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Within-lodge interactions between two ecosystem engineers, beavers (Castor canadensis) and muskrats (Ondatra zibethicus)
Abstract
Ecosystem engineers are frequently observed to increase local biodiversity through their effects on resource flows. While promotion of successional processes and increased biodiversity may occur without direct interaction between ecosystem engineers and sympatric species, many cases exist where interactions are common. Under such conditions, it is unclear whether direct interactions serve to facilitate or inhibit coexistence of ecosystem engineers and the species attempting to use engineered habitats. We used remote videography within lodges of an ecosystem engineer, beavers (Castor canadensis), to quantify the taxonomic diversity of lodge use by non-beaver fauna and to characterize interactions between beavers and a second engineering species that commonly uses beaver-manipulated habitats, muskrats (Ondatra zibethicus). Beaver lodges were used by eleven types of vertebrates and invertebrates. Although no increased aggression was displayed by resident beavers towards intruding muskrats, the temporally partitioned patterns of muskrats' and beavers' entrances and exits to and from lodges, respectively, and altered behavior among both species during cohabitation, indicates that lodge use by muskrats represents an exploitative behavior as opposed to a mutualistic or even commensalistic relationship. We hypothesize that the ecological similarities between these species promotes competitive interactions, and the observed relationship highlights the tradeoffs faced by ecosystem engineers wherein constructed objects intended to exclude competitors are simultaneously associated with habitat modifications that promote the persistence of those same competitors.
... However, beavers may also construct bank lodges and excavate bank dens utilising overhanging ledges or tree roots to form non-island lodges (Fustec et al. 2003). The exterior and interior of beaver lodges are unique microhabitats, influencing both the aquatic and terrestrial surroundings (Mott et al. 2013). In some cases, beaver lodges are considered notably long-term structures within the community, potentially lasting more than 10 years (Müller-Schwarze 2011). ...
... North American otters (Lontra canadensis) were described interacting with beaver lodges in eight articles, the most published articles of any species. The articles documented North American otters using beaver lodges as natal sites (Gorman et al. 2006), under-ice access between ponds (Reid et al. 1988(Reid et al. , 1994, and areas for grooming and sleeping (Swimley et al. 1999, Mott et al. 2013, Tye et al. 2021). All North American otter behaviours were recorded in abandoned beaver lodges or in lodges where the beavers were absent. ...
... Muskrats (Ondatra zibethecus) were the second most cited species with seven articles. Mott et al. (2013) observed muskrats within 10 lodges out of 28 on 60 occasions, occupying lodges more frequently than any recorded species besides beavers. The beavers and muskrats showed temporally partitioned patterns when entering and exiting the lodges and changes in behaviour during cohabitation (Mott et al. 2013). ...
The positive relationship between biodiversity and beaver‐modified habitats such as ponds, dams, and canals has been demonstrated; however, the association between biodiversity and beaver lodges is rarely investigated. Due to increasing habitat fragmentation, there is a growing need to identify local biodiversity hotspots.
This systematic review assessed current scientific knowledge concerning the association between beaver lodges and biodiversity. Specifically, the study aimed to 1) investigate the evidence for beaver lodges being local biodiversity hotspots; 2) identify areas of future research centred around the relationship between biodiversity and beaver lodges; and 3) provide recommendations on how to monitor the relationship between biodiversity and beaver lodges within the UK.
Through a stepwise process of database searching and literature sorting, a final dataset of 35 articles emerged, with each article including at least one species, besides beavers, interacting with beaver lodges.
Analysis of the final dataset of articles showed beaver lodges offer multiple uses and fitness benefits for several species in highly seasonal environments, with daily and seasonal visitor variation influenced by intraspecific and interspecific interactions. Beaver lodges were shown to have higher species richness and diversity compared to microhabitats in the surrounding areas, supporting the concept of beaver lodges being local biodiversity hotspots.
We recommend that future studies use videographic methodology to monitor beaver lodges and other treatment groups in the surrounding area. Using the described methodology, beaver management plans should monitor beaver lodges across the northern hemisphere, helping to further understand these important local biodiversity hotspots.
... Beaver-induced flooding often leads to tree dieback and a consequent greater abundance of deadwood resources in the vicinity of a pond (Thompson et al., 2016). In addition, beaver lodges and burrows are microhabitats providing shelter or thermal refuges for other species (Mott et al., 2013;Stephenson, 1969). As a result, beaver activity increases the heterogeneity of niches, habitats and the landscape, positively influencing biodiversity (Law et al., 2019;Wright et al., 2003). ...
... The mosaic of heterogeneous habitats at beaver sites may constitute a refuge within the landscape that provides food, water and shelter. In beaver-modified habitats, therefore, the concentration of resources that are used by a diverse assemblage of species can reinforce interactions between organisms at various levels of the food web (Mott et al., 2013). ...
... We did not find a greater occurrence or activity of small herbivores on beaver sites, but this may have been due to the subnivean activity of rodents, which reduces their detectability on the snow surface (Korslund and Steen, 2006). Beaver sites facilitate the occurrence of small carnivores like weasels and polecats, which can use structures made by beavers, such as lodges, to shelter from larger carnivores (Mott et al., 2013). Previous studies reported that beaver ponds and shelters were also suitable foraging and denning sites for semi-aquatic predatory mammals like otters and minks (Mott et al., 2013;Nummi et al., 2019). ...
There is increasing awareness of the ecosystem engineering services provided by recovering populations of Eurasian beaver. By modifying aquatic environments, this species has a significant, positive influence on biodiversity. Beaver activity affects not only aquatic ecosystems but also terrestrial habitats and organisms. Our study compares and evaluates the species richness and activity of terrestrial mammals in winter at beaver ponds (N = 65) and randomly-selected reference sites along nearby watercourses unmodified by beavers (N = 65) in Poland (central Europe). Mammal assemblages were investigated near pond/watercourse edges, and also at some distance from them. The species richness of mammal and numbers of their tracks were respectively 25% and 33% greater on the beaver than on the reference sites. The higher species richness on beaver sites extended to areas 40–60 m distant from ponds, devoid any signs of beaver activity. Twenty-three mammal species were recorded on beaver sites (mean species richness 3.8 ± 1.6 SD), and 20 on reference ones (3.0 ± 1.5 SD). The numbers of tracks of grey wolf, least weasel and European polecat were higher on beaver than reference sites. Mammal species richness and activity were related to the existence of beaver ponds, but were also correlated with the numbers of snags and coverage of grass, bramble and coniferous saplings in neighbouring terrestrial habitats. Large and small carnivores occurred more frequently and were more active on beaver sites. The frequencies of occurrence of mesocarnivores, mesoherbivores and small herbivores were correlated with habitat characteristics, regardless of whether beavers were present or not. Our results highlight the fact that both pond creation and the habitat changes resulting from the presence of beavers rearrange the occurrence and activity of the terrestrial mammal assemblage.
... The substantial difference in body size is present from birth (340-630 g in beavers, 20 g in muskrats; Jenkins and Busher,1979;Willner et al., 1980), and although both species exhibit shape and size differences in the skull, they also share important morphological traits in adults, such as broad and short braincase, rostrum comparatively broader than other rodents, nasals expanded in its anterior portion, expanded zygomatic arches, mastoid process laterally projected, globose tympanic bulla, upper tooth row projected ventrally respect to the zygomatic arch in lateral view, and external auditory meatus projected laterally (Figs. 1 and 2). Both species also share the habitat, as they are semi-aquatic mammalian herbivores, exhibiting considerable niche overlap (Higgins and Mitsch, 2001;Mott et al., 2013), and being frequently observed using lodges together (Mott et al., 2013). Besides, both sympatric species use vegetation as construction material for lodges (Jenkins and Busher, 1979;Willner et al., 1980). ...
... The substantial difference in body size is present from birth (340-630 g in beavers, 20 g in muskrats; Jenkins and Busher,1979;Willner et al., 1980), and although both species exhibit shape and size differences in the skull, they also share important morphological traits in adults, such as broad and short braincase, rostrum comparatively broader than other rodents, nasals expanded in its anterior portion, expanded zygomatic arches, mastoid process laterally projected, globose tympanic bulla, upper tooth row projected ventrally respect to the zygomatic arch in lateral view, and external auditory meatus projected laterally (Figs. 1 and 2). Both species also share the habitat, as they are semi-aquatic mammalian herbivores, exhibiting considerable niche overlap (Higgins and Mitsch, 2001;Mott et al., 2013), and being frequently observed using lodges together (Mott et al., 2013). Besides, both sympatric species use vegetation as construction material for lodges (Jenkins and Busher, 1979;Willner et al., 1980). ...
... We expected post-translocation movements to remain within or close to release sites given the relative impermeability of surrounding upland landscapes and fetch impacts present in open water habitats (Larreur et al. 2020). Muskrats in North America are sympatric with American beavers and will often use active or inactive beaver lodges (Leighton 1933, Rosell et al. 2005, Mott et al. 2013, Windels 2017. It is plausible that beaver lodges could provide muskrats refugia from predation or adverse weather, and use of beaver lodges while prospecting in unfamiliar landscapes may confer increased fitness benefits such as increased survival probabilities (Rosell et al. 2005). ...
... Beaver lodges likely serve as temporary refugia for muskrats during their prospecting periods and may provide stepping-stone resources during dispersal. Although muskrat use of beaver lodges is well documented (Leighton 1933, Rosell et al. 2005, Mott et al. 2013, Windels 2017, ours is the first study to reveal the fitness benefits conferred to indi- Table 2. Known-fate model selection results describing post-translocation weekly survival of muskrats Ondatra zibethicus (n = 65) in Voyageurs National Park, MN, USA, during summers 2018 and 2019. Models were ranked by differences in Akaike's information criterion corrected for small sample sizes (ΔAIC c ). w = model weight, K = number of parameters within the model, Deviance = −2log ([log e likelihood of the model] -[log e likelihood of the saturated model]). ...
Muskrats Ondatra zibethicus are semiaquatic herbivores experiencing long-term and widespread population declines across North America. Translocation may be a viable tool to bolster or reestablish local populations; however, subsequent effects of translocation on muskrats are unknown. We live-trapped and translocated radiomarked muskrats (n = 65) during the summers of 2018–2019 in Voyageurs National Park, MN, USA and assessed post-translocation effects on weekly survival probabilities and space-use patterns. We did not observe homing behavior, though individuals moved an average of 2.2 km (SE = 0.30 km) from release sites and established home ranges within ∼8 days (SE = 1.16 days) post-translocation. Weekly post-translocation survival probabilities (0.95, SE = 0.001) and average home-range sizes (2.52 ha, SE = 0.44 ha) were similar to other studies of non-translocated muskrats. Our most-supported known-fate survival model revealed muskrats using beaver Castor canadensis lodges had greater weekly survival probabilities. Additionally, weekly muskrat survival varied between years suggesting a positive response to a novel soft-release technique applied in 2019. Our study provides the first empirical assessment of translocation effects on muskrats and suggests translocation may be effective for establishing or enhancing local muskrat populations. Additionally, our study suggests beaver lodges may confer fitness benefits to sympatric muskrats particularly during dispersal.
... They are also an invasive species in Europe, South America, and Asia (Anderson et al. 2006, Xu et al. 2006. Various authors have suggested that muskrats are keystone species (Danell 1996, Nummi et al. 2006, Law 2014, Brunke et al. 2017 or ecosystem engineers (Toner et al. 2010, Mott et al. 2013, Bridgewater & Aricò 2016, Greenhorn et al. 2017. Terminology can have significant conservation implications (Fischer et al. 2015), so it is important to avoid imprecise or misleading jargon. ...
... Native predators can benefit from new sources of food (Tornberg & Haapala 2013); however, the facilitative affect that introduced muskrats have on invasive predators, such as American mink in South America, can disrupt local food chains (Crego et al. 2016). Muskrats and North American beavers are sympatric in their native ranges, and muskrats often use beaver lodges in favour of their own huts (Mott et al. 2013, Crego et al. 2016. Synergistic impacts of beavers and muskrats can be devastating where they are both invasive (Valenzuela et al. 2013). ...
• Muskrats Ondatra zibethicus are reported to have wide‐ranging effects on wetland habitats, sometimes earning them the labels ‘keystone species’ or ‘ecosystem engineers’.
• We conducted an extensive review of the scientific literature and evaluated evidence for muskrats as potential keystone species or ecosystem engineers, and more generally, their known impacts on wetland ecosystems.
• We identified 363 publications (peer‐reviewed articles, books, theses, and reports) regarding muskrats, 202 of which were in an ecological context. Only 6% (n = 13) of these explicitly considered muskrats as ecosystem engineers (n = 9) or keystone species (n = 4).
• Our review found that muskrat populations may have broad effects on both wetland flora and fauna. However, studies generally occurred over small spatiotemporal scales and used dissimilar methods and reporting, which limited our inference regarding muskrats’ influence on wetland ecosystems.
• Research explicitly identifying muskrats as ecosystem engineers or keystone species is limited, but published evidence suggests that muskrats may have an effect on plant species diversity and habitat heterogeneity, which in turn may influence other animal species. However, long‐term and experimental research is needed to uncover impacts that muskrats have on ecosystems.
... These are the American beaver (Castor canadensis), the muskrat (Ondatra zibethicus), and the American mink (Neovison vison). These three species that interact in their native range in North America (Viljugrein et al. 2001;Shier and Boyce 2009;Mott et al. 2013) have reassembled those native interactions in the non-native ecosystems of the CHBR (Fig. 14.1; Crego et al. 2016). In this chapter, we explore the reassemblage of these three North American species and potential ecological impacts on the ecosystems of the sub-Antarctic Magellanic ecoregion, which represents a unique example of biotic homogenization between two subpolar ecosystems. ...
... With their dam-and den-building activities, together with foraging, they can alter the hydrology, geomorphology, and chemistry of freshwater ecosystems, having large effects on plant and animal species composition, density, and distribution (Baker and Hill 2003;Rosell et al. 2005). There is one species that benefits from beaver behavior, the muskrat, which frequently occurs in habitat associated with beaver dams and dens (Mott et al. 2013). Muskrats are also known to affect invertebrate and plant abundance and nutrient flows of aquatic habitats (Connors et al. 2000;de Szalay and Cassidy 2001). ...
At the southern end of the Americas exist one of the last pristine ecosystems in the world, the sub-Antarctic Magellanic forests ecoregion, protected by the Cape Horn Biosphere Reserve (CHBR). Despite its remote location, the CHBR has been subject to the growing influences of globalization, a process that has driven cultural, biotic, and economic transformations in the region since the mid-twentieth century. One of the most important threats to these unique ecosystems is the increase of biological invasions. Motivated by the expanding fur industry that responded to the globalization process, American beavers (Castor canadensis), muskrats (Ondatra zibethicus), and American minks (Neovison vison) were introduced, independently, to the southern tip of South America. Research has shown that these three North American species have reassembled their native interactions to affect negatively the invaded ecosystems of the CHBR. Beavers affect river flow and native vegetation, changing forests into wetlands, creating suitable habitats for muskrats. Muskrats, in turn, are the main prey of inland mink populations. The latter has major impacts by preying opportunistically on the native biota, especially native birds and small rodents. In this chapter, we explore this multi-species invasive system as an example of biotic homogenization, in which the introduction of these species and their subsequent reassembling of their interactions, together with the ecosystem impacts, offer a novel example of complex processes of biotic homogenization involving both biological and sociocultural dimensions.
... Three out of the 12 documented non-native mammals in this region are considered the most invasive and harmful: the American beaver (Castor canadensis), the muskrat (Ondatra zibethicus), and the American mink (Neovison vison) (Anderson et al. 2006b). These three species, which naturally interact in their native range in North America and Canada (Viljugrein et al. 2001;Shier and Boyce 2009;Mott et al. 2013), create an assemblage that has a large impact on biodiversity (e.g. Schüttler et al. 2008Schüttler et al. , 2009 and the structure and function of Magellanic Sub-Antarctic ecosystems (e.g. ...
... Beaver ponds are frequently used in North America by muskrats (Mott et al. 2013); another species capable of altering invertebrate and plant abundance and nutrient flow in aquatic habitats (Connors et al. 2000;de Szalay and Cassidy 2001). Muskrats were introduced to Tierra del Fuego simultaneously with beavers (Jaksic et al. 2002;Deferrari 2007); however, there are no studies on their potential impact on stream banks and wetlands. ...
With ecosystems increasingly having co-occurring invasive species, it is becoming more important to understand invasive species interactions. At the southern end of the Americas, American beavers (Castor canadensis), muskrats (Ondatra zibethicus), and American mink (Neovison vison), were independently introduced. We used generalized linear models to investigate how muskrat presence related to beaver-modified habitats on Navarino Island, Chile. We also investigated the trophic interactions of the mink with muskrats and beavers by studying mink diet. Additionally, we proposed a conceptual species interaction framework involving these invasive species on the new terrestrial community. Our results indicated a positive association between muskrat presence and beaver-modified habitats. Model average coefficients indicated that muskrats preferred beaver-modified freshwater ecosystems, compared to not dammed naturally flowing streams. In addition, mammals and fish represented the main prey items for mink. Although fish were mink’s dominant prey in marine coastal habitats, muskrats represented >50 % of the biomass of mink diet in inland environments. We propose that beavers affect river flow and native vegetation, changing forests into wetlands with abundant grasses and rush vegetation. Thus, beavers facilitate the existence of muskrats, which in turn sustain inland mink populations. The latter have major impacts on the native biota, especially on native birds and small rodents. The facilitative interactions among beavers, muskrats, and mink that we explored in this study, together with other non-native species, suggest that an invasive meltdown process may exist; however further research is needed to confirm this hypothesis. Finally, we propose a community-level management to conserve the biological integrity of native ecosystems.
... (e) Root foraging at high water levels creates a shelf along the river or pond along river or pond edges (photo taken along the Rio Grande near Albuquerque, NM, the semi-arid climate at 1828 m elevation) [36]. (f) When water levels drop, beaver burrows are exposed and, when abandoned, serve as unique habitats for use by other species (photo taken along the Rio Grande near Albuquerque, NM, semi-arid climate at 1524 m feet elevation) [37,38]. (g) To access branches, beavers will fell large trees, altering the composition of surrounding vegetation over time (photo taken along the Rio Grande near Albuquerque, NM, semi-arid climate at 1524 m elevation) [34]. ...
Virtual field trips in zoogeomorphology can allow students to explore the dynamic influence of beaver activity within the landscape. Education theory-informed virtual learning experiences (VLEs) of zoogeomorphologic topics, such as ecosystem engineers, are still underdeveloped for natural science learning communities. Through dam-building activities, beavers significantly alter stream hydrology, sediment transport, and vegetation organization and structure, promoting landscape heterogeneity. To effectively communicate this complexity of landscape modification, we developed an immersive virtual reality (VR) environment using historical photographs and detailed field notes to visualize the temporal and spatial transformations caused by beaver activity. A design and development process (TECCUPD), a philosophical framework for physical geography (TREE-PG), and a planning tool (VRUI conceptual model) are used to guide VLE architecture. Collectively, this information serves as a virtual proxy of an abandoned beaver pond field site to support student evaluation of the influence of sediment trapping and flooding on vegetation patterns on the landscape. This virtual place-based, experiential narrative environment is a proxy to capture the complexity of beaver-modified landscapes through ecological and geomorphological interactions. The integration of immersive VR technologies and generative artificial intelligence (AI) in higher education with learning theories that guide VR application design and development is applied in virtual field trips to support pedagogical goals and improve learning outcomes. Finally, we use an evaluation scale (TIPS) to assess the fidelity of learning theory implementation in a virtual field trip. Virtual field experiences in zoogeomorphology, informed by theory and utilizing immersive landscapes and scientific educational tools, can help students discern the effects of beavers on stream hydrology and geomorphic processes, as well as their potential role in mitigating water insecurity in climate adaptation efforts.
... The abundance of aquatic invertebrates and emerging aquatic insects in beaver ponds provides a significant food resource for several terrestrial insectivorous vertebrates, including water shrews Neomys spp., skunks (Mephitidae), long-tailed tits Aegithalos caudatus, and other small birds (Müller-Schwartze 2011;Orazi et al. 2022;Rosell and Campbell-Palmer 2022;Fedyń et al. 2023). Furthermore, lodges and dams provided by beavers can be used by terrestrial species as perches, feeding sites, migratory stopover sites, nesting areas, or burrows (Mott et al. 2013;Samas and Ulevičius 2015;Nummi et al. 2019;Mori et al. 2022). Some birds also exploit the standing dead timber as feeding and resting sites (e.g., woodpeckers: Hilfiker 1991; Stringer and Gaywood 2016;Orazi et al. 2022). ...
Ecosystem engineers such as beavers play a key role in shaping their habitats by modifying their physical environment and providing resources for other species. Beavers alter their surroundings by building dams, lodges, and canals, ultimately transforming rivers into dynamic networks of ponds and wetlands that may enhance biodiversity, by benefiting both terrestrial and aquatic wildlife. Rivers and the surrounding vegetation cover such as gallery and riparian forests are key habitats to several taxa, including bats and small mammals, two species-rich and conservation-relevant groups of vertebrates. Riverine ecosystems provide foraging, shelter, and commuting opportunities to these mammals. Recent evidence from northern Europe and North America suggests positive impacts on bat populations by beaver activities, due to the increased abundance of aquatic insects in beaver-modified environments, whereas the effects upon small mammals are less known. We aimed at assessing the effects of recently released beavers upon conservation relevant bats and small mammals in a Mediterranean context by following a bioacoustics monitoring approach. We compared bat and hazel dormouse diversity and activity at sites with and without beaver activity along three rivers in central Italy. Acoustic surveys confirmed higher bat and hazel dormouse activity levels at “beaver” sites with respect to control ones, particularly in areas surrounded by higher forest cover. Beaver sites exhibited a more pronounced positive response in bat activity levels as the surrounding forest cover increased. We also report that acoustically-detected hazel dormouse responded positively to beaver presence. We thus showed that both bats and dormice appeared to benefit from the presence of beavers at the sampled sites. Our study sheds light the ecological importance of beavers in enhancing habitat diversity and promoting biodiversity across aquatic and terrestrial ecosystems, highlighting positive effects upon conservation relevant taxa.
... They are also highly valued by First Nations, providing food, clothing, and income (Brietzke, 2015;Straka et al., 2018) as well as spiritual connection (MacGregor, 2013). Furthermore, muskrats are considered ecosystem engineers (Higgins, Mitsch, 2000;Mott et al., 2013;Kua et al., 2020) and keystone species (Straka et al., 2018;Danell, 1996) as they disproportionately influence the wetlands they live in. Through herbivory of emergent vegetation and the construction of houses and bank dens, muskrats alter the landscape and provide unique habitats for many wetland species (Weller and Spatcher, 1965;Danell, 1977;Hewitt and Miyanishi, 1997;Kua et al., 2020;Baici et al., 2024). ...
... Muskrats (Ondatra zibethicus) are thought to be important in North American wetlands. Considered by many to be ecosystem engineers (Higgins and Mitsch 2001;Mott et al. 2013;Kua et al. 2020), muskrats engage in activities that alter the structure of wetlands, such as building houses, excavating bank dens, and clearing emergent vegetation (Boutin and Birkenholz 1987;Connors et al. 2000;Kua et al. 2020;Bomske and Ahlers 2021). These activities have been associated with many benefits to wetland animal habitats. ...
Wetlands in southern Ontario are at risk of degradation and alteration due to human activities. This is a concern because wetlands provide essential habitat for species from a range of taxa, such as birds and anurans (frogs and toads). One wetland-dwelling species whose decline may be linked to loss of wetland wildlife habitat is the muskrat (Ondatra zibethicus). The decline of muskrats may also be linked to declines of other species because muskrats engage in activities that could support taxa such as birds and anurans by increasing habitat heterogeneity. We investigated whether bird and anuran species richness is related to muskrat density or if it is better predicted by land cover variables that describe the wetland and surrounding area at 30 coastal wetlands on Lake Ontario. We estimated bird and anuran species richness using data from the Great Lakes Marsh Monitoring Program and the Great Lakes Coastal Wetland Monitoring Program, and muskrat density based on muskrat house counts. Our results suggest that muskrat activity did not predict richness of anurans or birds overall; however, it did predict richness for the subset of birds that nest in emergent aquatic vegetation. Our results indicate that muskrat abundance in emergent marshes may increase habitat quality for birds that nest in emergent vegetation but may not have a measurable effect on anuran diversity in these same wetlands.
... oeconomus, A. amphibius) (Pucek, 1984). It is already known that other medium-sized and large semi-aquatic mammals benefit from beaver constructions and beavercreated wetlands (Sidorovich et al., 1996;Mott et al., 2013;Nummi et al., 2019;Fedyń et al., 2022), thus one may expect a similar effect in small rodents and shrews belonging to the same guild. Their response was, however, a mixed one. ...
Ecosystem engineers, such as the Eurasian beaver, Castor fiber, transform habitats, thereby creating favourable conditions for other species and increasing biodiversity. Multiple studies have revealed that beaver ponds are valuable habitats for invertebrates and vertebrates, including other mammals, but the impact of watercourse damming on the fauna of small terrestrial rodents and shrews has not yet been documented. We tested the hypothesis that the presence of beaver dams and consequent flooding enrich the small mammal assemblage both quantitatively and qualitatively. We live-trapped small mammals at nine beaver-modified sites on 300-metre transects alongside dammed watercourses, starting from the dam through to the pond to the sections with unmodified lotic conditions. The abundance and species richness of trapped small mammals were highest near the dams and declined with distance. Additionally, five out of 12 trapped species significantly decreased their abundance with linear distance along the shoreline from the dam and none revealed the opposite trend. Four species were more abundant on plots subjected to beaver-related inundation (especially Sorex minutus and Micromys minutus), while none were present solely on uninundated plots. Among the semi-aquatic species, two water shrews benefited from beaver activity in different ways. Neomys milleri occurred only in flooded sections, while N. fodiens preferred unmodified sections, but was the most numerous species closer to the dams, as per known patterns of competitive displacement observed in Central Europe. An important factor affecting small mammals, the herbaceous layer cover, appeared to be interdependent with damming. We provide the first unequivocal evidence that the presence of beaver dams facilitate the abundance and diversity of small mammals, presumably due to increased food abundance, availability of shelter and habitat connectivity. Beaver-created wetlands may act as potential refuges for species most susceptible to the consequences of anthropogenic climate change.
... Muskrats (Ondatra zibethicus) are thought to be important in North American wetlands. Considered by many to be ecosystem engineers (Higgins and Mitsch 2001; Mott et al. 2013; Kua et al. 2020), muskrats engage in activities that alter the structure of wetlands, such as building houses, excavating bank dens, and clearing emergent vegetation (Boutin and Birkenholz 1987;Connors et al. 2000; Kua et al. 2020; Bomske and Ahlers 2021). These activities have been associated with many bene ts to wetland animal habitats. ...
Wetlands in southern Ontario are at risk of degradation and alteration due to human activities. This is a concern because wetlands provide essential habitat for species from a range of taxa, such as birds and anurans (frogs and toads). One wetland-dwelling species whose decline may be linked to loss of wetland wildlife habitat is the muskrat ( Ondatra zibethicus ). The decline of muskrats may also be linked to declines of other species because muskrats engage in activities that could support taxa such as birds and anurans by increasing habitat heterogeneity. We investigated whether bird and anuran species richness is related to muskrat density or if it is better predicted by land cover variables that describe the wetland and surrounding area at 30 coastal wetlands on Lake Ontario. We estimated bird and anuran species richness using data from the Great Lakes Marsh Monitoring Program and the Great Lakes Coastal Wetland Monitoring Program, and muskrat density based on muskrat house counts. Our results suggest that muskrat activity did not predict richness of anurans or birds overall; however, it did predict richness for the subset of birds that nest in emergent aquatic vegetation. Our results indicate that muskrat abundance in emergent marshes may increase habitat quality for birds that nest in emergent vegetation but may not have a measurable effect on anuran diversity in these same wetlands.
... It seems clear that the small beaver deviates from the typical beaver construction plan simply because of its small body size (size of a muskrat), but also other physiognomic differences (no wide and flattened tail; different long-bone proportions) and thus is likely to represent a different ecology, possibly comparable to the extant muskrat -Ondatra zibethicus (Stefen and Rummel 2003;Daxner-Höck 2004). We know from present-day beavers that they can easily exist sympatrically in the same habitats with the muskrat, which is also semiaquatic (Mott et al. 2013). For a deeper palaeoecological analysis, in addition to dental investigations, profound functionalmorphological analyses of the entire skeleton must of course be carried out. ...
In this study, we describe the dental remains of a very minute beaver from the early Late Miocene locality Hammerschmiede (MN 7/8) located at the Northern Alpine Foreland Basin (Southern Germany, Bavaria). The finds represent the so far most comprehensive (>1.000 dental specimens) collection of the trogontheriine castorid Euroxenomys minutus. Metrically and morphologically, the large data set demonstrates an extensive intraspecific variability of this beaver from Hammerschmiede that covers most finds of other European localities and confirms previous species assignments. The subspecies Euroxenomys minutus rhenanus from Dorn-Dürkheim (Germany), clearly isolates from this range of variation and can thus be validated. The performed age-frequency distributions for Euroxenomys minutus from the local stratigraphic levels HAM 5 (rivulet) and HAM 4 (river) correspond roughly and also resemble Euroxenomys from the swamp deposit Rudabánya (Hungary). Since previous mortality studies on the also occurring larger beaver Steneofiber depereti from Hammerschmiede demonstrated dominance of behavioural or internal factors, this cross-ecosystem similarity in mortality for the small beaver species is likely explained by external factors, such as predation. Supported by a taphonomic bone analysis, a multitude of predators are finally considered to prey on Euroxenomys minutus and indicate a predatory bone assemblage.
... The specific feature of beaver activity is the building of relatively large structures, i.e., lodges and dams, that may act as both nexuses and corridors for the movements of other mammals. That applies especially to semiaquatic species, such as the muskrat Ondatra zibethicus or the American mink Neogale vison [18], which can use lodges as permanent shelters [19,20]. Research conducted in Belarus has shown that the European mink Mustela lutreola is strongly associated with beavers and uses both lodges and beaver ponds. ...
Simple Summary
To cross barriers in their habitats, animals often use specific corridors, and some of them may be created by other species, such as beavers (Castor canadensis and Castor fiber). Their dams on rivers may act as bridges for land mammals, but their importance is largely unknown. We investigated the function of beaver dams using tracking tunnels with kinetic sand to collect animal tracks. We assessed its suitability for this purpose since it has never been used as a tracking medium before. We placed those tunnels on dams, fallen trees (logs), and floating rafts and found that kinetic sand perfectly preserved the tracks of small carnivores, allowing easy identification, whereas shrews and rodents smaller than rats could only be detected but not recognised. The highest activity of mammals was observed on dams, as they may provide shelter, which allows safe travel and even residence. A slightly higher diversity was found on logs due to the visits of carnivores, which prefer leaving their scats in exposed places as markings. Our results reveal another function of the beaver as a creator of habitats for other animals and provide a novel tool for monitoring mammal activity.
Abstract
Physical obstacles within animal habitats create barriers to individual movements. To cross those barriers, specific corridors are used, some of them created by keystone species such as Eurasian beavers (Castor fiber). Their dams on rivers may also increase habitat connectivity for terrestrial mammals, but the significance of that function has never been quantified. To investigate this, we placed tracking tunnels on beaver dams, fallen trees, and—as a control—on floating rafts. Additionally, we tested kinetic sand as a novel substrate for collecting tracks and found the paws of small mustelids precisely imprinted in that medium, allowing easy identification. However, we needed to lump all shrews and rodents smaller than water voles (Arvicola amphibius) into one category as they can only be detected but not identified. The highest mammalian activity was observed on dams, as they may provide shelter, offering protection from predators during a river crossing or permanent residence, and even the opportunity to hunt invertebrates. Slightly higher diversity was found on logs because of a higher proportion of mustelids, which select exposed locations for scent marking. Our results increase our body of knowledge about the beaver as an ecosystem engineer and provide a novel tool for the monitoring of mammal activity.
... Ecosystem engineers tend to create unique habitats and microhabitats, otherwise absent in the environment, which opens up additional ecological niches by changing the amount and distribution of available resources in the area(Gutierrez et al. 2003;Law et al. 2017). In wetlands, the presence of ecosystem engineers can speed up ecological transitions and maintain environmental stability, creating intermediate levels of disturbance that enhance restoration efforts and ecological recovery(Curran and Cannatelli 2014;Law et al. 2017).In the wetlands of North America, the North American beaver (Castor canadensis) and the common muskrat (Ondatra zibethicus) are two notable ecosystem engineers(Higgins and Mitsch 2002;Mott et al. 2013;Curran and Cannatelli 2014;Rozhkova-Timina et al. 2018). Although the impact of C. canadensis has been well-observed and documented, the ecological impact of the common muskrat has received less attention, likely due in part to their adaptability to human and urban development(Cotner and Schooley 2011;Rozhkova-Timina et al. 2018). ...
... In the wetlands of North America, the North American beaver (Castor canadensis) and the common muskrat (Ondatra zibethicus) are two prominent mammalian ecosystem engineers (Higgins and Mitsch 2002, Mott et al. 2013, Curran and Cannatelli 2014, Rozhkova-Timina et al. 2018. A highly adaptable species, muskrats are relatively common throughout their native range in temperate North American wetlands, as well as in Europe and Asia where they are invasive and modify native ecosystems and human water control infrastructure (Cotner andSchooley 2011, Rozhkova-Timina et al. 2018). ...
Biotic ecosystem engineers are increasingly recognized as important drivers of biodiversity, structure, and function in many ecosystems. By regulating physical processes and creating local disturbances, ecosystem engineers can serve as important elements of passive habitat restoration, as they continuously alter and shape their environments. Native to North American temperate wetlands, the common muskrat (Ondatra zibethicus) is an ecosystem engineer that alters its environment through herbivory, house and structure building, and creation of activity networks. While the physical consequences of muskrat disturbances are well-known, few studies have quantified their impact on the wetland biotic community. We conducted a field study to investigate the effects of muskrat herbivory and structure building on plant biodiversity in wetlands along the upper St. Lawrence River (New York, USA) that have been extensively modified by long-term water regulation and non-native cattail invasion. Plant species richness and diversity were greater in muskrat-disturbed areas compared to at-large reference plots within the same wetlands.
Soil saturation mediated the biodiversity impacts of muskrats, with intermediate moisture levels resulting in the highest species richness. These interacting drivers, muskrat activity and hydrology, had a
compensatory effect on plant biodiversity loss associated with non-native cattail invasion. Multivariate analysis indicated a distinct plant community associated with muskrat disturbances. Analysis of spatiotemporal patterns of house locations suggests that some muskrats reuse house locations in sequential years, likely amplifying the intensity and duration of their impacts. This study demonstrates that muskrat disturbance influences wetland plant diversity at scales relevant to regional drivers of plant diversity.
... Muskrats are rodents with ecologically important roles in the food webs and communities of aquatic ecosystems; they are prey for numerous carnivores, primarily mink, eagles, and otter in the Mackenzie Delta, and can significantly impact the density and community composition of the plant foods they forage upon (Higgins and Mitsch 2001;Mott et al. 2013). Muskrat densities respond to lake water levels and they may serve as an important indicator species for changes in wetland ecosystems (Weller 1981(Weller , 1988Straka et al. 2018). ...
Climate change is altering Canada’s western Arctic, including hydrology in the heterogeneous environment of the Mackenzie Delta, and these changes are impacting biotic communities. Muskrats are culturally important semi-aquatic rodents whose populations may respond to changing water levels in this region. We investigated the importance of patch configuration and patch composition — two properties affected by climate change — on muskrat presence and distribution in the Mackenzie Delta, using remote sensing and field-based surveys of lakes with and without muskrats. We tested multiple hypotheses about predictors of muskrat and forage biomass presence using a model-selection approach. We found that configuration and patch composition explained muskrat distribution in the Mackenzie Delta, with composition being of greater importance. Muskrats were more likely to occur in lakes with longer perimeters, higher amounts of forage biomass, and sediment characteristics that supported macrophyte growth. The latter two conditions are related to spring flooding regimes, which will likely be altered by climate change. This may result in a decrease in muskrat habitat in the Mackenzie Delta. Our research indicates that both patch composition and configuration are important for understanding species distributions in heterogeneous environments.
... Muskrats often use beaver lodges for refuge (Mott et al. 2013, Rosell et al. 2005), but our observation clearly indicates they are vulnerable to predation when they take shelter within inactive lodges. While the inactive lodge from our observation had openings that allowed direct access to its interior, we suspect Fishers have the ability to tear apart old or rudimentary lodges to look for prey, as has been documented with other woody structures (Coulter 1966, Raine 1987. ...
Pekania pennanti (Fisher) is a generalist mesocarnivore that has been documented to prey on a diversity of mammals, but there have been no previous documented incidents of a Fisher hunting and killing a semi-aquatic mammal. Here, we report a first-hand observation and DNA evidence of a Fisher hunting and killing an Ondatra zibethicus (Muskrat) from inside a beaver lodge along a lakeshore.
... These interactions may affect species occupancy and detection. Despite use of similar habitats, there is no evidence of direct foraging competition between beaver and muskrat due to differences in feeding habits (Erb and Perry 2003); however, competition for space may occur (Mott et al. 2013). Mink (Neovison vison) are considered a primary predator of muskrat, and river otter (Lontra canadensis) may opportunistically prey on these small mammals (Errington 1943, Reid et al. 1994. ...
Streams and local riparian habitats are a product of the landscapes they drain. Consequently, aspects of the landscape, as well as local stream morphology, are likely to affect riparian and stream communities , including occupancy of semi-aquatic mammals. To gain a better understanding of how changing landscapes may affect the occupancy of semi-aquatic mammals, we sought to identify aspects of the riparian system and stream structure at multiple scales that relate to the presence of beaver (Castor canadensis) and muskrat (Ondatra zibethicus), including their interactions with mink (Neovison vison) and river otter (Lontra canadensis). We estimated multi-season occupancy using 103 sites sampled over six seasons (2012-2014) in southern Illinois, USA. We hypothesized beaver and muskrat occupancy was related to multiple aspects of landscape and local habitat including land-cover, water availability, human disturbance, stream characteristics, and the presence of other semi-aquatic mammals. Beaver occupancy varied over time and was predicted by stream size, stream density, and land-cover at the landscape scale. Muskrat occupancy also varied over time and was related to local aspects of habitat including percentage of forest in the riparian area, channel incision, land-cover, and aspects of sediment chemistry. Our results indicate the importance of spatial and temporal variation, scale, and food and water availability for these semi-aquatic species. Beaver and muskrat are most likely to be affected by changes to water regimes including availability of permanent water sources due to changing landscapes.
Muskrats are one of North America’s most widely distributed semi-aquatic mammals; however, populations are declining in many areas of North America yet expanding as an invasive species elsewhere. Its importance in native habitats and impacts in non-native environments warrants investigation into their habitat requirements. We compared the influence of several environmental factors to determine drivers of habitat selection. We hypothesized that distance to vegetation, vegetation type, distance to beaver lodges, beaver presence, and pond morphometry would influence muskrat habitat use. Through field surveys and GIS analyses, we used logistic regression and non-parametric approaches to assess various habitat metrics. Relative to randomly created points, muskrat huts were closer to adjacent vegetation, with more huts adjacent to cattail stands than other types of vegetation, although rushes (Juncus sp.) were most heavily browsed by muskrats. Although there were more huts and push-ups on occupied beaver ponds than on abandoned ponds, overall presence of muskrats did not differ. Push-ups exhibited random placement in ponds and weak associations with other variables, despite being adjacent to smaller vegetation stands with higher browse intensity than huts. Understanding habitat use allows unique insights into a species declining in native habitats yet creating ongoing challenges as an invasive species.
Freshwater habitats support high levels of biodiversity and provide important habitat for wetland‐dependent taxa; however, impairment of aquatic connectivity through wetland loss, stream alterations and light pollution impacts species persistence and community resilience. Quantifying occupancy of these habitats to assess their use by mammals and birds can be challenging, especially for cryptic species.
This study examines wetland habitat use by mammals and birds, and their spatial and temporal relationships within the Beaver Hills Biosphere in Alberta, Canada. As part of a multi‐method detection approach, camera boxes, cameras on beaver dams, and camera rafts allowed for multivariate analyses to determine temporal and spatial patterns of habitat use and species associations, while field sampling and environmental DNA (eDNA) provided data on site occupancy by a subset of semi‐aquatic mammals.
From ~50,000 images, over 84 species were detected, including 52 species of birds and 25 species of mammals. Several species were spatially associated, and although most species of mammals exhibited temporal overlap, there were distinct differences, especially on beaver dams where predators such as coyotes and white‐tailed deer shared the same space. Temporally, birds were detected most often during the day and mammals at night. During new moon phases, use of beaver dams by beavers decreased dramatically, and use of camera rafts by muskrats increased.
Winter field surveys allowed for a broad overview of wetland occupancy and abundance of some species, particularly by beavers and muskrats, and occasionally winter use by other semi‐aquatic mammals. Where there was limited detection of more cryptic species of semi‐aquatic mammals, eDNA analysis successfully detected American water shrew, American mink, North American river otter and northern bog lemming more often than camera and field methods.
Applying a multi‐method monitoring approach for mammals and birds in wetland habitats is critical at a time when freshwater systems are experiencing dramatic declines in relative abundance of monitored wildlife populations, with many of these species underrepresented in conventional surveys.
The Eurasian beaver (Castor fiber) was an important member of Early and Mid-Holocene landscapes and animal communities in Northern Europe. Previous zooarchaeological research has established the alimentary roles of beavers for Mesolithic societies and their importance for fur procurement. In this paper, we develop an integrated biocultural approach to human-beaver interactions, examining the position of humans and beavers in Mesolithic and Early Neolithic multispecies systems. We contextualize beaver landscape agency in hydroactive environments with human behaviour, synthesizing currently available data on mammalian assemblages, ichtyofauna and beaver-related material culture across Northern Europe. This cross-cultural, diachronic analysis reveals previously overlooked facilitations of human behaviour by beaver practices and ecological legacies. We show that long-term trajectories of human-beaver cohabitation differed between northern European regions. While in Southern Scandinavia, human-beaver intersections witnessed major re-organizations during the Mid-Holocene, beavers retained a key role for human societies across Northeastern Europe throughout much of the Holocene and played an important part at the Mesolithic-Neolithic transition in the Dutch wetlands. Divergent pathways are also evidenced by Mesolithic beaver-related material culture, highlighting the cultural keystone status of Castor fiber in higher latitude European landscapes. We argue that this keystone status is grounded in the supply of human hunting, fishing, and gathering affordances by the animals, pointing to the generative commensality between Mesolithic foragers and their beaver neighbours. Taken together, our findings demonstrate the importance of the beaver in the making of Early and Mid-Holocene forager societies in Northern Europe and illustrate the fruitfulness of deploying an integrated multispecies approach.
American beavers (Castor canadensis) are emblematic of diverse and dynamic freshwater ecosystems across North America. Numerous studies have described positive associations between beaver-modified habitats and biodiversity across a wide range of taxa. Yet few studies have documented biodiversity associated with the epicenter of beaver-modified habitats the beaver lodge. We used an internet-connected, solar-powered, time-lapse camera system to examine daily and seasonal temporal partitioning amongst vertebrate taxa that visited an American beaver lodge in south-central Nebraska over 9 mo. We observed at least 28 species on the lodge, and many organisms were present during discrete daily and seasonal time periods. These observations provide a more holistic view of a widely recognized, yet understudied, component of beaver-modified habitats. Future use of similar visual-recording systems may reveal that other animal structures, such as burrows, nests, and hives, are prominent ecosystem components in the wild.
Throughout midwestern North American ecosystems, semi-aquatic mammals including beaver ( Castor canadensis ), mink ( Neovision vision ), muskrat ( Ondatra zibethicus ), and river otter ( Lontra canadensis ) co-exist in wetlands. These species are ecologically important through their manipulation of habitats and interactions with other species present. Although natural resource managers in urban ecosystems are interested in semi-aquatic mammals and factors affecting their ecology, few such studies exist in the literature. We studied impacts of restoration practices and other environmental covariates on detection and occupancy of the 4 aforementioned focal species on forest preserves managed by the Lake County Forest Preserve District (Lake County, Illinois, USA). Sign surveys were conducted during December-April in 2018-19 and 2019-20. We quantified 12 variables representing bank measurements, temperature, precipitation, soil type, and survey replicate to inform the detection process and quantified 12 variables representing forest cover measurements, aquatic plant measurements, dominant landcover, restoration practices, and anthropogenic disturbances for the occupancy process. Single species, multi-season occupancy models were run in RStudio using the package unmarked . Detection probabilities ranged from 0.10 ± 0.07 for river otters to 0.60 ± 0.03 for muskrats; occupancy probabilities ranged from 0.28 ± 0.18 for river otters to 0.90 ± 0.05 for muskrats. Detection and occupancy were influenced by similar environmental factors (bank measurements, precipitation, and survey replicate for detection; and stream measurements and food availability for occupancy) compared to more rural locations. We provide further evidence that muskrats are urban adapters and document the initial stages of river otter recolonization in the Chicago Metropolitan Area.
Gray wolves are a premier example of how predators can transform ecosystems through trophic cascades. However , whether wolves change ecosystems as drastically as previously suggested has been increasingly questioned. We demonstrate how wolves alter wetland creation and recolonization by killing dispersing beavers. Beavers are ecosystem engineers that generate most wetland creation throughout boreal ecosystems. By studying beaver pond creation and recolonization patterns coupled with wolf predation on beavers, we determined that 84% of newly created and recolonized beaver ponds remained occupied until the fall, whereas 0% of newly created and recolonized ponds remained active after a wolf killed the dispersing beaver that colonized that pond. By affecting where and when beavers engineer ecosystems, wolves alter all of the ecological processes (e.g., water storage, nutrient cycling, and forest succession) that occur due to beaver-created impoundments. Our study demonstrates how predators have an outsized effect on ecosystems when they kill ecosystem engineers.
Global database of research into terrestrial animals with ecosystem engineering functions
Ecosystem engineers have been widely studied for terrestrial systems, but global trends in research encompassing the range of taxa and functions have not previously been synthesised.
We reviewed contemporary understanding of engineer fauna in terrestrial habitats and assessed the methods used to document patterns and processes, asking: (a) which species act as ecosystem engineers and with whom do they interact? (b) What are the impacts of ecosystem engineers in terrestrial habitats and how are they distributed? (c) What are the primary methods used to examine engineer effects and how have these developed over time? We considered the strengths, weaknesses and gaps in knowledge related to each of these questions and suggested a conceptual framework to delineate “significant impacts” of engineering interactions for all terrestrial animals.
We collected peer‐reviewed publications examining ecosystem engineer impacts and created a database of engineer species to assess experimental approaches and any additional covariates that influenced the magnitude of engineer impacts.
One hundred and twenty‐two species from 28 orders were identified as ecosystem engineers, performing five ecological functions. Burrowing mammals were the most researched group (27%). Half of all studies occurred in dry/arid habitats. Mensurative studies comparing sites with and without engineers (80%) were more common than manipulative studies (20%). These provided a broad framework for predicting engineer impacts upon abundance and species diversity. However, the roles of confounding factors, processes driving these patterns and the consequences of experimentally adjusting variables, such as engineer density, have been neglected. True spatial and temporal replication has also been limited, particularly for emerging studies of engineer reintroductions.
Climate change and habitat modification will challenge the roles that engineers play in regulating ecosystems, and these will become important avenues for future research. We recommend future studies include simulation of engineer effects and experimental manipulation of engineer densities to determine the potential for ecological cascades through trophic and engineering pathways due to functional decline. We also recommend improving knowledge of long‐term engineering effects and replication of engineer reintroductions across landscapes to better understand how large‐scale ecological gradients alter the magnitude of engineering impacts.
American beavers (Castor canadensis) forage on various aquatic and terrestrial plant species. We used stable isotope analysis of carbon (C) and nitrogen (N) to estimate source contributions of seasonal assimilated beaver diets in Voyageurs National Park, Minnesota, from Apr. 2007 to Nov. 2008. Mean (±95% confidence interval) annual beaver diets were estimated as 45.5 ± 11.4% terrestrial and 55.5% aquatic vegetation (22.0 ± 14.5 emergent and 33.5 ± 7.9 floating leaf). Percentages of floating leaf and terrestrial vegetation were similar between winter and summer assimilated diets, but emergent vegetation increased 45% in summer. Although δ15N was 7% greater in summer, δ15N and δ13C were similar by age class and sex, as were assimilated percentages of emergent, floating leaf or terrestrial vegetation. Variation in total assimilated aquatic vegetation did not affect subadult and adult seasonal changes in body mass, tail thickness or tail area, but kit body condition was negatively related to total assimilated aquatic vegetation. Aquatic vegetation accounted for more assimilated diet during winter than previously reported.
Guidelines for use of wild mammal species are updated from the American Society of Mammalogists (ASM) 2007 publication. These revised guidelines cover current professional techniques and regulations involving mammals used in research and teaching. They incorporate additional resources, summaries of procedures, and reporting requirements not contained in earlier publications. Included are details on marking, housing, trapping, and collecting mammals. It is recommended that institutional animal care and use committees (IACUCs), regulatory agencies, and investigators use these guidelines as a resource for protocols involving wild mammals. These guidelines were prepared and approved by the ASM, working with experienced professional veterinarians and IACUCs, whose collective expertise provides a broad and comprehensive understanding of the biology of nondomesticated mammals in their natural environments. The most current version of these guidelines and any subsequent modifications are available at the ASM Animal Care and Use Committee page of the ASM Web site (http://mammalsociety.org/committees/index.asp).
A field study of the coexisting, nocturnally active small mammals Sminthopsis crassicaudata and Mus musculus showed that both species occupied nests during the day in groups of up to nine individuals. In S. crassicaudata, nest-sharing was common in winter (up to 70% of individuals), but it declined during the breeding period of spring and summer; in M. musculus, nest-sharing remained common throughout the year. Some (about 30%) nest-sharing was interspecific. Diurnal torpor occurred in both species during the colder months, but in fewer than 10% of the individuals observed. Nest-sharing in S. crassicaudata is interpreted as a behavioral energy-conserving device to counter seasonal depression of temperature and food supply; torpor appears to be used only when foraging conditions are particularly poor. A similar explanation may apply to M. musculus.
Ecosystem engineers are organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials. In so doing they modify, maintain and create habitats. Autogenic engineers (e.g. corals, or trees) change the environment via their own physical structures (i.e. their living and dead tissues). Allogenic engineers (e.g. woodpeckers, beavers) change the environment by transforming living or non-living materials from one physical state to another, via mechanical or other means. The direct provision of resources to other species, in the form of living or dead tissues is not engineering. Organisms act as engineers when they modulate the supply of a resource or resources other than themselves. We recognise and define five types of engineering and provide examples. Humans are allogenic engineers par excellence, and also mimic the behaviour of autogenic engineers, for example by constructing glasshouses. We explore related concepts including the notions of extended phenotypes and keystone species. Some (but not all) products of ecosystem engineering are extended phenotypes. Many (perhaps most) impacts of keystone species include not only trophic effects, but also engineers and engineering. Engineers differ in their impacts. The biggest effects are attributable to species with large per capita impacts, living at high densities, over large areas for a long time, giving rise to structures that persist for millennia and that modulate many resource flows (e.g. mima mounds created by fossorial rodents). The ephemeral nests constructed by small, passerine birds lie at the opposite end of this continuum. We provide a tentative research agenda for an exploration of the phenomenon of organisms as ecosystem engineers, and suggest that all habitats on earth support, and are influenced by, ecosystem engineers.
House building sites consisted of open water areas and heavy emergent vegetation stands, particularly cattail Typha stands, with >15 cm water. Average home range had a ratio of vegetation:open water areas of 1:1. With a decline in water lvel, muskrats extended their home range significantly from 484 (+ or -238.4) m2 in June-July to 1112 (+ or -842.7) m2 in August-September and increased significantly the average number of houses/family from 1.5(+ or -0.7) in early summer to 3.9(+ or -1.7) in late summer. Cattail was the most important foodstuff but food habits depended upon the movements of the animals and the diversity of the flora. Adult and juvenile populations usually had an even sex ratio in summer. Most females had 2 litters with an average of 6.3 embryos/litter. In cattail-rich areas, females produced 1-4 more young/litter than females of other habitat types and there were more animals/ha of home range (>100 animals) than in any other habitat type (<80 animals). Survival rate of juveniles was estimated at 66.4% in summer and 31.8% in winter. Maximum life span was 5 yr.-from Authors
The creation of aquatic patches by Castor canadensis in the boreal forest of N Minnesota was studied to determine how the population dynamics of a disturbance-causing animal are linked to rates of patch formation and growth over a period of population expansion and stabilization. Using 6 series of aerial photographs taken between 1940-1986, the authors show that the rate of patch formation as much higher during the first 2 decades of colonization than during the subsequent 2 decades. Average area of all pond sites, which included both filled and drained ponds, remained at c4 ha throughout the period, but average area of new ponds decreased significantly over time. Ponds established by 1961 constituted 75% of the total number and 90% of the total pond-site area as of 1986. When pond sites of similar age but different pond cohort (decade of establishment) were compared, average area per pond site was always significantly larger for the earlier cohort. Rate of patch formation after the first two decades of beaver colonization was probably constrained by geomorphology, which limited the availability of sites at which a beaver dam could impound a large area of water. -from Authors
Conspecific nest parasitism is much more common in birds that have self-feeding young than in those with parentally fed young. We review evidence for this pattern and suggest that it is produced by a fundamental dichotomy in selection pressure for defense against conspecific parasites. Species that feed their young should experience intense selection pressure for effective defense against parasitism, because their reproductive output is limited by post-hatching parental care. Species that have self-feeding young, however, experience only mild selection for parental defense against parasites, because their reproductive output is constrained chiefly by their ability to produce eggs. For such birds, parental care can be shared with little or no detriment to survival of young. Within both the self-feeders and the birds that feed their young the occurrence and intensity of conspecific nest parasitism is dictated primarily by the ability of parasitic females to find host nests. This pattern is particularly clear among waterfowl, where conspecific nest parasitism is frequent in ducks that nest in cavities, over water, or in high densities on islands. We review evidence that suggests greater conspecific nest parasitism for parentally fed species that nest in colonies than parentally fed species with dispersed nests. We also make predictions about the distribution of conspecific nest parasitism in nonavian groups.
Basal metabolic rate (BMR), serum thyroxine (T4) concentration, lean organ mass, and body composition were measured in 94 captive, seasonally acclimatized muskrats (Ondatra zibethicus) between May 1991 and April 1992. Seasonal measurements of oxygen consumption, body water content, and mass were obtained from an additional 124 captive or free-ranging animals in 1994ñ1995. Mass-independent BMRs (kJ · kgñ0.67 · hñ1) and serum T4 concentrations (nmol · Lñ1) varied significantly over the year (P < 0.0001), with mean values in February exceeding July values by 31.1 and 77.2%, respectively. These variables tracked seasonal changes in the neutral detergent soluble (NDS) content of broadleaf cattails (Typha latifolia), the dominant food of muskrats in the study population. From July through February, alimentary tract, liver, spleen, and heart masses increased, while kidney mass declined. Body fat stores varied significantly over both years, with peak values measured in February. However, lean body and pelt masses exhibited little seasonal variation (P > 0.05). Stepwise multiple regression and principal component analyses suggested that variation in BMR was associated most closely with changes in heart and alimentary tract masses. Annual variations in basal energy expenditure, serum T4 concentration, and organ masses of wild muskrats appear to be linked to seasonal changes in forage NDS content and energy intake, and may be important factors relating to the annual pattern of fat accretion and mobilization in this semiaquatic rodent.
Drawdown management was used near Port Clinton, Ohio, to restore suitable Ondatra zibethicus habitat in one growing season; muskrats moved into the area immediately and reproduced at high rates, numbers of muskrat houses peaking in the 3rd year. Managers of restored marshes should initially emphasise moist soil and shallow flooding to encourage perennial plants. -from Authors
Beavers live in discrete family units consisting of an adult pair and progeny from 1 or more years. Activity is predominantly crepuscular and nocturnal, although winter activity rhythms may be free-running. One beaver, typically an adult, is usually first to initiate daily activity of the family. Many behaviors are seasonal. An overview of the annual cycle of events is presented. Burrow/lodge, dam, canal and channel, and food cache construction and/or maintenance behaviors are described. Females are more active in burrow/lodge initiation, pre-winter lodge maintenance, and dam construction and maintenance than males. Beavers use several communication systems, immediate and long-term, to maintain family integrity and to transmit interfamily information. Tail-slapping serves primarily as a warning signal to family members on land or in shallow water to move to deep water. Scent marking is important in labeling family habitat and conveys both inter-and intra-family information. Most vocalizations occur in social context. Kits are most vocal and use the whine call primarily to obtain woody food from older family members.-from Authors
Muskrat (Ondatra zibethicus) herbivory and lodge construction create open water areas in stands of emergent vegetation. This study examined how aquatic invertebrates are affected by changes in the physical structure of plant stands created by muskrats. We compared density, species composition and functional feeding groups of benthic macroinvertebrate communities and abiotic conditions in open water areas at muskrat lodges and in adjacent cattail stands. Although total numbers of macroinvertebrates were not affected by muskrat activities, communities at muskrat lodges were less diverse than in cattail stands. Gathering collectors such as chironomid midges that feed on fine particulate organic matter were the dominant trophic group; these were significantly more abundant at muskrat lodges than in cattail stands. Scrapers, such as gammarid scuds that feed on periphyton, were also abundant; these were significantly more abundant in cattail stands than at muskrat lodges. Water temperature, dissolved oxygen, pH, conductivity and sediment organic content were different in these habitats. These results indicate that muskrats alter 3abiotic conditions and invertebrate communities in wetlands, which will affect food resources for wildlife and fish that feed on aquatic invertebrates in these habitats.
Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).
By their nature nests and burrows can come to exert important influences upon certain habitats and a number of different ways in which they do this can be identified. These have implications for the understanding of social evolution, species diversity and habitat stability which deserve greater attention. -from Author
We examined the energy saving and social interactions associated with winter huddling behavior in the muskrat, Ondatra zibethicus. At air temperatures of −10°C and 0°C, which encompass the lowest microclimate temperatures recorded from winter shelters, the resting metabolic rate of an aggregate of four muskrats averaged 11-14% below that of single animals. The minimal thermal conductance of the grouped animals was reduced by 8-10% over this same temperature range. Our findings suggest that communal nesting confers a modest, but potentially significant metabolic saving to overwintering muskrats.
Microbial densities on plant litter from muskrat mounds and the surrounding marsh floor in a Michigan marsh were compared. Litter was sampled from mounds and the marsh floor nine times during 1 yr. Aerobic and anaerobic microbes were cultured from the litter samples using the plate count technique with four types of growth media. The density of microbes ranged widely depending on the type of growth medium and the presence or absence of oxygen. Litter from muskrat mounds supported significantly higher densities of microbes than litter from the marsh floor. We suggest that muskrat mounds act like the compost piles of organic gardeners in providing a microenvironment conducive to enhanced microbial growth and accelerated decomposition.
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.
Responses of a high muskrat (Ondatra zibethicus) population to a deteriorating habitat were studied at Goose Lake, a 135-acre central Iowa marsh, during 1961. Apart from certain "cyclic" implications in the situation, the most remarkable findings from this particular study relate to the indifferent breeding performance of the muskrats from spring to midsummer, followed by a late-breeding spurt in August and September after ear corn in fields adjacent to the marsh became utilized by the muskrats on an extensive scale. To summarize the differences in seasonal distribution of 88 litters born to or conceived by adult females at Goose Lake in 1961 and samples totaling 3,209 litters from Iowa study areas collectively, 1935-57. There were about three times the proportion of early-season litters in the long-term Iowa series as for Goose Lake in 1961, similar proportions of mid-season litters, and over four times the proportion of late-born litters in the 1961 Goose Lake sample as for the Iowa series.
All vegetation change can be reduced to one of three basic phenomena, succession, maturation, and fluctuation, or some combination of these. Each of these phenomena is a result of a change in some attribute of one or more of the plant populations comprising the vegetation of an area. Succession ocurs when different populations are present from time to time. Maturation is an increase in the biomass of an area which is the result of a change in the age/size structure of the populations with time. Fluctuations result from changes in the number of individuals or ramets in the populations of an area from year to year.
The contribution of succession, maturation, and fluctuation to the vegetation dynamics of Eagle Lake, a prairie glacial marsh in Iowa, is examined. In those areas where changing water levels and extensive musk-rat damage occur, succession is the most important phenomenon. A knowledge of the life-history characteristics of each species, particularly its establishment requirements, the presence or absence of its seeds in the seed bank, and its life-span, enables successional sequences to be predicted in this marsh. There are short periods where maturation is the major phenomenon causing vegetation change. Fluctuations also occur both in the emergent vegetation and the submerged vegetation.
In this study we attempt to correlate the seasonal behavior patterns with the physiological cycles, and suggest how they may affect the composition and density of the population in the Wisconsin marshes. The investigation includes anatomical data from 237 muskrats, from every month of the year, and field observations on seasonal behavior patterns. The number of animals examined was limited by the difficulty of obtaining them. Most of the muskrats were captured alive, while a few were freshly skinned carcasses obtained from trappers. The live muskrats were obtained from the Horicon Marsh Wildlife Area in
Foraging data collected for beaver (Castor canadensis) at Isle Royale National Park, Michigan, during the summer of 1973 provided basic natural history information pertaining to diet, food preferences, rates of consumption and activity cycle. Beaver foraging was consistent with a linear programming model of herbivore optimal foraging. The model was used to predict beaver diet, the maximum distance a beaver foraged from its pond, and the manner in which the minimum and maximum diameters of beaver-cut woody vegetation changed with distance from the pond.
Despite the ubiquity of denning as a natural history strategy among terrestrial vertebrates, little is known regarding basic patterns of within-den behavior, how such patterns are influenced by demographic and environmental parameters, or how within-den behavioral repertoires relate to activities performed in external environments. Den usage is believed to facilitate increased expression of behaviors that compromise fitness in external environments, though empirical data validating these assumptions are generally lacking. Relative isolation from external light cues within dens has been linked to temporal patterns of den use, yet few studies examine associations between photoperiod and rhythmicity strictly for within-den behavior. Also, for denning species with relatively equivalent parental investment, conclusions regarding sex-specific behavior have been equivocal, and no studies have examined potential segregation of parental activity within dens. We videorecorded 1506h of within-den activity from 23 beaver (Castor canadensis) colonies and characterized behavioral patterns based on sex and age over daily and monthly intervals. Within-den time-activity budgets were equivalent among male and female adult beavers, with feeding, sleeping, allogrooming, and individual grooming accounting for more than 95% of all recorded behaviors. Behavioral repertoires within dens exhibited distinct seasonality and were influenced by temporal variation in external conditions associated with food availability, indicating linkages between activities within and outside of dens. Lastly, beaver age classes varied considerably in their associations between diel activity patterns and photoperiod, with adults and kits exhibiting single and multiple sleep–wake cycles, respectively.
We investigated the space-use patterns of adult muskrats in a small (77 ha) marsh on the Canadian Prairies during two breeding seasons. During the study, population size was relatively low and the adult sex ratio was biased towards females. Adult muskrats were territorial with little intrasexual home-range overlap. The exclusivity of home ranges was maintained throughout the breeding season, and appeared to decrease at the end of the season. Male movements often extended over the territory of more than one female, but the overlap was more extensive with primary than with secondary females. Lactation appeared to reduce the space use and mobility of female muskrats. Male muskrats tended to range over smaller areas when weaned young were present within their home range. The results suggest that the sexual pair is the basic social unit of muskrats but that polygyny was common. A female-biased sex ratio appeared to be responsible for the tendency of males to mate polygynously during this study, thus illustrating the plasticity of this social system.
Comparative studies of how female and male North American beavers (Castor canadensis) allocate time provide a basis for understanding their life history. I studied the behavior of beavers living in lake habitats of a near-boreal region to determine how animals of each sex allocated time during their active periods. Markov time-budget estimates revealed that over the open-water season, adult females and males spent 91 and 86%, respectively, of time during active periods feeding, traveling, and being in the lodge. Adult females spent most of their time feeding in late spring and summer. In late summer through fall, they spent more time provisioning, working on lodges, and constructing winter food caches. In contrast, adult males spent less time feeding and more time traveling, being in the lodge, and working on the lodge in late spring and early summer. As the season progressed, adult males traveled less and spent more time feeding and working on the lodge. Overall, the results suggest that there is a division of labor in this monogamous species. Adult females seemed to function primarily as providers of energy to kits. In contrast, adult males seemed to function primarily in protection and provisioning of kits, territory maintenance, and construction and maintenance of structures.
A common perception is that desert birds experience greater extremes of heat and aridity than their mammalian counterparts, in part, because birds do not use burrows as a refuge from the desert envi- ronment. We report observations of Dunn's Larks (Er- emalauda dunni), Bar-tailed Desert Larks (Ammo- manes cincturus), Black-crowned Finch Larks (Ere- mopterix nigriceps), and Hoopoe Larks (Alaemon alaudipes) using burrows of the large herbivorous liz- ard Uromastyx aegypticus as thermal refugia during hot summer days in the Arabian Desert. Continuous recordings of shade air temperature (T,), soil surface temperature (T,,,,), burrow air temperature (Ta_burrow), and burrow substrate temperature (TsubsVate) showed that T surface exceeded 60°C on most days. T, typically ex- ceeded 45°C whereas Ta_burrow was around 41°C during midday. Calculations of total evaporative water loss at different temperatures indicated that Hoopoe Larks can potentially reduce their water loss by as much as 81% by sheltering in Uromastyx burrows during the hottest periods of the summer day.
Sibling and neighbour recognition were examined using wild-caught juvenile muskrats, Ondatra zibethicus, of known sibship in dyadic encounters. Behavioural asymmetry between sibling and nonsibling dyads indicated the presence of sibling recognition. Recognition of neighbours was examined using indices of agonistic and amicable behaviour calculated using exclusively non-sibling dyads. The distance between captures within non-sibling dyads was used to approximate familiarity. Amicable behaviour decreased significantly with increasing distance between captures, and, therefore, with decreasing familiarity. Agonistic behaviour was not correlated with distance between captures.
The littoral zones of many boreal headwater lakes in northwestern Ontario are composed of rocks, boulders, and sand, with sparse macrophyte growth. This study investigated the possibility that abandoned beaver lodges might structure littoral communities in these systems through providing accumulations of coarse woody debris and entrapped sediment. The richness and abundance of 10 benthic macroinvertebrate taxa, 6 species of small fishes, and 2 species of amphibians were found to be significantly elevated near beaver lodges compared with areas of sand and rocks otherwise characteristic of the littoral zones in these lakes. Beaver in Ontario are generally regarded as a nuisance or a resource; wildlife managers therefore encourage extensive trapping before large populations can become established. The results of this study suggest that beaver provide an important habitat resource for littoral communities in boreal headwater lakes. As a result, endorsement of limiting beaver populations through increased trapping should be reexamined for regions containing macrophyte-impoverished lakes with a rocky shore.
We studied the differential use of lodges and burrows by muskrats in a large (293 ha) northern marsh, during a period characterized by a 100-fold variation in apparent density. Population size (as indexed by dwelling numbers), summer heat stress, rate of collapse of lodges, and over-winter occupancy of lodges and burrows were investigated as potential determinants of dwelling selection. Muskrats selected against lodges at low population size, even when water level was experimentally controlled within a normal range. Sun-exposed lodges in summer were not subject to extreme internal temperatures capable of impairing the survival of young muskrats confined to nests. Lodges were dynamic structures that required substantial and continual upgrade during the ice-free season. Lodges also had a lower probability of remaining active through the winter compared with burrows, possibly because of the freezing of surroundings. We suggest that higher maintenance cost and greater vulnerability to predators likely constitute two critical determinants for muskrat selection against lodges at low population size.
The winter bioenergetics of a beaver population were studied in au area of Wood Buffalo National Park; which is located partly in Alberta and partly in the Northwest Territories. In these latitudes the beaver (Castor canadensis canadensis) are confined to subnivean existence for approximately 150 days each year. Although there is an unlimited supply of deciduous trees, which are cached by the colonies for this period, the caches were not sufficient for the energy requirements of the colonies, as calculated from the number and weight of animals in each colony. This indicates that energy deficits are a product of the winter behavior of the animals and that methods of energy conservation, such as reduced activity, periods of dormancy, huddling, insulation from ambient temperatures by lodge construction, and an increase in fur insulation and fat deposition provide the necessary mechanisms for survival. Based on a comparison of autumn and winter weights of beaver, the younger animals (kits and yearlings) increased their weight during the winter while the older animals, who presumably use fat reserves for survival, did not.
The Eurasian beaver, Castor fiber, is one of the few obligate monogamous mammal species known, and nothing is known about the time budget of the mated pair. We investigated whether mated adult Eurasian beavers would display sex differences in time budgets. Using radiotracking, we obtained behavioural data on six mated pairs of adult beaver during 2000 and 2001 on two rivers in southeast Norway. Time budgets for males and females were compared in total and over the seasons, along with temperature data collected throughout the study. The three main behaviours of both males and females were travelling, foraging and being in the lodge, accounting for 92.0 and 93.2%, respectively, of each sex's overall time budgets. Time budgets did not differ between the sexes except that males allocated more time to travel. Time budgets for each sex did not vary with season, and water and air temperature data were positively correlated with time spent travelling for both sexes. These results support the hypothesis that male and female time budgets are similar, except for the time that males and females allocated to travel. We suggest that the similarities in behaviour result because parental care by both parents is essential to the successful rearing of offspring, leading to reduced behavioural sexual dimorphism; nevertheless, some differences still occur, perhaps relating to the male's indirect parental care. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.