Wildfire is the most impactful disturbance regime in the North American boreal region, driving the structure and composition of forests across the region. Recent climate models predict that increasing fire intensity and frequency will result in a shift from a largely coniferous forest to one with a greater dominance by deciduous species. We investigated how an iconic predator of the boreal system, the Canada lynx ( Lynx canadensis ), moves through a range of burn scars (4–73 years old). Using GPS collars at 4‐h fix rates, we fitted integrated step selection models to lynx movements across an 80‐year post‐fire chronosequence to assess habitat selection in both deciduous and coniferous forests. We predicted that lynx would primarily select intermediately aged spruce and young deciduous stands, mirroring previous research on the habitat selection of their main prey, snowshoe hares ( Lepus americanus ). We found, however, that lynx habitat selection peaked at intermediately aged stands in both forest types, with selection for younger deciduous stands in the winter months. There was no seasonal change in coniferous stands as they experience little change in cover across seasons. We hypothesize that lynx select for habitats that maximize capture probability as opposed to simply habitats with the highest hare density. Together, these results show that lynx can be resilient to short‐term shifts toward intermediate‐aged stands. However, these benefits will likely diminish in the longer term as the decrease in fire return interval may reduce the prevalence of intermediate‐aged stands.

Connectivity is determined by the degree to which inhospitable habitat matrices are permeable to gene flow. Successful gene flow requires that dispersing individuals travel to new populations, survive there, and finally, reproduce. Consequently, examinations of connectivity must consider both the permeability of the landscape and individual survival patterns, as surviving individuals are the only ones that have the potential to reproduce. We investigated functional connectivity of Canada lynx (Lynx canadensis) populations in the northwestern boreal forest using an unprecedented dataset of 207,957 relocations from 142 individual lynx. As a specialist predator of snowshoe hare (Lepus americanus), lynx populations follow a 10- to 12-year population cycle, which lags a few years behind the population cycles of hares. We used integrated step selection analyses to quantify habitat selection, and Bayesian counting process implementation of wrapped Cauchy survival models to evaluate mortality risk during dispersal. We compared movement patterns and survival across behavioral states and population phases, following the a population decline. Our results showed few complete physical barriers to dispersal in the study region, with many lynx dispersing greater than 3000 km. Step-selection analysis of lynx movement revealed a higher tolerance for poor quality habitats in dispersing lynx as compared to resident lynx, primarily in selection for rugged terrain and closer proximity to roads. These differences resulted in a higher estimate of landscape permeability for dispersing lynx compared to residents. When survival patterns were considered, there were increasingly stark differences between resident and dispersing lynx during population declines. Dispersing lynx faced markedly lower survival rates than resident lynx. Overall, this paints a picture of a more connected landscape during population highs, which becomes increasingly fragmented during population lows. Canada lynx populations appeared to have few impermeable barriers across the landscape, but they face periods of low functional connectivity driven by lower survival during population declines. This emphasizes the significance of maintaining high-quality refugia habitats from which population rebounds can occur following cyclic lows.

Wildfire is the most important disturbance regime in North American boreal forest communities, driving forest composition and structure across this region. Recent climate models predict that increasing fire intensity and frequency will result in a shift from a largely coniferous forest to one with a greater dominance by deciduous species. We investigated how an iconic predator of the boreal system, the Canada lynx (Lynx canadensis), moves through a range of burn scars (2-78 years old) and if these movements reflect habitat selection of their main prey, the snowshoe hare (Lepus americanus). Using GPS collars at 4-h fix rates, we fitted integrated step selection models to lynx movements across an 80-year post-fire chronosequence to assess habitat selection in both deciduous and coniferous forests. We predicted that lynx would primarily select intermediately-aged spruce, but young deciduous stands, mirroring the habitat selection of snowshoe hares. We found, however, that lynx habitat selection peaked at intermediately aged stands in both forest types. We hypothesize that this difference is driven by selection for habitats that maximize capture probability as opposed to simply representing the highest hare density. This idea is supported by observed seasonal changes in peak selection in deciduous stands, with selection for younger stands in winter, when leaf loss reduces cover. There was no seasonal change in coniferous stands as they experience little change in cover across seasons. Together these results show that lynx can be resilient to short-term shifts toward intermediate-aged stands. However, these benefits will likely diminish in the longer term as the decrease in fire return interval may reduce the prevalence of intermediate-age stands.

Cyclical population dynamics are a common phenomenon in populations worldwide, yet the spatial organization of these cycles remains poorly understood. In this study, we investigated the spatial form and timing of a population collapse from 2018 to 2022 in Canada lynx (Lynx canadensis) across the northwest boreal forest. We analyzed survival, reproduction, and dispersal data from 143 individual global positioning system (GPS) collared lynx from populations across five study sites spanning interior Alaska to determine whether lynx displayed characteristics of a population wave following a concurrent wave in snowshoe hare (Lepus americanus) abundance. Reproductive rates declined across the study sites; however, site-level reproduction declined first in our easternmost study sites, supporting the idea of a population wave. Despite a clear increase in percent of dispersing lynx, there was no evidence of directional bias in dispersal following a hare population wave. Analysis did show increasingly poor survival for lynx dispersing to the east compared to combined resident and westward dispersal. This pattern is consistent with a survival-mediated population wave in lynx as the driver of the theorized population wave. The combination of these factors supports the idea of a hierarchical response to snowshoe hare population declines with a drop in lynx reproduction followed by increased dispersal, and finally reduced survival. All of this evidence is consistent with the expected characteristics of a population undergoing a traveling wave and supports the hypothesis that lynx presence may facilitate and mirror the underlying wave patterns in snowshoe hare.

The relationship between body size and latitude has been the focus of dozens of studies across many species. However, results of testing Bergmann’s rule — that organisms in colder climates or at higher latitudes possess larger body sizes — have been inconsistent across studies. We investigated whether snowshoe hares (Lepus americanus Erxleben, 1777) follow Bergmann’s rule by investigating differences in body mass using data from six published studies and from data of 755 individual hares captured from 10 populations across North America covering 26° of north latitude. We also explored alternative hypotheses related to variation in hare body mass, including winter severity, length of growing season, elevation, and snow depth. We found body mass of hares varied throughout their range, but the drivers of body mass differed based on geographic location. In northern populations, females followed Bergmann’s rule, whereas males did not. In northern populations, male mass was related to mean snow depth. In contrast, in southern populations, body mass of both sexes was related to length of the growing season. These differences likely represent variation in the drivers of selection. Specifically, in the north, a large body size is beneficial to conserve heat because of low winter temperatures, whereas in the south, it is likely due to increased food supply associated with longer growing seasons.

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.

Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9-10 year cycles throughout much of their North American range. Regional synchrony has been assumed to be the rule for these cycles, so that hare populations in virtually all of northwestern North America have been assumed to be in phase. We gathered qualitative and quantitative data on hare numbers and fur returns of Canada lynx (Lynx canadensis Kerr, 1792) in the boreal forest regions of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe synchrony in the time window of 1970-2012. Broad-scale synchrony in lynx fur returns was strong from 1970 to about 1995 but then seemed to break down in different parts of this region. Hare populations at 20 sites in Alaska, the Yukon, and Northwest Territories showed peak populations that lagged by 1-4 years during the 1990s and 2000s cycles. The simplest hypothesis to explain these patterns of asynchrony in hare cycles is the movement of predators from British Columbia north into the Yukon and then east into the Northwest Territories and west into Alaska. A traveling wave of these cycles is clearly seen in the lynx fur returns from western Canada and Alaska from 1970 to 2009. One consequence of a failure of synchrony is that hare predators like Canada lynx and Great-horned Owls (Bubo virginianus (Gmelin, 1788)) can move from one adjacent area to the next within this region and survive long enough to prolong low densities in hare populations that have declined earlier.

Snowshoe hares (Lepus americanus) are a primary prey species for Canada lynx (Lynx canadensis) in western North America. Lynx management plans require knowledge of potential prey distribution and abundance in the western United States. Whether even-aged regenerating forests or multi-storied forests contain more snowshoe hares is currently unknown. During 20062008, we estimated snowshoe hare density in 3 classes of 3070-year-old lodgepole pine (Pinus contorta) and 4 classes of late seral multi-storied forest with a spruce (Picea engelmannii)-fir (Abies lasiocarpa) component in the Bridger-Teton National Forest, Wyoming. We recorded physiographic variables and forest structure characteristics to understand how these factors influence abundance of snowshoe hares. In many instances, snowshoe hares were more abundant in late seral multi-storied forests than regenerating even-aged forests. Forest attributes predicting hare abundance were often more prevalent in multi-storied forests. Late seral multi-storied forests with a sprucefir component and dense horizontal cover, as well as 3070-year-old lodgepole pine with high stem density, were disproportionately influential in explaining snowshoe hare densities in western Wyoming. In order to promote improved habitat conditions for snowshoe hares in this region, management agencies should consider shifting their focus towards maintaining, enhancing, and promoting multi-storied forests with dense horizontal cover, as well as developing 3070-year-old lodgepole pine stands with high stem density that structurally mimic multi-storied forests. (c) 2012 The Wildlife Society.

Snowshoe hares (Lepus americanus) are an important prey species for Canada lynx (Lynx canadensis) and are considered critical for lynx population persistence. Determination of snowshoe hare distribution and abundance is needed by land management agencies for lynx conservation. An accepted approach for estimating snowshoe hare abundance is the use of fecal-pellet plot counts. Locally derived regression equations are preferred for accurate calibration of pellet counts to snowshoe hare density due to local differences in pellet deposition and decomposition. We used linear regression to examine correlations between snowshoe hare density, as determined by mark-recapture estimates, and pellet plot counts on both uncleared plots and annually cleared plots on the Bridger-Teton National Forest, western Wyoming, USA. We found significant correlations between snowshoe hare density estimates and fecal pellet counts for both uncleared and annually cleared pellet counts; however, the relationship was stronger (higher r) when using pellet counts from annually cleared plots. In addition, we found that adjusting the buffer size by omitting hard habitat edges (not used by hares) around trapping grids improved correlations between snowshoe hare density and fecal pellet counts for both uncleared plots and annually cleared plots. Though precision is sacrificed when using uncleared plots, they may be useful as a coarse index of habitat use by snowshoe hares. Our derived regression equations may be useful to identify important foraging habitat for Canada lynx in western Wyoming. Land managers responsible for conserving snowshoe hare habitat in western Wyoming may use these equations to monitor changes in hare populations among habitats and during prescribed management actions.