Climate change is altering interspecific interactions globally, yet community-level responses are difficult to predict due to both the direct and indirect effects of changing abiotic and biotic conditions. Snowshoe hares (Lepus americanus) are particularly vulnerable to decreasing snow cover and resultant camouflage mismatch. This species shares a suite of predators with alternative prey species including porcupines (Erethizon dorsatum) and ruffed grouse (Bonasa umbellus), and all three species historically exhibited synchronized population dynamics. Recently, the community has become partially disassembled, notably with the loss of snowshoe hares and associated enemy-mediated indirect interactions resulting from declining snow duration. Specifically, we hypothesized that the extirpation of hares in the early 1990s indirectly increased predation pressure on ruffed grouse and porcupines. To test our hypothesis, we experimentally translocated 96 snowshoe hares to a site within a regional ecotone between northern and southern forests where snowshoe hares were recently extirpated and monitored community members before, during and after translocation. Ruffed grouse were only loosely associated with the biotic interactions that linked porcupines and snowshoe hares, likely due to predation occurring from avian predators and strong negative direct effects of declining winter snow depths. In contrast, predation of neonate porcupines was virtually non-existent following repatriation, compared to periods without hares. This abrupt attenuation of predation did not increase overall survival due to increased non-predation mortality from cold, early spring weather. Porcupines directly benefitted from warming winters: decreased snow cover increased adult survival and warmer temperatures around parturition increased maternal condition and reduced non-predation causes of mortality for neonates. Our experimental manipulation suggests that enemy-mediated indirect interactions were likely important features of this community; however, climate change has disrupted these interactions, resulting in extirpation of a central prey species (snowshoe hare) and increased predation of an alternative prey species (porcupine). We show complex effects from climate change with some species directly and negatively affected, while others benefitted from direct effects of warming winters, but suffered negative effects from indirect interactions. Absent snowshoe hares and associated biotic interactions, continued persistence of this community module is unlikely, potentially resulting in altered no-analogue communities along trailing edge distributions.

Data were collected on Porcupine (Erethizon dorsatum) and ruffed grouse (Bonasa umbellus) at Sandhill Wildlife Area in central Wisconsin between 1968 and 2018. Census data on porcupine was collected annually between 1968 and 2018 (Wilsonetal_Grouse_Porcupine_Counts). Survival data for adult, subadult and juvenile porcupines was collected annually between 1997 and 2018 (Wilsonetal_CJS). Survival data for grouse was collected between 2016 and 2018 (Wilsonetal_Grouse_KnownFate). Cause-specific mortality data on neonate porcupines was collected between 2015 and 2018 (Wilsonetal_NPCIF & Wilsonetal_CPH). Cause-specific risk factor data was Metrics of maternal condition were generated using capture data on pregnant females (Wilsonetal_Res1), and posthoc analysis of predictors of maternal condition were performed using climatic and seasonal data (Wilsonetal_MaternalCondition).

Details on files and variables used in analysis are listed in the README file