CU-Boulder study shows differences in mammals responding to climate change
Jan. 21, 2014 Christy McCain
If you were a shrew snuffling around in a North American forest, you would be
27 times less likely to respond to climate change than if you were a moose.
That is just one of the findings of a new CU- Boulder study led by Assistant
Professor Christy McCain that looked at how 73 different North American mammal species are responding -- or not responding -- to climate change.
CUT 1 “The two traits that were most related to who responded, the largest predictor, was body size. If you are really big - something like a big horned sheep, a reindeer, a polar bear, but even medium-sized mammals - those are almost responding 100 percent at the time. (:18) Whereas if you’re really little - a shrew which weighs anywhere between 2 and 10 grams to smaller rodents under 100 grams - they’re almost not responding at all to climate change.” (:31)
McCain, who is a biologist in CU-Boulder’s ecology and evolutionary biology department, and her research team looked at more than 1,000 different scientific studies on North American mammal responses to human-caused climate change, eventually selecting 140 papers as the basis for the study. From those papers they broke them down into two types of studies.
CUT 2 “One they had historical data that had been collected maybe in the 1920s to
1940s and then the researchers went back to those places and re-assessed whether the mammals were still there or whether they had locally gone extinct or whether they had been reduced in numbers or whether they had shifted their ranges. (:22) The other type of study was ones that they had studied a population over a really long time period - a time period where they started before climate change - and then way after the period in the 80s where we started documenting climate change into now.” (:37)
McCain says one of the most intriguing findings was that some small mammals may find shelter to climate change by using a wider array of “micro-climates” available in the vegetation and soil. She compared the findings with the events at the K-T boundary 66 million years ago when an asteroid smacked Earth, drastically changing the climate and killing off the big dinosaurs but sparing many of the small mammals.
CUT 3 “There’s this hypothesis about climate sheltering where research had surmised that the smallest mammals made it through the KT boundary - this huge change in climate that happened really quickly – because they were small and nocturnal and living underground. (:18) Where many of these really big things that were dominating the
Earth, dinosaurs, went extinct.” (:24)

McCain says something that’s important for the public to understand is the fact that it’s the largest mammals responding most to climate change – the mammals many people find the most charismatic in the animal world.
CUT 4 “The things that are responding most to climate change are the things that we tend to like the most, right, that we go to parks to see - big horned sheep and elk and reindeer and polar bears. (:13) And it’s important to think about because if the things we like the most are the things that are responding the most to climate change they’re also the things that have the highest extinction risk. That should be a motivation for us to respond by doing more to alleviate the effects of climate change.” (:30)
McCain says her current studies will look at how temperature influences food supplies and how that influences populations and the numbers of individual species.
-CU-