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Karen E. Hodges - One of the best experts on this subject based on the ideXlab platform.
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Post-fire salvage logging reduces Snowshoe Hare and red squirrel densities in early seral stages
Forest Ecology and Management, 2020Co-Authors: Angelina J. Kelly, Karen E. HodgesAbstract:Abstract Wildfire is an important natural disturbance in western North American forests and has been increasing in prevalence and severity in recent decades. Post-fire salvage logging is a common practice, however, the impacts of salvage logging on wildlife are poorly understood. We studied populations of Snowshoe Hares (Lepus americanus) and red squirrels (Tamiasciurus hudsonicus) in a post-fire and salvage-logged interior Douglas fir (Pseudotsuga menziesii) forest on the Chilcotin Plateau, British Columbia, Canada. Snowshoe Hare densities were low, but densities were highest in 8–9-year-old regenerating post-fire forests. Hares were mostly absent from 1 to 2-year-old post-fire forests. Salvage-logged areas were not used by Snowshoe Hares. Red squirrel detections were highest in mature forests, and squirrels were not present in post-fire salvage-logged habitat. Post-fire salvage logging removed live canopy trees required by both Snowshoe Hares and red squirrels. The large scale and intensity of post-fire salvage logging removes important regenerating post-fire habitat and has detrimental impacts on these important prey species, likely leading to consequences for avian and mammalian predators.
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Impact of wildfire size on Snowshoe Hare relative abundance in southern British Columbia, Canada
Fire Ecology, 2019Co-Authors: Jenna Hutchen, Karen E. HodgesAbstract:Large wildfires result in more heterogeneous fire scars than do smaller fires because of differences in landscape context and high variability in burn intensity and severity. Previous research on mammal response to wildfire has often considered all fires as comparable disturbances regardless of size. Here, we explicitly examine whether fire size affects relative abundances of a keystone herbivore, Snowshoe Hare (Lepus americanus Erxleben, 1777), in regenerating stands of the same age. We surveyed vegetation and fecal pellets of Snowshoe Hares in nine 13-year-old wildfires, specifically, three fires in three size categories—small (80 to 200 ha), medium (1000 to 5000 ha), and large (>10 000 ha)—and in mature forests in southern British Columbia, Canada. Snowshoe Hare density was low (0.4 Hares ha−1), but Hares were present at 57% of mature sites. Hares were absent from all areas where small fires had burned and were found in only one medium area post fire (0.2 Hares ha−1). Hares were found within the fire scars of all three large burned areas, and with much higher numbers (3.8 Hares ha−1) than in the medium fire area or mature forest. Snowshoe Hare abundance was highly correlated with the number of sapling trees, especially lodgepole pine (Pinus contorta Douglas ex Loudon). Sapling densities were highly variable, but dense stands of saplings were found only in burn scars from large wildfires. Fire size is an important predictor of Snowshoe Hare relative abundance in areas that are regenerating post fire; fires of different sizes are not comparable disturbances. Specifically, the post-fire heterogeneity after large fires enabled both the highest Hare numbers as well as patches with no Hares. These results suggest that forest and wildlife managers should protect areas with dense regeneration post fire, as these sites are necessary for Hares after large wildfires.
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Conservation implications of the evolutionary history and genetic diversity hotspots of the Snowshoe Hare
Molecular ecology, 2014Co-Authors: Ellen Cheng, Karen E. Hodges, José Melo-ferreira, Paulo C. Alves, L. Scott MillsAbstract:With climate warming, the ranges of many boreal species are expected to shift northward and to fragment in southern peripheral ranges. To understand the conservation implications of losing southern populations, we examined range-wide genetic diversity of the Snowshoe Hare (Lepus americanus), an important prey species that drives boreal ecosystem dynamics. We analysed microsatellite (8 loci) and mitochondrial DNA sequence (cytochrome b and control region) variation in almost 1000 Snowshoe Hares. A hierarchical structure analysis of the microsatellite data suggests initial subdivision in two groups, Boreal and southwestern. The southwestern group further splits into Greater Pacific Northwest and U.S. Rockies. The genealogical information retrieved from mtDNA is congruent with the three highly differentiated and divergent groups of Snowshoe Hares. These groups can correspond with evolutionarily significant units that might have evolved in separate refugia south and east of the Pleistocene ice sheets. Genetic diversity was highest at mid-latitudes of the species' range, and genetic uniqueness was greatest in southern populations, consistent with substructuring inferred from both mtDNA and microsatellite analyses at finer levels of analysis. Surprisingly, Snowshoe Hares in the Greater Pacific Northwest mtDNA lineage were more closely related to black-tailed jackrabbits (Lepus californicus) than to other Snowshoe Hares, which may result from secondary introgression or sHared ancestral polymorphism. Given the genetic distinctiveness of southern populations and minimal gene flow with their northern neighbours, fragmentation and loss of southern boreal habitats could mean loss of many unique alleles and reduced evolutionary potential.
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Influence of stand and landscape features on Snowshoe Hare abundance in fragmented forests
Journal of Mammalogy, 2011Co-Authors: C. W. Lewis, Karen E. Hodges, G. M. Koehler, L. S. MillsAbstract:Abstract Habitat fragmentation often separates and reduces populations of vertebrates, but the relative effects of habitat attributes within remnant patches versus the matrix surrounding the patches are less clear. For Snowshoe Hares (Lepus americanus) lower densities and disrupted cycles in their southern range have been ascribed to habitat fragmentation, although relevant scales of landscape influence remain unknown. In a fragmented forest in north-central Washington we counted fecal pellets of Snowshoe Hares to examine the extent to which relative Snowshoe Hare densities within stands of suitable habitat changed with the composition of surrounding habitats. Pellet densities were associated primarily with density of large shrubs and saplings and medium trees within a stand. Pellet densities also were correlated positively with the amount of moist forest (dominated by Engelmann spruce [Picea engelmannii] and subalpine fir [Abies lasiocarpa]) and correlated negatively with the amount of open-structured ha...
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Modelling the Canada lynx and Snowshoe Hare population cycle: the role of specialist predators
Theoretical Ecology, 2010Co-Authors: Rebecca Tyson, Sheena Haines, Karen E. HodgesAbstract:Mathematical models of the Snowshoe Hare ( Lepus americanus ) and Canada lynx ( Lynx canadensis ) population cycles in the boreal forest have largely focused on the interaction between a single specialist predator and its prey. Here, we consider the role that other Hare predators play in shaping the cycles, using a predator–prey model for up to three separate specialist predators. We consider the Canada lynx, coyote ( Canis latrans ) and great horned owl ( Bubo virginianus ). Our model improves on past modelling efforts in two ways: (1) our model solutions more closely represent the boreal Hare and predator cycles with respect to the cycle period, maximum and minimum Hare densities and maximum and minimum predator densities for each predator, and (2) our model sheds light on the role each specialist plays in regulation of the Hare cycle, in particular, the dynamics of the raptor appear to be crucial for characterising the low Hare densities correctly.
Charles J Krebs - One of the best experts on this subject based on the ideXlab platform.
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demography of Snowshoe Hare population cycles
Ecology, 2020Co-Authors: Madan K Oli, Charles J Krebs, Stan Boutin, Rudy Boonstra, Alice J Kenney, James E HinesAbstract:Cyclic fluctuations in abundance exhibited by some mammalian populations in northern habitats ("population cycles") are key processes in the functioning of many boreal and tundra ecosystems. Understanding population cycles, essentially demographic processes, necessitates discerning the demographic mechanisms that underlie numerical changes. Using mark-recapture data spanning five population cycles (1977-2017), we examined demographic mechanisms underlying the 9-10-yr cycles exhibited by Snowshoe Hares (Lepus americanus Erxleben) in southwestern Yukon, Canada. Snowshoe Hare populations always decreased during winter and increased during summer; the balance between winter declines and summer increases characterized the four, multiyear cyclic phases: increase, peak, decline, and low. Little or no recruitment occurred during winter, but summer recruitment varied markedly across the four phases with the highest and lowest recruitment observed during the increase and decline phase, respectively. Population crashes during the decline were triggered by a substantial decline in winter survival and by a lack of subsequent summer recruitment. In contrast, initiation of the increase phase was triggered by a twofold increase in summer recruitment abetted secondarily by improvements in subsequent winter survival. We show that differences in peak density across cycles are explained by differences in overall population growth rate, amount of time available for population growth to occur, and starting population density. Demographic mechanisms underlying Snowshoe Hare population cycles were consistent across cycles in our study site but we do not yet know if similar demographic processes underlie population cycles in other northern Snowshoe Hare populations.
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a plant toxin mediated mechanism for the lag in Snowshoe Hare population recovery following cyclic declines
Oikos, 2015Co-Authors: Donald L Deangelis, John P. Bryant, Charles J Krebs, Rongsong Liu, Stephen A Gourley, Paul B ReichardtAbstract:A necessary condition for a Snowshoe Hare population to cycle is reduced reproduction after the population declines. But the cause of a cyclic Snowshoe Hare population’s reduced reproduction during the low phase of the cycle, when predator density collapses, is not completely understood. We propose that moderate-severe browsing by Snowshoe Hares upon preferred winter-foods could increase the toxicity of some of the Hare’s best winter-foods during the following Hare low, with the result being a decline in Hare nutrition that could reduce Hare reproduction. We used a combination of modeling and experiments to explore this hypothesis. Using the shrub birch Betula glandulosa as the plant of interest, the model predicted that browsing by Hares during a Hare cycle peak, by increasing the toxicity B. glandulosa twigs during the following Hare low, could cause a Hare population to cycle. The model’s assumptions were verified with assays of dammarane triterpenes in segments of B. glandulosa twigs and captive Hare feeding experiments conducted in Alaska during February and March 1986. The model’s predictions were tested with estimates of Hare density and measurements of B. glandulosa twig growth made at Kluane, Yukon from 1988–2008. The empirical tests supported the model’s predictions. Thus, we have concluded that a browsing-caused increase in twig toxicity that occurs during the Hare cycle’s low phase could reduce Hare reproduction during the low phase of the Hare cycle.
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Snowshoe Hare pellet decay rates and aging in different habitats
Wildlife Society Bulletin, 2004Co-Authors: Laura R. Prugh, Charles J KrebsAbstract:Abstract Snowshoe Hare (Lepus americanus) pellet surveys are an efficient tool for monitoring population trends, but there is no standard methodology used to conduct surveys. To assist researchers in developing protocols, we evaluated pellet-decay rates and aging in 3 Snowshoe Hare habitat types in Alaska during the peak and decline of the Hare population from 1999–2002. We found significant differences in decay rates among habitat types and recommend measuring decay rates if pellet counts are to be compared among habitats or regions. Our experiments with known-age pellets indicated that pellets could not be aged reliably, but results from side-by-side comparisons of survey methods provided contrary evidence. Counts from uncleared plots, in which observers subjectively decided whether pellets were “new” (<1 year old), were not statistically different from counts on annually cleared plots. We evaluated 4 methods for conducting pellet surveys: 1) cleared plots with counts of “new” pellets; 2) cleared plots ...
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Snowshoe Hare pellet-decay rates and aging in different habitats
Wildlife Society Bulletin, 2004Co-Authors: Laura R. Prugh, Charles J KrebsAbstract:Abstract Snowshoe Hare (Lepus americanus) pellet surveys are an efficient tool for monitoring population trends, but there is no standard methodology used to conduct surveys. To assist researchers in developing protocols, we evaluated pellet-decay rates and aging in 3 Snowshoe Hare habitat types in Alaska during the peak and decline of the Hare population from 1999–2002. We found significant differences in decay rates among habitat types and recommend measuring decay rates if pellet counts are to be compared among habitats or regions. Our experiments with known-age pellets indicated that pellets could not be aged reliably, but results from side-by-side comparisons of survey methods provided contrary evidence. Counts from uncleared plots, in which observers subjectively decided whether pellets were “new” (
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INFLUENCE OF RELATEDNESS ON Snowshoe Hare SPACING BEHAVIOR
Journal of Mammalogy, 2003Co-Authors: Cole Burton, Charles J KrebsAbstract:Predation and food are dominant forces regulating Snowshoe Hare (Lepus americanus) population density, yet manipulations of these factors have not proven sufficient to explain all aspects of Hare population dynamics. Social interactions among Hares have often been dismissed as unimportant in population regulation, but the mechanisms and consequences of such interactions have not been well studied. In this study, we examined one aspect of social behavior in Snowshoe Hares that has been hypothesized to be important in the spacing behavior of other species of small mammals: interactions among related individuals. We sampled 68 Hares on two 7.3-ha grids in the southwest Yukon Territory during a cyclic peak phase of population density and used livetrapping and radiotelemetry to quantify spacing behavior. Hares were genotyped at 7 microsatellite DNA loci, and relatedness (r) among individuals was estimated and correlated with spacing. Average relatedness was low on both grids ( #0) because very few close kin were present. Hares were not more or less likely to associate with kin than they were with nonkin. The results were similar when males, females, adults, and juveniles were considered together or separately and are thus consistent with a lack of sex-biased dispersal in Snowshoe Hares. Kin are not clustered in Snowshoe Hare populations, thus interactions among kin do not likely have a strong influence on Hare spacing behavior. This study supports the idea that spacing behavior has little influence on Hare population dynamics, at least during the peak phase of the cycle.
Dennis L Murray - One of the best experts on this subject based on the ideXlab platform.
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Appendix D. Seasonal and annual variability in stable isotope ratios of Snowshoe Hare and red squirrel hair samples from Clearwater National Forest, Idaho, USA.
2016Co-Authors: James D. Roth, Dennis L Murray, John D. Marshall, David M. Nickerson, Todd D SteuryAbstract:Seasonal and annual variability in stable isotope ratios of Snowshoe Hare and red squirrel hair samples from Clearwater National Forest, Idaho, USA
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habitat quality and population density drive occupancy dynamics of Snowshoe Hare in variegated landscapes
Ecography, 2013Co-Authors: Daniel H Thornton, Aaron J Wirsing, James D. Roth, Dennis L MurrayAbstract:Th e infl uence of habitat quality and population density on occupancy dynamics may surpass that of traditional metrics of area and isolation, but often this is not considered explicitly in studies of spatially structured populations. In landscapes that are not easily characterized as binary habitat/non-habitat (e.g. variegated landscapes), this infl uence may be even more important and occur at both local and landscape levels. It follows that occupancy dynamics may be driven by disparate processes depending on how extinction or colonization relate to habitat quality and population density. We examined the relative infl uence of area, structural isolation, habitat quality, local population density, and neighborhood population density (i.e. population density in the landscape around a site) on the probability of extinction and colonization of Snowshoe Hare Lepus americanus across an expansive forest mosaic landscape (encompassing the northern third of Idaho). Habitat quality and population density were highly infl uential in determining extinction and colonization, whereas patch area and isolation were much less important. Sites with heavier vegetative cover at the site or landscape-level were more likely to be colonized and less likely to go extinct, and sites with greater local population density in the previous time step had lower probability of extinction. Sites embedded in high density neighborhoods also were less likely to go extinct, but not more likely to be colonized. We found a signifi cant interaction between local and neighborhood population density on extinction in 1 yr, suggesting that the strength of demographic rescue may vary dependent on local site densities. Our results add to a growing literature showing that factors outside of structural metrics of area and isolation are important drivers of occupancy dynamics. Given the multi-scaled infl uence of habitat quality and population density on occupancy dynamics, our work also indicates that research on Snowshoe Hare must extend beyond simply assessing local factors to understand the spatial dynamics of populations.
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assessment of potential bias with Snowshoe Hare fecal pellet plot counts
Journal of Wildlife Management, 2005Co-Authors: Dennis L Murray, Ethan Ellsworth, Arthur ZackAbstract:Abstract The fecal pellet-plot method has been used extensively for Snowshoe Hare (Lepus americanus) population studies across the species' range, but potential biases associated with the technique have not been addressed adequately. We studied Hare pellet-plots in northern Idaho to quantify pellet decomposition rates across environmental gradients, and conducted feeding trials on captive Hares to assess the role of diet on pellet production rates. We found that across our study area pellet numbers tended to be higher on plots with high vegetative cover, which likely was a reflection of Hare habitat choice rather than lesser pellet decomposition in such habitat. A pellet decomposition experiment indicated that pellet persistence was negatively related to moisture level, and that pellets produced by Hares during summer decomposed more quickly than those from winter. We found that only 19% of fecal pellets collected from plots located across northern Idaho were produced by Hares during winter. There was a c...
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estimating low density Snowshoe Hare populations using fecal pellet counts
Canadian Journal of Zoology, 2002Co-Authors: Dennis L Murray, Aaron J Wirsing, James D. Roth, Ethan Ellsworth, Todd D SteuryAbstract:Snowshoe Hare (Lepus americanus) populations found at high densities can be estimated using fecal pellet densities on rectangular plots, but this method has yet to be evaluated for low-density populations. We further tested the use of fecal pellet plots for estimating Hare populations by correlating pellet densities with estimated Hare numbers on 12 intensive study areas in Idaho; pellet counts from extensive transects (n = 615) across northern Idaho enabled rectangular plots (0.155 m2) to be compared with paired small (0.155 m2) and large (1 m2) circular plots (metre-circle plots). Metre-circle plots had higher pellet prevalence, lower sample variance, and lower estimates of pellet density than the other plot types. Transects comprising circular plots required less establishment time, and observer training reduced the pellet-count bias attributable to plot shape. The number of Hares occupying intensive study sites was correlated with pellet density on all plot types, but rectangular plots provided a slig...
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a demographic analysis of a southern Snowshoe Hare population in a fragmented habitat evaluating the refugium model
Canadian Journal of Zoology, 2002Co-Authors: Aaron J Wirsing, Todd D Steury, Dennis L MurrayAbstract:The allegedly noncyclic dynamics of southern Snowshoe Hare (Lepus americanus) populations may be ex- plained by a model invoking habitat fragmentation and facultative predation (the refugium model) under which animals dispersing from patches of preferred habitat fail to establish themselves because of predation by facultative carnivores. We compared the refugium model with a revised model invoking heavy on-site predation in preferred habitat as the proximal mechanism responsible for the stability of southern Snowshoe Hare populations. The survival and movements of Hares in a fragmented habitat in central Idaho were monitored via radiotelemetry on 6 sites differing in habitat quality (indexed by understory cover) from 1998 to 2000. In support of the revised model, predation rates were high irrespective of cover availability or Hare density, and predators did not kill dispersing animals disproportionately. Furthermore, predation was focused on small Hares, suggesting that poor recruitment of juveniles may be the mecha- nism ultimately responsible for the damped dynamics of southern Snowshoe Hare populations. The low survival rates we measured suggest that the population under study was undergoing a marked decline. However, the observed decline, determined by comparing study-site population estimates, was less severe, implying that the persistence of local snow - shoe Hare populations in some areas of the species' southern range may be influenced by metapopulation dynamics. Specifically, southern Snowshoe Hare populations in small patches of usable habitat may be prevented from going extinct by the arrival of immigrants from similar nearby patches.
Roger W Ruess - One of the best experts on this subject based on the ideXlab platform.
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functional responses of white spruce to Snowshoe Hare herbivory at the treeline
PLOS ONE, 2018Co-Authors: Justin Olnes, Knut Kielland, Helene Genet, Glenn P Juday, Roger W RuessAbstract:Herbivores can modify the rate of shrub and treeline advance. Both direct and indirect effects of herbivory may simultaneously interact to affect the growth rates of plants at this ecotone. We investigated the effect of Snowshoe Hare herbivory on the height of white spruce at two treeline locations in Alaska, USA. White spruce is expanding its distribution both upwards in elevation and northward in latitude because of climate warming, and Snowshoe Hares are already present in areas likely to be colonized by spruce. We hypothesized that herbivory would result in browsed individuals having reduced height, suggesting herbivory is a direct, negative effect on spruce treeline advance. We found an interactive effect between browsing history and spruce age. When young (under 30 years old), individuals that were browsed tended to be taller than unbrowsed individuals. However, older seedlings (over 30 years old) that had been browsed were shorter than unbrowsed individuals of the same age. Hares suppress faster growing individuals that are initially taller by preferentially browsing them as they emerge above the winter snowpack. This reduced height, in combination with increased mortality associated with browsing, is predicted to slow the advance of both latitudinal and altitudinal treeline expansions and alter the structure of treeline forests.
L. Scott Mills - One of the best experts on this subject based on the ideXlab platform.
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Conservation implications of the evolutionary history and genetic diversity hotspots of the Snowshoe Hare
Molecular ecology, 2014Co-Authors: Ellen Cheng, Karen E. Hodges, José Melo-ferreira, Paulo C. Alves, L. Scott MillsAbstract:With climate warming, the ranges of many boreal species are expected to shift northward and to fragment in southern peripheral ranges. To understand the conservation implications of losing southern populations, we examined range-wide genetic diversity of the Snowshoe Hare (Lepus americanus), an important prey species that drives boreal ecosystem dynamics. We analysed microsatellite (8 loci) and mitochondrial DNA sequence (cytochrome b and control region) variation in almost 1000 Snowshoe Hares. A hierarchical structure analysis of the microsatellite data suggests initial subdivision in two groups, Boreal and southwestern. The southwestern group further splits into Greater Pacific Northwest and U.S. Rockies. The genealogical information retrieved from mtDNA is congruent with the three highly differentiated and divergent groups of Snowshoe Hares. These groups can correspond with evolutionarily significant units that might have evolved in separate refugia south and east of the Pleistocene ice sheets. Genetic diversity was highest at mid-latitudes of the species' range, and genetic uniqueness was greatest in southern populations, consistent with substructuring inferred from both mtDNA and microsatellite analyses at finer levels of analysis. Surprisingly, Snowshoe Hares in the Greater Pacific Northwest mtDNA lineage were more closely related to black-tailed jackrabbits (Lepus californicus) than to other Snowshoe Hares, which may result from secondary introgression or sHared ancestral polymorphism. Given the genetic distinctiveness of southern populations and minimal gene flow with their northern neighbours, fragmentation and loss of southern boreal habitats could mean loss of many unique alleles and reduced evolutionary potential.
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Sinks without borders: Snowshoe Hare dynamics in a complex landscape
Oikos, 2009Co-Authors: Paul C. Griffin, L. Scott MillsAbstract:A full understanding of population dynamics of wide-ranging animals should account for the effects that movement and habitat use have on individual contributions to population growth or decline. Quantifying the per-capita, habitat-specific contribution to population growth can clarify the value of different patch types, and help to differentiate population sources from population sinks. Snowshoe Hares, Lepus americanus, routinely use various habitat types in the landscapes they inhabit in the contiguous US, where managing forests for high Snowshoe Hare density is a priority for conservation of Canada lynx, Lynx canadensis. We estimated density and demographic rates via mark-recapture live trapping and radio-telemetry within four forest stand structure (FSS) types at three study areas within heterogeneous managed forests in western Montana. We found support for known fate survival models with time-varying individual covariates representing the proportion of locations in each of the FSS types, with survival rates decreasing as use of open young and open mature FSS types increased. The per-capita contribution to overall population growth increased with use of the dense mature or dense young FSS types and decreased with use of the open young or open mature FSS types, and relatively high levels of immigration appear to be necessary to sustain Hares in the open FSS types. Our results support a conceptual model for Snowshoe Hares in the southern range in which sink habitats (open areas) prevent the buildup of high Hare densities. More broadly, we use this system to develop a novel approach to quantify demographic sources and sinks for animals making routine movements through complex fragmented landscapes.
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Precommercial Thinning Reduces Snowshoe Hare Abundance in the Short Term
Journal of Wildlife Management, 2007Co-Authors: Paul C. Griffin, L. Scott MillsAbstract:Abstract Management of young forests is not often considered in conservation plans, but young forests provide habitat for some species of conservation concern. Snowshoe Hares (Lepus americanus), critical prey of forest carnivores including the United States federally threatened Canada lynx (Lynx canadensis), can be abundant in young montane and subalpine forests with densely spaced saplings and shrub cover. Precommercial thinning (PCT) is a silvicultural technique that reduces sapling and shrub density on young forest stands. We tested for effects of PCT on Snowshoe Hare abundance for 2 years after experimental treatment at 3 replicate study areas. We also tested the effectiveness of a precommercial thinning with reserves (PCT-R) prescription, where 20% of the total stand was retained in uncut quarter-hectare patches. All stands were in montane–subalpine coniferous forests of western Montana, USA, where there is a persistent population of Canada lynx. Posttreatment changes in abundance were strongly negat...
