two of the five possible functional groups contributed >1% of total organic matter flow in ponds (collector–gatherers and predators). Consumptive flows to predators increased in ponds, and stable isotopes of nitrogen and carbon (δ¹⁵N and δ¹³C) corroborated a relatively greater importance of predators (greater trophic distance), as well as less diversity of basal resources (less variation in δ¹³C) in ponds. Our findings indicate that invasive beaver’s engineering activities resulted in greater flows of terrestrial organic matter subsidies to in-stream food webs, which had a relatively greater change in the clear-water than in the black-water stream. Owing to the fact that these streams were naturally dependent on allochthonous resources for a majority of production and material flows, changes wrought by beavers to streams in forested environments are probably less than in watersheds with inherently greater dependence on autochthonous production such as the adjacent steppe biome.     

Beavers (Castor canadensis) facilitate early access by Canada geese (Branta canadensis) to nesting habitat and areas of open water in Canada's boreal wetlands

Several studies demonstrate how beavers influence waterfowl habitat availability, ultimately improving waterfowl breeding success; however, no current research links beavers to early season nesting activities of Canada geese (Branta canadensis) in northern climates. We examined how beavers facilitate early access to open water for geese at Miquelon Lake Provincial Park (MLPP), Canada. We surveyed 32 active and 39 inactive beaver ponds to examine whether beavers facilitate early access to open water. Open water occurred 10.7 days earlier at active beaver ponds (mean ice-off day = 87.54, s = 13.88) than inactive ponds (mean ice-off day = 98.19, s = 9.07), especially adjacent to main lodge entrances and winter food caches. Snowpack was on average 5.9 cm shallower at active ponds. Prior to availability of open water, Canada geese exhibited intraspecific territoriality over beaver lodges as nest sites and once water was present, preferred island lodges over bank lodges. These findings support other studies that examined island nesting as protection from terrestrial predators and highlight the importance of beavers in creating open water areas earlier in the season.     

Within‐season changes in habitat use of forest‐dwelling boreal bats

Bats utilize forests as roosting sites and feeding areas. However, it has not been documented how bats utilize these habitats in the boreal zone with methods afforded by recent technological advances. Forest structure and management practices can create a variety of three‐dimensional habitats for organisms capable of flight, such as bats. Here, we study the presence of boreal bats in a forest forming a mosaic of different age classes, dominant tree species, canopy cover, soil fertility, and other environmental variables, throughout their active season in the summer using passive ultrasound detectors. Our results indicate a preference for mature forest by Eptesicus nilssonii and a pooled set of Myotis bats. Both groups of bats also showed temporal changes in their habitat use regarding forest age. In June and July, both groups occurred more often in mature than young forests, but from August onwards, the difference in occurrence became less evident in Myotis and disappeared completely in E. nilssonii. In addition, E. nilssonii was more often present in forests with low canopy cover, and its occurrence shifted from coniferous forests to deciduous forests during the season. The results reflect the within‐season dynamics of bat communities and their ability to utilize different types of forest as environmental conditions change. Yet, the results most importantly emphasize the importance of mature forests to bat diversity and the need to conserve such environments in the boreal zone.