Study finds that mild winters are detrimental to butterflies

April 20, 2012
Study finds that mild winters are detrimental to butterflies

The recent mild winter throughout much of the United States was a cause for celebration for many. However, butterfly aficionados shouldn't be joining in the celebration.

A new study by Jessica Hellmann, associate professor of biological sciences at the University of Notre Dame, and researchers from Western University found that mild winters, such as the one many of us just experienced, can be taxing for some butterfly or possibly other species.

Hellmann and her fellow researchers studied caterpillars of the Propertius Duskywing butterfly, which feed on Gary . This species of caterpillar, like many insects, has a higher and burns more fat during mild winters.

"The energy reserves the caterpillars collect in the summer need to provide enough energy for both overwintering and metamorphosing into a butterfly in the spring," Caroline William, lead author of the study, said.

So a butterfly needs to conserve as much energy as it can during the winter months. In the paper, Hellmann and her colleagues explain for the first time how warmer winters can lead to a decrease in the number of .

However, Hellmann and the Western University researchers found that warmer winters might not always reduce as much as one might initially think. They reared caterpillars in two different locations: one which often experiences more variable and warmer and one which generally features more stable and generally cooler winter temperatures. The caterpillars that were exposed to the warmer and more variable conditions were better able to withstand the warmer conditions, simply by being exposed to them. They did so by lowering the sensitivity of their .

However, the ability of even caterpillars accustomed to warmer, more variable winters to cope with such conditions is still limited, according to the researchers. They calculated the energy use of both groups of caterpillars and discovered that the caterpillars that lower their metabolic rates to deal with warmer winters still use significantly more energy to survive them.

"We still have lot to learn about how organisms will respond to climate change," Hellmann said. "Our study shows significant biological effects of climate change, but it also shows that organisms can partially adjust their physiology to compensate. We now need to discover if other species adjust in similar ways to our example species."

So although mild winters may be a cause for celebration for many of us, those who are concerned are biodiversity might find them to be much more somber seasons.

Explore further: Warm winters may be nice for humans but not so much for butterflies

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1.6 / 5 (7) Apr 20, 2012
Commonsense suggests that mild winters would require less not more metabolic outlay than colder ones so how come "this species of caterpillar, like many insects, has a higher metabolic rate and burns more fat during mild winters." I can think of lots of reasons why mild winter might affect butterfly survival--it might allow more predators to survive, for example--but extra energy expenditure is not one of them.

On reading the paper (open access) I see it is not mildness but variability (due to Jensen's inequality) that increases metabolism and this is the problem. The press release does not explain this very well.

1.4 / 5 (10) Apr 20, 2012
"mild winters, such as the one many of us just experienced"

Tell that lie to the families of the 1000 or more people who froze to death in Europe this winter.

Jan 2011 and Jan 2012 were colder than January in 1942 and 1944.

1.6 / 5 (7) Apr 20, 2012
I agree, far more people have died to the cold than the heat, throughout history.
not rated yet Apr 20, 2012
I can understand this "warmer = faster metabolism". Cold blooded animals have this property. Cells internal metabolism, like many chemical reactions, happen the faster the warmer the environment is. Warm blooded animals can control their metabolism rate by keeping their temperature stable, but cold blooded have no such control, so their energy expenditure is tied to ambient temperatures. Some hibernating warm blooded animals use this coping mechanism too to lower their temperature and therefore metabolism rate during winter, when they could not find enough feed. Bats are one example of them.
not rated yet Apr 20, 2012
"mild winters, such as the one many of us just experienced"

Tell that lie to the families of the 1000 or more people who froze to death in Europe this winter.

I guess you failed to see the word, "many". They did not use the word "all", not even "the majority", just "many".

I think some 300 million people qualify for the word "many".
For, while Europe had a record breaking winter for cold and snow, the opposite was true in the US. They are looking into the correlation to see if there might be a link...

1.3 / 5 (10) Apr 20, 2012

I think some 300 million people qualify for the word "many".

Just because on small region of the US was warm doesn't mean it all was.

In the Northwest, the most recent 6 month period was ranked 68th out of 117.


The West was ranked 75 out of 117.


It was damn cold in Alaska too.

1.4 / 5 (10) Apr 20, 2012
Interestingly enough, in the West March was 7.6F colder than March of 1934.

In the Northwest, March 2012 was 7F colder than March of 1934.

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