DOI: 10.5061/dryad.z34tmpggs
title: Life history consequences of climate change in hibernating mammals: A review

description: Climatic shifts to warmer and often drier conditions are challenging
 terrestrial species worldwide. These shifts are occurring more rapidly at
 higher elevations and latitudes, likely causing disproportionate effects
 to mammalian hibernators there. While there is some information about how
 these species’ ranges are responding to climatic shifts, we lack an
 understanding of how climate components are affecting species’ life
 history variation, which is key to individual success and population-level
 resilience. We reviewed the literature to identify the direction of life
 history responses to climate change in mammalian hibernators along three
 axes: latitudinal, elevational, and temporal. We found 39 studies
 involving 27 species that reported climate effects on our four target life
 history traits – phenology, body mass/condition and growth, reproduction,
 and survival. We found warmer temperatures are advancing hibernator
 phenology and increasing reproductive success. By contrast, warming and
 drying trends are having uncertain effects on body condition, and complex
 effects on survival - depending on season, age class, latitude, and
 elevation. We found no pattern of significant climate-trait outcomes by
 duration or decade of study. More research on drought conditions -
 particularly in relation to resource availability - would help inform
 hibernator susceptibility to increased drying trends expected to intensify
 globally. Notably, our results are highly biased towards small mammal
 hibernators in Northern hemisphere alpine/mountain ecosystems, with few
 long-term studies conducted on Southern hemisphere hibernators.This review
 highlights that phenological shifts constitute one of the most obvious
 consequences of climate change, yet, the timing of life history events
 (e.g. timing of migration, reproduction, hibernation) remains poorly
 understood. Further integration of insights from physiologists,
 evolutionary biologists, and population ecologists working on wild
 populations will improve our collective understanding of the effects of
 seasonal climatic shifts on mammalian hibernator life history traits, key
 drivers of their population-level persistence.
description: We identified studies that addressed mammalian hibernator
 responses to anthropogenic climate change by conducting a standardized
 literature search in the ISI Web of Knowledge. Our final search took place
 on August 5th 2020 and identified studies published between 1950 and 2020.
 Searching for relevant studies with combinations of the following keywords
 - climat* AND hibern*, weather AND hibern* - generated a list of 717
 citations (see PRISMA flow diagram presented in fig. 1).      
             We qualitatively disregarded studies that addressed
 topics that were not in line with our review: those that reported on
 species that did not truly hibernate (i.e. animals that exhibit torpor
 bouts &lt; 24 hours, Geiser and Ruf 1995), or species that were not
 mammals. We further excluded studies where no statistics were reported,
 for which we could not find an English version, or that did not present
 sufficient evidence to detect a relationship between life history traits
 and climate or weather. We accepted experimental work if conducted in
 natura, but excluded studies that focused on habitat selection processes,
 activity budgets, and physiological correlates of hibernation, as opposed
 to the  traits of interest to our study: phenology, body mass/condition
 and growth, reproduction, and survival.             
 Once a working subset of studies was identified (N=39), we separated
 results based on the key life history traits of interest (phenology, body
 mass/condition and growth, reproduction, and survival) and collected the
 following information for each entry in our dataframe: the species common
 name, Latin name, Order, study type (qualitative, quantitative, or
 review), ecosystem (desert, forest, grassland, mountain/alpine,
 rainforest, savannah, tundra, or other), field site location, latitude,
 longitude, length of study, beginning year, end year, life history
 trait(s), season in which trait was measured (summer/active,
 winter/hibernation), age group measured (pup, yearling, adult),
 social/reproductive status (e.g. reproductive vs. non-reproductive,
 subordinate vs. dominant), general climatic driver(s) (i.e. drought index,
 global index, rain, snow, temperature), specific climatic driver(s) (e.g.
 July mean maximum temperature), direction of effect(s) (i.e. negative,
 positive, no effect), statistical method, statistics reported, sample
 size, and citation information (table S1). Because studies reported a
 variety of weather and climate variables, we conceptually standardized the
 results according to four expected future climatic conditions: warmer
 conditions, drier conditions, a longer growing season, and a shorter
 winter from earlier snowmelt. For instance, a positive effect of rainfall
 and negative effect of drought are conceptually the same result, so those
 would both be categorized here as negative effect of drier conditions.
  Each row summarized a unique result linking a specific life history trait
 and climatic driver(s); hence, studies with multiple results were
 represented multiple times in our dataframe and in our results.
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