Climate change is altering the physiology and phenology of an arctic hibernator

Climate warming is rapid in the Arctic, yet impacts to biological systems are unclear because few long-term studies linking biophysiological processes with environmental conditions exist for this data-poor region. In our study spanning 25 years in the Alaskan Arctic, we demonstrate that climate change is affecting the timing of freeze-thaw cycles in the active layer of permafrost soils and altering the physiology of arctic ground squirrels (Urocitellus parryii). Soil freeze has been delayed and, in response, arctic ground squirrels have delayed when they up-regulate heat production during torpor to prevent freezing. Further, the termination of hibernation in spring has advanced 4 days per decade in females but not males. Continued warming and phenological shifts will alter hibernation energetics, change the seasonal availability of this important prey species, and potentially disrupt intraspecific interactions., From 1996 to 2021, we deployed implantable abdominal temperature loggers and/or collar-mounted light and temperature loggers on free-living male and female arctic ground squirrels at two field sites (Atigun River Bridge 2 and Toolik Field Station) on the North Slope of Alaska, 254 km above the Arctic Circle. Detailed descriptions of field sites, devices, and device deployments are provided in the published literature (Sherriff et al., 2011; Williams et al., 2011, 2014, and 2016). Briefly, squirrels were captured using carrot-baited Tomahawk live-traps. From 1996–2016, squirrels were anesthetized and implanted with abdominal loggers using aseptic surgical technique. In more recent years (2014–2020), squirrels were fitted with collar-mounted light and temperature loggers. Devices were recovered using similar methods. Over this 25-year period, we collected biologging records representing 306 hibernation seasons from 199 adult individuals. We manually determined phenological events from bod...,