Anomalous snow events increase mortality for a winter-adapted species

Abstract

Winter is a costly time for animals, requiring individuals to adapt to increased energetic costs and reduced resources. Porcupines ( Erethizon dorsatum (Linnaeus, 1758)) confront winter by storing and catabolizing somatic stores. Increasing temperatures and attenuated snow conditions due to climate change increase porcupine survival, but impacts of greater weather variability have not been explored. In April of 2018, an anomalously heavy and late snowstorm occurred at our long-term study site in central Wisconsin followed by multiple mortalities among adult porcupines. We assessed cause of mortality and determined nutritional condition by extracting bone marrow and quantifying lipid content. Porcupines that died following the snow event had lower fat stores than the fall 2019 group and likely died of starvation. We estimated survival of female porcupines during the winters of 2012 and 2015–2018 to assess the effects of snow conditions and nutritional condition on survival. Survival declined with increased snow depth but increased with improved nutritional condition. The mass starvation event we observed in 2018 appeared to have resulted from deep snow increasing locomotive costs and reducing nutritional condition. As climate change increases the frequency of extreme weather events, including extreme snowfalls, we predict that the frequency of such clustered mortalities will increase.