Seasonal climate change and marmot demography

Abstract

Seasons strongly influence the life cycles of many species on Earth, and it is therefore not surprising that some of the best evidence we have of the ecological response to recent climate change comes from studies of phenology, the timing of seasonal events (1). We know, however, less about the demographic impacts of climate change within each season, how consistent those effects are across seasons and age groups, and if they could compensate or, on the contrary, amplify each other. Cordes et al. (2) provide a detailed analysis of seasonal demographic changes in an alpine mammal, the yellow-bellied marmot ( Marmota flaviventer ), which reveals the complexity of responses to climatic change. For example, increasing summer drought severity led to a decrease in pup and adult winter survival, whereas an increase in summer maximum temperatures and length of the growing season tended to increase yearling and adult summer survival. Overall, negative effects dominated across the multiple impacts of climate change, as the winter season is a critical bottleneck for these hibernating mammals. Nevertheless, the many pathways linking climate change and marmot demography and the uncertainty associated with projected seasonal climatic changes make predictions of the marmots’ future very uncertain. Integrating refined projections of seasonal climates and models of demographic changes such as Cordes et al. (2) do is an important challenge for future work. Cordes et al. (2) used 40 y (1979 to 2018) of high-quality, individual data collected at high-elevation (2,700 to 3,100 m above sea level) sites in Colorado. They used advanced capture–recapture statistical models to relate female survival within each season to environmental covariates measured at the same site. Overall, the observed climatic changes were consistent with expectations: decreasing total snowfall, earlier snowmelt date, increasing summer maximum temperatures, and more intense drought. One of the most striking potential ecological … [↵][1]1Email: Nigel.yoccoz{at}uit.no. [1]: #xref-corresp-1-1