Winter strategy helps explain why northern mammals are not all shrinking with warming
WHAT THE EVIDENCE SAYS
Researchers used roughly five decades of body-mass data from three northern mammals with contrasting overwintering strategies. Snowshoe hares, exposed above the snowpack, declined in body mass and responded negatively to temperature and snow. Deer mice showed no long-term body-mass trend but increased with growing-degree days, while red-backed voles increased with temperature and snow. The authors argue that winter ecology mediates which climate mechanism dominates.
WHY IT MATTERS / OUR READ
Body-size responses to warming are not a simple temperature rule. Natural history determines what climate exposure an animal actually experiences, so models that ignore subnivean refuge, snow conditions or seasonal strategy can average together opposite responses.
CAVEATS / UNCERTAINTY
Only three species in one rapidly warming northern region were examined, and body mass is not a direct fitness measure. Long-term observational relationships can reflect correlated ecological change, and results should not be generalized to all mammals or used as a universal body-size law.
SOURCE
Global Change Biology — primary study
View original evidence ↗
Nearly 50 years of Yukon data show snowshoe hares lost body mass while two subnivean rodents showed different or opposite trends—natural history changed the climate response.
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