Is climate change really making squirrels sleep in?
- 09 Aug 2012, 17:00
- Freya Roberts and Verity Payne
Credit: Jeffrey Lane
Squirrels don't often form a central part of the climate debate,
and it might not be immediately obvious what a bushy-tailed rodent
living on the plains of the Rockies can tell us about climate
But a new paper about the Columbian Ground Squirrel offers an
interesting example of the challenges of linking local change up to
global trends. The
study suggests that over the past 20 years, these animals have
been emerging from hibernation later, leaving them less time to eat
The paper suggests climate change is having an effect on the
squirrels, linking their changing hibernation patterns to snow
melting later in the year, which seems to be because of an increase
in snowstorms towards the end of the snowy season - there was only
one snowstorm after mid-April during the first decade the study
considers, but seven in the second decade.
This, according to the authors, fits with climate projections that
suggest the atmosphere will be able to contain more moisture as it
warms, leading to more rain and snowfall. They say, citing the
IPCC's 2007 report (AR4):
"Specifically, an overall increase in
both total winter precipitation and the frequency of heavy
precipitation events is projected"
Still snowing outside
IPCC does suggest some regional predictions about snow and
"In southern Canada, precipitation is
likely to increase in winter and spring, but decrease in
Regarding snow cover, the IPCC suggests there will be shorter
snow seasons on a continental scale:
"Snow season length and snow depth are
very likely to decrease in most of North America..."
But as far as we can see, the IPCC report doesn't make any
predictions about whether the snow will fall later in this area of
the Rockies. So is the trend over the twenty year study period to
later snowfall really down to climate change? It's rather hard to
The snow season in southern Canada does seem to be getting
shorter. For example, a 2010
study comparing changes to snow seasons during the period
1989-2004 to the previous 16 years found that along the Rockies,
the duration of snow season has decreased by 5-10 days, and the end
of the snow season has got earlier by between 5-35 days. The paper
suggests this is an indication of climate change.
But in the study area specific to the Columbian Ground squirrels,
snow cover has persisted later in the year since 1992. And the
authors of the new squirrel study don't draw any conclusions about
whether the length of the snow season has changed over their
twenty-year study period.
This might raise a question about how confidently changes in
squirrel behaviour can be linked to climate change. Given that the
findings of this study are so localised, and the conclusions of the
IPCC are essentially on a continental scale, care should probably
It's also worth considering that these models project change over
the next 100-ish years, and don't really try to look at what sort
of change we are experiencing now.
Another cute animal picture? Surely not. Credit: Jeffrey
Hibernation is adaptation
Whatever the cause, the fact that these squirrels are emerging
later has consequences for their survival. The alpine conditions
these squirrels inhabit mean that they hibernate for 8-9 months of
the year, with only a short active period. As the squirrels emerge
later, they have less time to reproduce and eat. Without a big
enough fat store, they won't survive the following winter. The
authors noted that population growth is slowing.
While leading with headlines like
'Deadly lie-in for squirrels as climate change hits
hibernation' might be a step too far interpreting this study,
the research does add something to the climate debate. It reminds
us that within a bigger picture we should expect regional
variation, and that climate change might just alter the ecosystems
we occupy in unexpected ways.