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Within-lodge interactions between two ecosystem engineers, beavers (Castor canadensis) and muskrats (Ondatra zibethicus)

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Within-lodge interactions between two ecosystem engineers, beavers (Castor canadensis) and muskrats (Ondatra zibethicus)

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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.

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... 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). ...
Article
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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.
... 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]). ...
Article
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). ...
Article
• 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). ...
Chapter
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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. ...
Article
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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.
... 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). ...
... 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 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 may serve as an important indicator species for changes in wetland ecosystems (Weller 1981(Weller , 1988Straka et al. 2018). ...
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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 lake connectivity, as well as 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
... 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. ...
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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
Article
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.
Article
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.
Article
Seasonal variation in food of the beaver (Caster canadensis Kuhl) was examined on the Mackenzie Delta, Northwest Territories, Canada. Leaves and, to a lesser extent, growing tips of willow (Salix spp.) were the main food items during July and August; during the remaining 10 months food consisted of the bark of willow (76%), poplar (Populus balsamifera) (14%) and alder (Alnus crispa) (10%). Protein: calorie ratios in the diet were approximately 40 and 8 mg/cal during those two periods respectively. The northern beaver has adapted to low energy availability characteristic of winter by storing food in the autumn and again in the spring, and by intrinsically lowering food intake during the winter. It has adapted to seasonal variation in protein availability by utilizing high-protein willow leaves almost exclusively when they are available. The heavy dependence upon willow, and its resultant removal from the community, can impart a high degree of instability to northern beaver populations.
Article
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.
Article
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.
Article
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
Article
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.
Article
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.
Article
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.
Article
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.
Article
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
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.