Data from: Seasonal climate effects on the survival of a hibernating mammal

Global climate change and associated regional climate variability is
impacting the phenology of many species, ultimately altering individual
fitness and population dynamics. Yet, few studies have considered the
effects of pertinent seasonal climate variability on phenology and
fitness. Hibernators may be particularly susceptible to changes in
seasonal climate since they have a relatively short active season in which
to reproduce and gain enough mass to survive the following winter. To
understand whether and how seasonal climate variability may be affecting
hibernator fitness, we estimated survival from historical (1964-1968) and
contemporary (2014-2017) mark-recapture data collected from the same
population of Uinta ground squirrels (UGS, Urocitellus armatus), a
hibernator endemic to the western United States. Despite a locally warming
climate, the phenology of UGS did not change over time, yet
season-specific climatic variables were important in regulating survival
rates. Specifically, older age classes experienced lower survival when
winters or the following spring were warm, while juveniles benefited from
warmer winter temperatures. Although metabolic costs decrease with
decreasing temperature in the hibernacula, arousal costs increase with
decreasing temperature. Our results suggest that this trade-off is
experienced differently by immature and mature individuals. We also
observed an increase in population density during that time period,
suggesting resources are less limited today than they used to be.
Cheatgrass is now dominating the study site and may provide a better food
source to UGS than native plants did historically.