Literature review protocol: Climate change and deer in boreal and temperate regions

Climate change causes far-reaching disruption in nature, where tolerance
thresholds already have been exceeded for some plants and animals. In the
short-term, deer may respond to climate through individual physiological
and behavioral responses. Over time, individual responses can aggregate to
the population level and ultimately lead to evolutionary adaptations. We
systematically reviewed literature (published 2000-2022) to summarize the
effect of temperature, rainfall, snow, combined measures (e.g., the North
Atlantic Oscillation) and extreme events, on deer species inhabiting
boreal and temperate forests in terms of their physiology, spatial use and
population dynamics. We targeted deer species which inhabit relevant
biomes in North America, Europe and Asia: moose, roe deer, elk, red deer,
sika deer, fallow deer, white-tailed deer, mule deer, caribou and
reindeer. Our review (218 papers) shows that many deer populations will
likely benefit in-part from warmer winters, but hotter and drier summers
may exceed their physiological tolerances. We found support for deer
expressing both morphological, physiological, and behavioral plasticity in
response to climate variability. For example, some deer species can limit
the effects of harsh weather conditions by modifying habitat use and daily
activity patterns, while the physiological responses of female deer can
lead to long-lasting effects on population dynamics. We identified 20
patterns, among which some illustrate antagonistic pathways, suggesting
that detrimental effects will cancel out some of the benefits of climate
change. Our findings highlight the influence of local variables (eg.
population density and predation) for how deer will respond to climatic
conditions. We identified several knowledge gaps, such as studies
regarding the potential impact on these animals of extreme weather events,
snow type and wetter autumns. The patterns we have identified in this
literature review should help managers understand how populations of deer
may be affected by regionally projected futures regarding temperature,
rainfall and snow.