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Glucocorticoids and glucocorticoid metabolites are increasingly used to index physiological stress in wildlife. Although feces is often abundant and can be collected noninvasively, exposure to biotic and abiotic elements may influence fecal glucocorticoid metabolite (FGM) concentrations, leading to inaccurate conclusions regarding wildlife physiological stress. Using captive snowshoe hares (Lepus americanus) and simulated environmental conditions, we evaluated how different realistic field conditions and temporal sampling constraints might influence FGM concentrations using an 11-oxoetiocholanolone-enzyme immunoassay. We quantified how fecal pellet age (i.e., 0–6 days), variable summer temperatures, and precipitation affected FGM concentrations. Fecal pellet age had a strong effect on FGM concentrations (βAge = 0.395, s.d. = 0.085; β2Age = −0.061, s.d. = 0.012), which were lowest at the beginning and end of our exposure period (e.g., meanday6 = 37.7 ng/mg) and typically highest in the middle (meanday3 = 51.8 ng/mg). The effect of fecal pellet age on FGM concentrations varied across treatments with warm-dry and cool-wet conditions resulting in more variable FGM concentrations relative to control samples. Given the confounding effects of exposure and environmental conditions, if fresh fecal pellet collection is not an option, we encourage researchers to develop a temporally consistent sampling protocol to ensure all samples are exposed to similar environmental conditions. [ABSTRACT FROM AUTHOR]

Wildfires in conifer forests create patchy, heterogeneous landscapes. For many animal species, this post-fire variability means having to navigate quite different habitat patches to locate adequate cover and food. For snowshoe hares (Lepus americanus Erxleben, 1777), post-fire landscapes could include risky open patches, as well as dense regenerating stands rich in food and cover. We analyzed snowshoe hare tortuosity, speed of movement, and amount of browse along winter foraging pathways in unburned mature forest and in dense regenerating stands or open areas with sparse regeneration 12–13 years after the Okanagan Mountain Park fire (>25 000 ha near Kelowna, British Columbia, Canada) to determine whether hares change foraging behaviour in relation to cover type. Hares moved the fastest and browsed the least in open habitats. Hares browsed most often in areas where sapling regeneration was dense; their main forage was lodgepole pine (Pinus contorta Douglas ex Loudon). No differences were found in pathway tortuosity in relation to cover type (open, regenerating, or mature patches). When hares moved slower along foraging pathways, they also moved slightly more tortuously and ate more. These results suggest that hares prefer post-fire areas with dense tree regeneration. [ABSTRACT FROM AUTHOR]

Abstract Understanding basic energetic requirements of wildlife species is critical to evaluate how individuals persist in their current environments as well as to forecast responses to changed climates or habitats. Indeed, northern range limits are often thought to reflect harsh abiotic conditions that exceed the capacity of individuals to stay in energetic balance. Bobcats (Lynx rufus) occur across much of North America; at northern latitudes, they face winter challenges such as deep snows, cold temperatures, and possible food scarcity. We developed an energetics model from field data on movements, body mass, and observed diet of bobcats in mountains of northwest Montana, then evaluated overwinter prey requirements that would enable bobcats to stay in energy balance in this difficult environment. Our model indicated average daily energy expenditures were ~ 1.41× basal metabolic rate. For 90 days from December to February, a 10.5 kg bobcat consuming prey items in proportion with the observed diet for bobcats in this area would need about 2.1 kg of deer (Odocoileus spp.), 7 snowshoe hares (Lepus americanus), 155 red squirrels (Tamiasciurus hudsonicus), 9 woodrats (Neotoma cinerea), and 250 small rodents (Cricetidae). Bobcats have considerable flexibility in diet, movements, and both timing and duration of daily activity to adjust their energetic expenditures in winter. Highlights • Winter habitats with deep snow impose high travel and thermoregulatory costs on wildlife. • We modeled winter energetic costs for bobcats (Lynx rufus) in northwestern Montana. • Although energetic costs were high, bobcats were likely able to stay in energy balance. • Bobcats varied diets, movements, and habitat selection in winter. [ABSTRACT FROM AUTHOR]

Carrion consumption by herbivores is increasingly being observed in nature, however, we lack detailed analyses of its occurrence for numerous species. Here, we quantify incidences of scavenging by Snowshoe Hares (Lepus americanus) in Yukon, Canada between January 2015 and July 2017. Hares scavenged 12.4% of carcasses deployed and were more likely to scavenge during the winter. Hares consumed meat from a variety of different species, including Canada Lynx (Lynx canadensis), as well as the carcasses of hares. On one occasion, an individual repeatedly ingested feathers from a Spruce Grouse (Falcipennis canadensis) carcass. Scavenging by hares may result from food or nutrient limitations during winter months and appears relatively common when compared to other lagomorph species. [ABSTRACT FROM AUTHOR]

Abstract The San Juan Mountains of southern Colorado provide subalpine habitat for a suite of mammalian species including Canada lynx ( Lynx canadensis ), moose ( Alces alces ) and snowshoe hare ( Lepus americanus ). In the winter field season of 2016 five faecal samples from lynx, and one each from moose and snowshoe hare were collected to identify small single-stranded DNA viruses associated with these three prominent species. Thirty-two novel viruses were identified and classified as members of two well established ssDNA families Genomoviridae (n = 22) and Microviridae (n = 10) and one recently proposed new family, Smacoviridae (n = 1). In addition one highly novel circular ssDNA virus was identified which at present does not group with any known family. A high level of genomovirus diversity was identified from faeces collected between and across the three mammal species, with full genome-wide pairwise comparisons showing 57%–97% identity. Twenty genomoviruses can be assigned to the genus Gemycircularvirus and represent 11 species, and two into a distinct species in the genus Gemykolovirus. The single smacovirus identified from moose also represents a distinct smacovirus species. Ten microviruses, seven from moose, one from snowshoe hare and two from lynx, all are part of the Gokushovirinae subfamily. The two from lynx are highly similar to a microvirus previously detected in domestic cat (sharing 88%–90% genome-wide identity), indicating this may be a common felid gut microbiome associated virus. Our findings highlight the broad range of diverse ssDNA viruses present in three mammals inhabiting the San Juan Mountains. Highlights • Discovery of a diverse range of single-stranded DNA viruses in Canada lynx, moose, snowshoe hare • Characterization of twenty-two unique genomoviruses,one smacovirus and ten from the micorviruses • A novel divergent circular rep-encoding single-stranded DNA virus recovered from moose [ABSTRACT FROM AUTHOR]

Selection cutting is used in northern temperate forests where regeneration dynamics are driven by gap formation. By creating openings in the canopy, selection cutting modifies shrub cover, an important criterion in winter habitat selection by snowshoe hare (Lepus americanus Erxleben, 1777), a key species in North American forests. The objective of this study was to determine the effects of selection cuts on snowshoe hare habitat and to evaluate the restoration of habitat quality over time. Occurrence indices for snowshoe hare (fecal pellets and tracks) were modelled according to habitat quality parameters for 22 hardwood stands that were subjected to selection cutting between 1993 and 2007 and 30 untreated stands (15 hardwood and 15 mixedwood) in Abitibi-Témiscamingue, Quebec. Model selection based on the Akaike second-order information criterion (AICc) identified lateral cover as the only habitat structure parameter having a positive effect on snowshoe hare abundance in the study sites. Indicators of snowshoe hare presence were highest in untreated mixedwood stands but more abundant in selection cuts than in untreated hardwood stands. The use of selection cuts by snowshoe hare increased with time since logging was performed. We conclude that selection cutting exerted a positive effect on the use of hardwood stands by snowshoe hare. [ABSTRACT FROM AUTHOR]

Snowshoe hares (Lepus americanus) maintain seasonal camouflage by molting to a white winter coat, but some hares remain brown during the winter in regions with low snow cover. We show that cis-regulatory variation controlling seasonal expression of the Agouti gene underlies this adaptive winter camouflage polymorphism. Genetic variation at Agouti clustered by winter coat color across multiple hare and jackrabbit species, revealing a history of recurrent interspecific gene flow. Brown winter coats in snowshoe hares likely originated from an introgressed black-tailed jackrabbit allele that has swept to high frequency in mild winter environments. These discoveries show that introgression of genetic variants that underlie key ecological traits can seed past and ongoing adaptation to rapidly changing environments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Predation and predation risk can exert strong influences on the behavior of prey species. However, risk avoidance behaviors may vary among populations of the same species. We studied a population of snowshoe hares (Lepus americanus) near the southern edge of their range, in Pennsylvania. This population occupies different habitat types, experiences different environmental conditions, and are exposed to different predator species and densities than northern hare populations; therefore, they might exhibit differences in risk avoidance behaviors. We analyzed hare survival, movement rates, and habitat use under different levels of predation risk, as indexed by moonlight. Similar to previous work, we found snowshoe hare survival decreased with increased moon illumination during the winter, but we found differences in behavioral responses to increased predation risk. We found that snowshoe hares did not reduce movement rates during high‐risk nights, but instead found that hares selected areas with denser canopy cover, compared to low‐risk nights. We suggest that behavioral plasticity in response to predation risk allows populations of the same species to respond to localized conditions. [ABSTRACT FROM AUTHOR]

Though fishers Pekania pennanti were extirpated from most of their historical range in the United States, they have successfully repatriated many areas, and are now legally harvested in the Great Lakes region. Recent harvests and winter track surveys, however, suggest fisher populations may again be decreasing in northern Wisconsin. We investigated potential factors contributing to this purported decrease by quantifying fisher diet in northern Wisconsin via stable isotope analysis (δ13C and δ15N) and examining body condition of individual fishers using measurements of fat depots. Diet reconstruction revealed small mammals and porcupines constitute the largest portions of fishers' diets in Wisconsin. Body condition analyses showed that contemporary fishers carry significantly less body fat compared to Wisconsin fishers two decades ago and to two other regional populations. Our findings contrast with past regional studies that report snowshoe hares and white-tailed deer carrion as the largest components of fisher diet. We suggest the diet and body condition of fishers in Wisconsin could be due to low availability of preferred prey other than porcupines on the landscape, which may be contributing to the recent putative population decrease. [ABSTRACT FROM AUTHOR]

Population cycles are one of nature's great mysteries. For almost a hundred years, innumerable studies have probed the causes of cyclic dynamics in snowshoe hares, voles and lemmings, forest Lepidoptera and grouse. Even though cyclic species have very different life histories, similarities in mechanisms related to their dynamics are apparent. In addition to high reproductive rates and density-related mortality from predators, pathogens or parasitoids, other characteristics include transgenerational reduced reproduction and dispersal with increasing-peak densities, and genetic similarity among populations. Experiments to stop cyclic dynamics and comparisons of cyclic and noncyclic populations provide some understanding but both reproduction and mortality must be considered. What determines variation in amplitude and periodicity of population outbreaks remains a mystery. [ABSTRACT FROM AUTHOR]

Previous gold mining activities and arsenopyrite ore roasting activities at the Giant mine site (1948 to 2004) resulted in the release of high amounts of arsenic and trace metals into the terrestrial and aquatic ecosystems of Yellowknife, Northwest Territories, Canada. While elevated levels of arsenic has been consistently reported in surface soils and vegetation near the vicinity of the Giant mine area and in surrounding locations, systematic studies evaluating the overall health status of terrestrial small mammals endemic to the area are lacking. The purpose of this present study was to evaluate and comparatively assess the biochemical responses and histopathological effects induced by chronic arsenic and cadmium exposure in wild snowshoe hares breeding near the city of Yellowknife, specifically around the vicinity of the abandoned Giant mine site and in reference locations. Analysis included measurement of total arsenic and cadmium concentration in nails, livers, kidneys, bones, stomach content of hares, in addition to histopathological evaluation of hepatic and ocular lesions. Biochemical responses were determined through measurement of lipid peroxidation levels and antioxidant enzymes activities (catalase, superoxide dismutase, glutathione peroxidase, and glutathione disulfide). The results revealed that arsenic concentration was 17.8 to 48.9 times higher in the stomach content, and in the range of 4 to 23 times elevated in the nails of hares from the mine area compared to the reference location. Arsenic and cadmium levels were also noted to be increased in the bones, renal and hepatic tissues of hares captured near the mine area compared to the reference site. Specifically, hares from the mine area showed nail cadmium levels that was 2.3 to 17.6 times higher than those from the reference site. Histopathological examination of the eyes revealed no specific ocular lesions, such as lens opacity (cataracts) or conjunctivitis; however, hares from both locations exhibited hepatic steatosis (fatty liver change). Lipid peroxidation levels were relatively increased and accompanied with reduced antioxidant enzyme activities in hares from the mine area compared to the hares from the reference site. The results of this preliminary study suggest that the snowshoe hares breeding near the vicinity of Yellowknife, including near the Giant mine area have been chronically exposed to elevated levels of arsenic and cadmium, which consequently led to the increased levels of oxidative stress and perturbation of antioxidant defense system in exposed animals. The results of this present study constitute the first observation of chronic arsenicosis in wild small mammal species in Canada. [ABSTRACT FROM AUTHOR]

Predators play a critical, top–down role in shaping ecosystems, driving prey population and community dynamics. Traditionally, studies of predator‐prey interactions have focused on direct effects of predators, namely the killing of prey. More recently, the non‐consumptive effects of predation risk are being appreciated; e.g. the ‘ecology of fear’. Prey responses to predation risk can be morphological, behavioural, and physiological, and are assumed to come at a cost to prey fitness. However, few studies have examined the relationship between predation risk and survival in wild animals. We tested the hypothesis that predation risk itself could reduce survival in wild‐caught snowshoe hares. We exposed female snowshoe hares to a simulated predator (a trained dog) during gestation only, and measured adult survival and, in surviving females, their ability to successfully wean offspring. We show for the first time in a wild mammal that the risk of predation can itself be lethal. Predation risk reduced adult female survival by 30%, and had trans‐generational effects, reducing offspring survival to weaning by over 85% – even though the period of risk ended at birth. As a consequence of these effects the predator‐exposed group experienced a decrease in number, while the control group substantially increased. Challenges remain in determining the importance of risk‐induced mortality in natural field settings; however, our findings show that non‐lethal predator encounters can influence survival of both adults and offspring. Future work is needed to test these effects in free‐living animals. [ABSTRACT FROM AUTHOR]

ABSTRACT: Prescribed burning has the potential to improve habitat for species that depend on pyric ecosystems or other early successional vegetation types. For species that occupy diverse plant communities over the extent of their range, response to disturbances such as fire might vary based on post‐disturbance vegetation dynamics among plant communities. Although responses of snowshoe hares (Lepus americanus) to fire have been studied in conifer‐dominated forests in northern parts of the species’ range, there is a lack of information on snowshoe hare habitat use in fire‐dependent communities in southern parts of their range. We used global positioning system (GPS) and very high frequency (VHF) radio‐collars to monitor the habitat use of 32 snowshoe hares in a scrub‐oak (Quercus ilicifolia)‐pitch pine (Pinus rigida) barrens complex in northeastern Pennsylvania where prescribed fire has been used for habitat restoration. The area contained stands that underwent prescribed burning 1–6 years prior to our study. Also, we investigated fine‐scale determinants of habitat use within stands. We found that regardless of season, hares did not select for areas that had been burned within 6 years prior. Hares primarily used stands of older scrub oak, conifer, or hardwoods, which contained dense understory vegetation and canopy cover. Hare habitat use also was positively associated with stand edges. Our results suggest that hares do not respond to prescribed burning of scrub oak in the short‐term. In addition, by focusing on structural determinants of habitat use, rather than broad‐scale characteristics such as stand type, management strategies for snowshoe hares can be adapted over the extent of their range despite the multitude of different land cover types across which the species occurs. © 2017 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Vertebrate populations throughout the circumpolar north often exhibit cyclic dynamics, and predation is generally considered to be a primary driver of these cycles in a variety of herbivore species. However, weather and climate play a role in entraining cycles over broad landscapes and may alter cyclic dynamics, although the mechanism by which these processes operate is uncertain. Experimental and observational work has suggested that weather influences primary productivity over multi-year time periods, suggesting a pathway through which weather and climate may influence cyclic herbivore dynamics. Using long-term monitoring data, we investigated the relationships among multi-year weather conditions, measures of primary productivity, and the abundance of two cyclic herbivore species: snowshoe hare and northern red-backed vole. We found that precipitation (rain and snow) and growing season temperatures were strongly associated with variation in primary productivity over multi-year time horizons. In turn, fourfold variation in the amplitude of both the hare and vole cycles observed in our study area corresponded to long-term changes in primary productivity. The congruence of our results for these two species suggests a general mechanism by which weather and climate might influence cyclic herbivore population dynamics. Our findings also suggested that the association between climate warming and the disappearance of cycles might be initiated by changes in primary productivity. This work provides an explanation for observed influences of weather and climate on primary productivity and population cycles and will help our collective understanding of how future climate warming may influence these ecological phenomena in the future. [ABSTRACT FROM AUTHOR]

Though fishers Pekania pennanti were extirpated from most of their historical range in the United States, they have successfully repatriated many areas, and are now legally harvested in the Great Lakes region. Recent harvests and winter track surveys, however, suggest fisher populations may again be decreasing in northern Wisconsin. We investigated potential factors contributing to this purported decrease by quantifying fisher diet in northern Wisconsin via stable isotope analysis (δ13C and 615N) and examining body condition of individual fishers using measurements of fat depots. Diet reconstruction revealed small mammals and porcupines constitute the largest portions of fishers' diets in Wisconsin. Body condition analyses showed that contemporary fishers carry significantly less body fat compared to Wisconsin fishers two decades ago and to two other regional populations. Our findings contrast with past regional studies that report snowshoe hares and white-tailed deer carrion as the largest components of fisher diet. We suggest the diet and body condition of fishers in Wisconsin could be due to low availability of preferred prey other than porcupines on the landscape, which may be contributing to the recent putative population decrease. [ABSTRACT FROM AUTHOR]

Various bone abnormalities, including osteoporosis, have been associated with chronic arsenic and cadmium exposure in experimental animal models, but information regarding the bone pathology of wild population of small mammals breeding in contaminated environment is limited. This present study was conducted to comparatively assess the prevalence and pattern of skeletal abnormalities in free ranging snowshoe hares inhabiting an area heavily contaminated by arsenic and other trace metals, near the vicinity of the abandoned Giant mine, and in a reference location approximately 20 km from the city of Yellowknife, Northwest Territories, Canada. The femur and vertebrae of snowshoe hares from the mine area and reference location were subjected to bone densitometry examination and biomechanical testing using dual energy X-ray absorptiometry (DXA) and 3-point bending test. t -test results indicated that femoral densitometry parameters such as bone mineral density (BMD) ( p = 0.5), bone mineral content (BMC) ( p = 0.675), bone area (BA) ( p = 0.978) and tissue area (TA) ( p = 0.549) were not significantly different between locations. All densitometry parameters of the vertebrae (BMD, BA and TA) differed between locations ( p < 0.05), except for BMC ( p = 0.951) which showed no significant difference between the two locations. Vertebrae from the mine area also showed relatively lower BA and TA compared to the reference location. A constellation of skeletal abnormalities were also observed along the axial and appendicular bones respectively. Specifically, growth defects, osteoporosis, cortical fractures, sclerosis, and cyst like changes were commonly observed in the femurs and vertebrae of hares from both locations. With respect to biomechanical properties, only bone stiffness and peak load tended to be relatively reduced in specimens from the mine area, whereas work to failure was notably increased in specimens from the reference site compared to those from the mine area. Taken together, the results of this preliminary study suggest that chronic concomitant exposure to arsenic and cadmium may be involved in the etiology of various bone abnormalities, including osteoporosis in wild population of snowshoe hares from the Yellowknife area. The result presented in this study represent the first evaluation of osteological effects in free-ranging furbearers (snowshoe hares) diagnosed with arsenicosis, and concomitantly exposed to environmental levels of cadmium. [ABSTRACT FROM AUTHOR]

Ideal free distribution theory predicts that increased conspecific density redistributes individuals to low-density, suboptimal habitat. However, possible lags in response to population density remain poorly documented. Snowshoe hares (Lepus americanus) may exhibit density-dependent habitat selection due to its marked variation in population density. Based on 11 years (2004–2014) of snow tracking in Quebec (Canada), we investigated snowshoe hares’ short-term and delayed habitat selection responses to population density. We predicted that at high densities, hare distribution expands into low-density habitat, thus weakening the association between hares and high-density habitat. We surveyed hare tracks along 95 km of transects on average each year and georeferenced 14,240 tracks. We used Generalized Estimating Equations for track count per 100 m transect segment as a function of the proportion of different forest age classes (0–20 y, 20–40 y and 40–80 y) within 50 m of the segments. We used model coefficients for each age class as a measure of habitat preference, and modeled those coefficients as a function of a population density index in current and previous winters. Coefficients for 20- to 40-y-old forests were positive each year, indicating that this habitat was preferred. The association between track counts and 20- to 40-y-old forest significantly declined with density during the previous winter, suggesting that hare spread from preferred forest with a lagged response to density. To our knowledge, no previous empirical studies have documented a lagged habitat selection response to population density. Time lags offer possible explanation for documented deviations from ideal free distribution models. [ABSTRACT FROM AUTHOR]

Population cycles have long fascinated ecologists from the time of Charles Elton in the 1920s. The discovery of large population fluctuations in undisturbed ecosystems challenged the idea that pristine nature was in a state of balance. The 10-year cycle of snowshoe hares ( Lepus americanus Erxleben) across the boreal forests of Canada and Alaska is a classic cycle, recognized by fur traders for more than 300 years., Since the 1930s, ecologists have investigated the mechanisms that might cause these cycles. Proposed causal mechanisms have varied from sunspots to food supplies, parasites, diseases, predation and social behaviour. Both the birth rate and the death rate change dramatically over the cycle. Social behaviour was eliminated as a possible cause because snowshoe hares are not territorial and do not commit infanticide., Since the 1960s, large-scale manipulative experiments have been used to discover the major limiting factors. Food supply and predation quickly became recognized as potential key factors causing the cycle. Experiments adding food and restricting predator access to field populations have been decisive in pinpointing predation as the key mechanism causing these fluctuations., The immediate cause of death of most snowshoe hares is predation by a variety of predators, including the Canada lynx ( Lynx canadensis Kerr). The collapse in the reproductive rate is not due to food shortage as was originally thought, but is a result of chronic stress from predator chases., Five major issues remain unresolved. First, what is the nature of the predator-induced memory that results in the prolonged low phase of the cycle? Second, why do hare cycles form a travelling wave, starting in the centre of the boreal forest in Saskatchewan and travelling across western Canada and Alaska? Third, why does the amplitude of the cycle vary greatly from one cycle to the next in the same area? Fourth, do the same mechanisms of population limitation apply to snowshoe hares in eastern North American or in similar ecosystems across Siberia? Finally, what effect will climatic warming have on all the above issues? The answers to these questions remain for future generations of biologists to determine. [ABSTRACT FROM AUTHOR]

Wolves ( Canis lupus) are opportunistic predators and will capitalize on available abundant food sources. However, wolf diet has primarily been examined at monthly, seasonal, or annual scales, which can obscure short-term responses to available food. We examined weekly wolf diet from late June to early October by collecting scats from a single wolf pack in northeastern Minnesota. During our 15 wk study, nonungulate food types constituted 58% of diet biomass. Deer ( Odocoileus virginianus) fawns were a major food item until mid-July after which berries (primarily Vaccinium and Rubus spp.) composed 56-83% of weekly diet biomass until mid-August. After mid-August, snowshoe hares ( Lepus americanus) and adult deer were the primary prey. Weekly diet diversity approximately doubled from June to October as wolves began using several food types in similar proportions as the summer transitioned into fall. Recreational hunting of black bears ( Ursus americanus) contributed to weekly wolf diet in the fall as wolves consumed foods from bear bait piles and from gut piles/carcasses of successfully harvested or fatally wounded bears. To our knowledge, we are the first to examine wolf diet via scat analysis at weekly intervals, which enabled us to provide a detailed description of diet plasticity of this wolf pack, as well as the rapidity with which wolves can respond to new available food sources. [ABSTRACT FROM AUTHOR]

Abstract: Old‐growth western larch has been degraded throughout much of its historic range due to extensive timber harvest and fire suppression. We examined the effects of a restoration treatment of western larch on snowshoe hares, a denizen of the boreal forest serving as a focal animal species to indicate the health of the restored ecosystem. We implemented a restoration treatment using “doughnut thinning” to accelerate development of old‐growth attributes in larch stands and simultaneously examined the short‐term effects on snowshoe hare density, survival, and movement. Although typical forest management activities tend to have adverse effects on hares especially in the short term, we found that the restoration treatment did not affect hare density or survival in the short term. In addition, despite significant decreases in cover coinciding with the larch needle drop, we found evidence of year‐round immigration into larch stands by hares suggesting larch stands are suitable year‐round hare habitat. Taken together, our findings suggest that a larch restoration treatment designed to accelerate the development of old‐growth attributes can be implemented so as to have no measurable short‐term detrimental effects on hares. [ABSTRACT FROM AUTHOR]

The Snowy Owl ( Bubo scandiacus) is a circumpolar raptor that nests in Arctic tundra. Satellite tracking of nesting Snowy Owls in Alaska and eastern Canada has allowed researchers to document the widely nomadic movements of these owls between summer and winter ranges. This study expands that knowledge for Snowy Owls in the western Canadian Arctic. Based on previous studies, we predicted that owls: (1) would not have strong fidelity to specific winter or summer ranges; (2) would travel widely in search of breeding and nonbreeding areas at which they would settle for considerable time (months); (3) would choose areas to settle based on prey concentration; and (4) would use a mix of overwintering strategies, with some staying in Arctic and boreal regions, and some migrating south. Movement patterns of four female owls captured at nesting sites on Herschel Island, Yukon Territory, Canada, supported the first two predictions. The third prediction was partly supported: some sites of summer settlement were located where prey was relatively abundant, whereas other selected sites did not appear to have enough prey for successful nesting. The latter sites may have been the best available in those areas, however. Sites of winter settlement generally overlapped regions with high abundance of snowshoe hares ( Lepus americanus) or ptarmigan ( Lagopus spp.), and were located in relatively open alpine, subalpine, or wetland environments, where prey were likely most accessible. Contrary to our last prediction, all four study owls settled in boreal Alaska and the northern Yukon Territory. This pattern contrasts with observations that eastern North American Snowy Owls rarely wintered in the boreal biome. This study highlights the need to better understand the habitat choices and food habits of wintering Snowy Owls in the northern boreal mountains. [ABSTRACT FROM AUTHOR]

Deep snow can reduce accessibility to vegetation and cover by herbivores by blanketing understory cover, yet simultaneously increase access to foliage at higher levels. Thus, snow depth fluctuation should lead to spatiotemporal variation in herbivore habitat use. We measured shifts in habitat use by snowshoe hare ( Lepus americanus Erxleben, 1777) as a function of snow depth in an eastern Canadian boreal forest where snow depth often exceeds 1 m. We hypothesized that as snow accumulates, snowshoe hares shift from locations with dense vegetation just above ground to locations with dense vegetation higher above ground. We surveyed 58 km of transects over three winters and found 1954 hare tracks. We analyzed track counts as a response to a density index of low vegetation (0-1.5 m above ground), high vegetation (2-4 m above ground), predator tracks, and snow depth. We found more hare tracks in sites with dense high vegetation when snow was deeper, and more hare tracks in sites with dense low vegetation when snow was shallower. Predator track presence did not influence responses to snow depth. Snow depth dynamics can drive hare distribution, and in turn, introduce uncertainty in spatial distribution models for the species and possibly its interactions with predators. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the impact of climate change on winter survival of prey species, snowshoe hare in Yukon's Kluane Lake region in Canada. It mentions that very high frequency (VHF) telemetry was used to monitor survival of hares. It notes that prediction of climate-driven impacts on the survival of snowshoe hare is important given the significance of prey species as food source in boreal forest.

Age at primiparity is a flexible life-history trait that purportedly responds to changing population dynamics and variable resource abundance. We examined placental scars in yearling Canada lynx ( Lynx canadensis (Kerr, 1792)) from the island of Newfoundland and used pregnancy rates and litter sizes to indicate primiparity. We modelled these lynx productivity data with snowshoe hare ( Lepus americanus Erxleben, 1777) population attributes using seven multiple a priori competing hypotheses. Hare abundance showed peak, decline, and increase phases, and densities based on capture-mark-recapture estimates ranged from 0.11 to 1.19 hares·ha−1. Overall, yearling pregnancy rate was 23.5% and the model with hare abundance fitted alone had the most support. However, surprisingly hare abundance explained little (6%) variation in yearling pregnancy rate. Mean (±SE) litter size was 3.51 ± 0.27. None of our covariate models provided unequivocal support for predicting yearling litter size. We speculate that individuals may exhibit behavioural plasticity such that they can dampen the impact of primary prey abundance on yearling pregnancy rate by exploiting alternate prey. Furthermore, intraspecific social interactions may provide additional insight into the determinants of pregnancy rate in yearling lynx. [ABSTRACT FROM AUTHOR]

Treelines in Alaska are advancing in elevation and latitude because of climate warming, which is expanding the habitat available for boreal wildlife species, including snowshoe hares ( Lepus americanus). Snowshoe hares are already present in tall shrub communities beyond treeline and are the main browser of white spruce ( Picea glauca), the dominant tree species at treeline in Alaska. We investigated the processes involved in a 'snowshoe hare filter' to white spruce establishment near treeline in Denali National Park, Alaska, USA. We modeled the pattern of spruce establishment from 1970 to 2009 and found that fewer spruce established during periods of high hare abundance. Multiple factors interact to influence browsing of spruce, including the hare cycle, snow depth and the characteristics of surrounding vegetation. Hares are abundant at treeline and may exclude spruce from otherwise optimal establishment sites, particularly floodplain locations with closed shrub canopies. The expansion of white spruce treeline in response to warming climate will be strongly modified by the spatial and temporal dynamics of the snowshoe hare filter. [ABSTRACT FROM AUTHOR]

Seasonal coat colour change is an important adaptation to seasonally changing environments but the evolution of this and other circannual traits remains poorly understood. In this study, we use gene expression to understand seasonal coat colour moulting in wild snowshoe hares ( Lepus americanus). We used hair colour to follow the progression of the moult, simultaneously sampling skin from three moulting stages in hares collected during the peak of the spring moult from white winter to brown summer pelage. Using RNA sequencing, we tested whether patterns of expression were consistent with predictions based on the established phases of the hair growth cycle. We found functionally consistent clustering across skin types, with 766 genes differentially expressed between moult stages. 'White' pelage showed more differentially expressed genes that were upregulated relative to other skin types, involved in the transition between late telogen (quiescent stage) and the onset of anagen (proliferative stage). Skin samples from transitional 'intermediate' and 'brown' pelage were transcriptionally similar and resembled the regressive transition to catagen (regressive stage). We also detected differential expression of several key circadian clock and pigmentation genes, providing important means to dissect the bases of alternate seasonal colour morphs. Our results reveal that pelage colour is a useful biomarker for seasonal change but that there is a consistent lag between the main gene expression waves and change in visible coat colour. These experiments establish that developmental sampling from natural populations of nonmodel organisms can provide a crucial resource to dissect the genetic basis and evolution of complex seasonally changing traits. [ABSTRACT FROM AUTHOR]

Understanding adaptations of nonhibernating northern endotherms to cope with extreme cold is important because climate-induced changes in winter temperatures and snow cover are predicted to impact these species the most. We compared winter pelage characteristics and heat production of snowshoe hares ( Lepus americanus Erxleben, 1777) on the southern edge of their range, in Pennsylvania (USA), to a northern population, in the Yukon (Canada), to investigate how hares might respond to changing environmental conditions. We also investigated how hares in Pennsylvania altered movement rates and resting spot selection to cope with variable winter temperatures. Hares from Pennsylvania had shorter, less dense, and less white winter coats than their northern counterparts, suggesting lower coat insulation. Hares in the southern population had lower pelage temperatures, indicating that they produced less heat than those in the northern population. In addition, hares in Pennsylvania did not select for resting spots that offered thermal advantages, but selected locations offering visual obstruction from predators. Movement rates were associated with ambient temperature, with the smallest movements occurring at the lower and upper range of observed ambient temperatures. Our results indicate that snowshoe hares may be able to adapt to future climate conditions via changes in pelage characteristics, metabolism, and behavior. [ABSTRACT FROM AUTHOR]

Snowshoe hares ( Lepus americanus) are an ecologically important herbivore because they modify vegetation through browsing and serve as a prey resource for multiple predators. We implemented a multiscale approach to characterize habitat relationships for snowshoe hares across the mixed conifer landscape of the northern Rocky Mountains, USA. Our objectives were to (1) assess the relationship between horizontal cover and snowshoe hares, (2) estimate how forest metrics vary across the gradient of snowshoe hare use and horizontal cover, and (3) model and map snowshoe hare occupancy and intensity of use. Results indicated that both occupancy and intensity of use by snowshoe hares increased with horizontal cover and that the effect became stronger as intensity of use increased. This underscores the importance of dense horizontal cover to achieve high use, and likely density, of snowshoe hares. Forest structure in areas with high snowshoe hare use and horizontal cover was characterized as multistoried with dense canopy cover and medium-sized trees (e.g., 12.7-24.4 cm). The abundance of lodgepole pine ( Pinus contorta) was associated with snowshoe hare use within a mixed conifer context, and the only species to increase in abundance with horizontal cover was Engelmann spruce ( Picea engelmannii) and subalpine fir ( Abies lasiocarpa). Our landscape-level modeling produced similar patterns in that we observed a positive effect of lodgepole pine and horizontal cover on both occupancy and use by snowshoe hares, but we also observed a positive yet parabolic effect of snow depth on snowshoe hare occupancy. This work is among the first to characterize the multiscale habitat relationships of snowshoe hares across a mixed conifer landscape as well as to map their occupancy and intensity of use. Moreover, our results provide stand- and landscape-level insights that directly relate to management agencies, which aids in conservation efforts of snowshoe hares and their associated predators. [ABSTRACT FROM AUTHOR]

Information on climate that influences snowshoe hares ( Lepus americanus Erxleben, 1777) can inform adaptation strategies. We identified climate factors correlated with localized changes in occupancy of snowshoe hares in Michigan, USA. A change in occupancy occurred if a site (∼7.5 ha) knowingly occupied by hares sometime in the past became unoccupied. We used local ecological knowledge to map sites where hares historically occurred and to assign a year of last-known occupancy. At 134 historically occupied sites, we conducted snow track surveys in 2013 to determine current occupancy status. We identified climate variables having relevance to hare population demographics and modeled the likelihood that those variables influenced current occupancy status. The top-ranking model included maximum temperature from 15 May to 19 January; as maximum temperature increased, the likelihood of a site becoming unoccupied increased. The second-ranked model included total number of days with measurable snow on the ground; as days with snow on the ground decreased, the likelihood of a site becoming unoccupied increased. Our data indicated that site occupancy status of hares can be described by climate variables and that the southern edge of snowshoe hare distribution in Michigan shifted northward by ∼45 km over the last 20 years. [ABSTRACT FROM AUTHOR]

The Canada Lynx ( Lynx canadensis) is poorly documented in southwest Alaska, where dominant habitats are generally not conducive to supporting persistent Snowshoe Hare ( Lepus americanus) or Lynx populations. We compiled recent and historic records from southwest Alaska that collectively suggest that persistent Lynx populations occur at the base of the Alaska Peninsula where boreal forest transitions to open tundra habitats. Records show that Lynx, at least periodically, also occur throughout the entirety of the Alaska Peninsula and that a self-sustaining and relatively isolated population occurs in an isolated stand of Poplar forest near Mother Goose Lake, which probably represents one of the westernmost Lynx populations in North America. These records extend the known distribution of the species by approximately 380 km southwest along the Alaska Peninsula. These records also suggest that Lynx occur in areas where Snowshoe Hare are rare or absent, and that other prey species may facilitate the persistence of distinct population segments at the extent of their range in Alaska. [ABSTRACT FROM AUTHOR]

ABSTRACT Information regarding the diet of Canada lynx ( Lynx canadensis) at the southernmost extent of its range is critical for managing the species under current and predicted climate conditions. Therefore, from 1999-2009, we investigated winter diet and hunting strategies of Canada lynx in Colorado, USA by tracking individuals in the snow to identify sites where lynx encountered and killed prey. Similar to other parts of lynx range, snowshoe hares ( Lepus americanus) were the primary winter food in Colorado, especially when considering total biomass consumed. Red squirrels ( Tamiasciurus hudsonicus) comprised the bulk of the remaining food items and were a substantial occurrence during several years, which is consistent with previous hypotheses regarding the diet of lynx in southerly populations. Lynx successfully captured snowshoe hares on 31% of attempts and red squirrels on 47% of attempts, similar to lynx in other regions. In contrast to other populations, the majority of chases of both prey species were initiated while actively hunting rather than by ambush and this behavior did not change through time. We found evidence for snowshoe hare refugia during winter; hunting success for hares peaked at sites with approximately 3,000 stems/ha, but was lower in more dense vegetation where hare densities were greater. Given this finding and the apparent importance of red squirrels as alternate prey, we suggest that management for lynx in the southern Rocky Mountains, USA, focus on maintenance of mature, uneven-aged Engelmann spruce ( Picea engelmannii)-subalpine fir ( Abies lasiocarpa) stands. Such stands naturally provide patches of dense and open habitats juxtaposed closely together that should simultaneously facilitate high hare densities (and refuge from predation) and accessibility to hares by lynx. Mature trees in such stands also provide abundant cone crops to sustain populations of red squirrels for use as alternate prey. © 2016 The Authors. Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society. [ABSTRACT FROM AUTHOR]

ABSTRACT Range boundaries are a manifestation of species' tolerances to environmental factors, including climate and human disturbance. As such, studying populations persisting along range boundaries can provide important insights into species' sensitivity to environmental change. Because multiple environmental influences may contribute to a range limit, studies focusing on range boundaries can guide management and conservation of these critical populations. To this end, we quantified the environmental factors associated with snowshoe hare ( Lepus americanus) occurrence at their southern range limit in Wisconsin. We surveyed 199 locations across a regional southern range boundary of snowshoe hares and analyzed the data within an occupancy modeling framework to test the hypothesis that this range boundary results from an interaction between winter climate and land cover. We found that dense vegetation structure and increasing forest and snow cover duration had positive effects on snowshoe hare occupancy along their southern range boundary, supporting our prediction that a suite of abiotic factors is associated with the southerly distribution of this winter-adapted mammal. These effects were additive and we found limited support for climate-land cover interactions, forest composition, winter snow depth, or predator occurrence. Spatial predictions of occupancy using only forest and snow cover variables denote a sharp range boundary, further illustrating the importance of these variables in shaping this species distribution. Our results highlight an important vulnerability of snowshoe hares to future climate change, and options for mediating this vulnerability through the maintenance of early successional habitat and forested landscapes along their southern range boundary. © 2016 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Certain herbivores and their predators undergo high amplitude periodic fluctuations in abundance in northern latitudes but exhibit damped cyclic dynamics in their respective southern ranges. Generalist predators and habitat disturbance have been identified as two features of southern habitats that may contribute to the attenuation of cycles in southern latitudes. Using the snowshoe hare and Canada lynx as model species, we employed a reaction–diffusion–advection framework with reaction terms taken from the May and Rosenzweig–MacArthur models to study the relative and joint damping impacts of generalist predation and habitat loss on predator–prey cycles. We found that generalist predation has consistently strong stabilizing effects and may represent a threat to the persistence of specialized predators. Habitat loss also ultimately results in the loss of cycles, but cycle amplitude and animal densities may not always decrease monotonically with habitat loss. The joint damping impacts of generalists and habitat loss can be severe, consistent with observations of low cycle amplitude, high predation rates, and significant habitat loss in the southern ranges of cyclic species. Elevated generalist predation rates at patch edges and in the surrounding matrix hasten cycle attenuation in situations that lead to increased prey exposure to generalists, including small patch sizes, higher movement rates into the matrix, and increased prey density at patch edges. The dominant driver of cycle attenuation, as well as cycle response to habitat disturbance, may vary between regions and systems. Field data that help clarify the relationships between habitat loss and fragmentation, generalist density and behavior, and cyclic activity would be invaluable in informing future modeling and conservation efforts. [ABSTRACT FROM AUTHOR]

In Pennsylvania, Lepus americanus (Snowshoe Hare) is near the southern limits of its range and at risk of range contraction because of loss of early-successional forest and impacts of climate change. We used hunter-harvest data to investigate changes in the distribution of Snowshoe Hare in Pennsylvania (1983-2011), forest inventory and land-use data to assess changes in amount and distribution of early-successional forest (1988-2011), and occupancy modeling (2004) to identify habitat and climate variables that explain the current distribution of Snowshoe Hare. We determined presence of Snowshoe Hare based on visual sightings, observations of tracks, and DNA analysis of fecal pellets, and used repeated visits to sampling sites and occupancy models to estimate occupancy rates (Ψ). Hunter-harvest data indicated the range of Snowshoe Hare in Pennsylvania contracted towards northwestern and northeastern portions of the state. Based on occupancy modeling, Snowshoe Hare were most likely to occupy early-successional and mixed deciduous-coniferous forest types and areas with colder winter temperatures, which coincided with the distribution of hunter harvests. Among the 4 forest types, we estimated Ψ = 0.52-0.79 and Ψ = 0.10-0.32 where winter temperatures were coldest and warmest, respectively. Total forest loss was <1% during 1988-2011, and the loss of early-successional forest in the current and former range of Snowshoe Hares was similar as were mean patch size and a fragmentation metric of early-successional habitat. Thus, changes in forest characteristics did not explain the range contraction we observed. We used climate-model predictions and our occupancy model to predict that average occupancy probability across northern Pennsylvania may decline from 0.27 in 2004 to 0.10-0.18 by 2050-2059, depending on the climate model. The range of Snowshoe Hare in Pennsylvania has contracted to regions of Pennsylvania with the coldest winter temperatures and most persistent snowpack, and based on projected climate change, our results suggest further range contraction of Snowshoe Hare in Pennsylvania. [ABSTRACT FROM AUTHOR]

The effects of climate change on biodiversity have emerged as a dominant theme in conservation biology, possibly eclipsing concern over habitat loss in recent years. The extent to which this shifting focus has tracked the most eminent threats to biodiversity is not well documented. We investigated the mechanisms driving shifts in the southern range boundary of a forest and snow cover specialist, the snowshoe hare, to explore how its range boundary has responded to shifting rates of climate and land cover change over time. We found that although both forest and snow cover contributed to the historical range boundary, the current duration of snow cover best explains the most recent northward shift, while forest cover has declined in relative importance. In this respect, the southern range boundary of snowshoe hares has mirrored the focus of conservation research; first habitat loss and fragmentation was the stronger environmental constraint, but climate change has now become the main threat. Projections of future range shifts show that climate change, and associated snow cover loss, will continue to be the major driver of this species' range loss into the future. [ABSTRACT FROM AUTHOR]

Animals spend considerable time and energy acquiring food to meet their metabolic requirements, but if energetic or fitness costs are substantive, such as during winter, then some individuals may limit daily energy expenditure by reducing foraging duration. To date, the prevalence and magnitude of such compensatory foraging responses are poorly known. We examined energy balance compensation in free-ranging snowshoe hares ( Lepus americanus Erxleben, 1777) via a food supplementation experiment to determine whether individuals reduced their daily energy expenditure (DEE) and activity periods in response to increased food availability. Overall, food supplementation had no effect on diel activity patterns, although males had higher DEE compared with females. During early and mid-winter, hares did not alter their activity periods in response to food supplementation, but during late winter, when natural food availability declined, food-supplemented females (but not males) were ∼11% less active compared with controls. Natural food likely was sufficient and could have been acquired at relatively low energetic cost, but because males likely have higher DEE due to mating behavior whereas females may limit their activity (and thus DEE) to reduce predation risk, we conclude that gender-specific life-history demands can over-ride predicted responses to supplemental food when baseline food abundance is adequate. [ABSTRACT FROM AUTHOR]

Warming during the 20th century has changed the arctic landscape, including aspects of the hydrology, vegetation, permafrost, and glaciers, but effects on wildlife have been difficult to detect. The primary aim of this study is to examine the physical and biological processes contributing to the expanded riparian habitat and range of snowshoe hares (Lepus americanus) in northern Alaska. We explore linkages between components of the riparian ecosystem in Arctic Alaska since the 1960s, including seasonality of stream flow, air temperature, floodplain shrub habitat, and snowshoe hare distributions. Our analyses show that the peak discharge during spring snowmelt has occurred on average 3.4 days per decade earlier over the last 30 years and has contributed to a longer growing season in floodplain ecosystems. We use empirical correlations between cumulative summer warmth and riparian shrub height to reconstruct annual changes in shrub height from the 1960s to the present. The effects of longer and warmer growing seasons are estimated to have stimulated a 78% increase in the height of riparian shrubs. Earlier spring discharge and the estimated increase in riparian shrub height are consistent with observed riparian shrub expansion in the region. Our browsing measurements show that snowshoe hares require a mean riparian shrub height of at least 1.24-1.36 m, a threshold which our hindcasting indicates was met between 1964 and 1989. This generally coincides with observational evidence we present suggesting that snowshoe hares became established in 1977 or 1978. Warming and expanded shrub habitat is the most plausible reason for recent snowshoe hare establishment in Arctic Alaska. The establishment of snowshoe hares and other shrub herbivores in the Arctic in response to increasing shrub habitat is a contrasting terrestrial counterpart to the decline in marine mammals reliant on decreasing sea ice. [ABSTRACT FROM AUTHOR]

Survival and predation of snowshoe hares (Lepus americanus) has been widely studied, yet there has been little quantification of the changes in vulnerability of hares to specific predators that may result from seasonal changes in vegetation and cover. We investigated survival and causes of mortalities of snowshoe hares during the late increase, peak, and decline of a population in interior Alaska. From June 2008 to May 2012, we radio-tagged 288 adult and older juvenile hares in early successional and black spruce (Picea mariana) forests and, using known-fate methods in program MARK, evaluated 85 survival models that included variables for sex, age, and body condition of hares, as well as trapping site, month, season, year, snowfall, snow depth, and air temperature. We compared the models using Akaike’s information criterion with correction for small sample size. Model results indicated that month, capture site, and body condition were the most important variables in explaining survival rates. Survival was highest in July, and more generally during summer, when alternative prey was available to predators of hares. Low survival rates coincided with molting periods, breeding activity in the spring, and the introduction of juveniles to the sample population in the fall. We identified predation as the cause of mortality in 86% of hare deaths. When the source of predation could be determined, hares were killed more often by goshawks (Accipiter gentilis) than other predators in early successional forest (30%), and more often by lynx (Lynx canadensis) than other predators in black spruce forest (31%). Great horned owls (Bubo virginianus) and coyotes (Canis latrans) represented smaller proportions of hare predation, and non-predatory causes were a minor source (3%) of mortality. Because hares rely on vegetative cover for concealment from predators, we measured cover in predation sites and habitats that the hares occupied and concluded that habitat type had a greater influence on the sources of predation than the amount of cover in any given location within a habitat. Our observations illustrate the vulnerability of hares to predators in even the densest coniferous habitat available in the boreal forest, and indicate strong seasonal changes in the rates and sources of predation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Geophagy is thought to have several physiological benefits to animals, including mineral supplementation and adsorption of toxins. However, these benefits have rarely been demonstrated experimentally. Using soil from a known lick in northern Alaska, we investigated the effect of geophagy on food intake and mass loss in captive snowshoe hares ( Lepus americanus Erxleben, 1777) fed a formulated ration of feltleaf willow leaves ( Salix alaxensis (Andersson) Coville), a preferred forage of snowshoe hares. Lick soil contained 4.8% clay, 12.5% carbonates, and had more available Na (72.7 mg·kg−1) than willow leaves. Hares fed willow leaves consumed more soil (15.2 ± 2.0 g·kg-0.75·d−1) than those fed formulated ration (9.3 ± 1.3 g·kg-0.75·d−1). Hares had higher willow intake when offered soil (45.8 ± 2.0 g·kg-0.75·d−1) than those without soil (35.0 ± 2.1 g·kg-0.75·d−1), and willow-fed hares offered soil lost less body mass ( P < 0.001) than those without soil. Soil availability resulted in higher digestible intakes of N, Ca, Mg, Na, and K, but not P. These results suggest that the availability of mineral licks may alter forage use and functional response of this generalist herbivore in interior Alaska. [ABSTRACT FROM AUTHOR]

Snowshoe hares ( Lepus americanus Erxleben, 1777) fluctuate in 9-10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude. [ABSTRACT FROM AUTHOR]

The population dynamics of snowshoe hares ( Lepus americanus) are fundamental to the ecosystem dynamics of Canada's boreal forest. During the 8- to 11-year population cycle, hare densities can fluctuate up to 40-fold. Predators in this system (lynx, coyotes, great-horned owls) affect population numbers not only through direct mortality but also through sublethal effects. The chronic stress hypothesis posits that high predation risk during the decline severely stresses hares, leading to greater stress responses, heightened ability to mobilize cortisol and energy, and a poorer body condition. These effects may result in, or be mediated by, differential gene expression. We used an oligonucleotide microarray designed for a closely-related species, the European rabbit ( Oryctolagus cuniculus), to characterize differences in genome-wide hippocampal RNA transcript abundance in wild hares from the Yukon during peak and decline phases of a single cycle. A total of 106 genes were differentially regulated between phases. Array results were validated with quantitative real-time PCR, and mammalian protein sequence similarity was used to infer gene function. In comparison to hares from the peak, decline phase hares showed increased expression of genes involved in metabolic processes and hormone response, and decreased expression of immune response and blood cell formation genes. We found evidence for predation risk effects on the expression of genes whose putative functions correspond with physiological impacts known to be induced by predation risk in snowshoe hares. This study shows, for the first time, a link between changes in demography and alterations in neural RNA transcript abundance in a natural population. [ABSTRACT FROM AUTHOR]

Hybridization drives the evolutionary trajectory of many species or local populations, and assessing the geographic extent and genetic impact of interspecific gene flow may provide invaluable clues to understand population divergence or the adaptive relevance of admixture. In North America, hares ( Lepus spp.) are key species for ecosystem dynamics and their evolutionary history may have been affected by hybridization. Here we reconstructed the speciation history of the three most widespread hares in North America - the snowshoe hare ( Lepus americanus), the white-tailed jackrabbit ( L. townsendii) and the black-tailed jackrabbit ( L. californicus) - by analysing sequence variation at eight nuclear markers and one mitochondrial DNA (mt DNA) locus (6240 bp; 94 specimens). A multilocus-multispecies coalescent-based phylogeny suggests that L. americanus diverged ~2.7 Ma and that L. californicus and L. townsendii split more recently (~1.2 Ma). Within L. americanus, a deep history of cryptic divergence (~2.0 Ma) was inferred, which coincides with major speciation events in other North American species. While the isolation-with-migration model suggested that nuclear gene flow was generally rare or absent among species or major genetic groups, coalescent simulations of mt DNA divergence revealed historical mt DNA introgression from L. californicus into the Pacific Northwest populations of L. americanus. This finding marks a history of past reticulation between these species, which may have affected other parts of the genome and influence the adaptive potential of hares during climate change. [ABSTRACT FROM AUTHOR]

Snowshoe hares ( Lepus americanus Erxleben, 1777) are keystone herbivores supporting many boreal-forest predators. Understanding habitat use of hares can help predict how hares and their predators will be affected by disturbances such as climate change, which will have a particularly strong effect at tree line. We examined hare activity at arctic tree line near Churchill, Manitoba, using fecal pellet transects established in August 2012. We counted all hare fecal pellets at two plots per transect and measured plant abundance and vegetation structure surrounding the plots, then used model selection to determine the combinations of habitat features or plant species that best explained hare activity or presence. Hare pellets occurred at a higher density where tall shrub cover was high. Pellet density also increased with increasing canopy cover, tree size, tree density, visibility, and small shrub cover, but was negatively correlated with medium-sized shrub and herb cover. Hares preferred areas with willow (genus Salix L.) and avoided areas with unpalatable black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.). With climate warming, tree line is expected to advance northward and the increased tall shrub and willow cover predicted with increasing temperatures should benefit hares by providing greater predator protection and food. [ABSTRACT FROM AUTHOR]