Milder winters appear to have resulted in physical changes in two species of mice in southern Quebec, in what the lead researcher from McGill University says is "very likely" an example of the consequences of climate change.

For the past decade, biologist Virginie Millien has been studying two species — the white-footed mouse and the deer mouse — in Mont Saint-Hilaire at McGill's Gault Nature Reserve, about 40 kilometres east of Montreal. 

By comparing their own research to data collected as far back as the 1950s, Millien and her team discovered that the skull shapes of both mouse species have changed over time.

"This is a real-life experiment," said Millien, whose work was published recently in the journal Evolutionary Ecology.

The changes were more pronounced in the white-footed mouse, but in both cases the cranial shapes of the two species have become more distinct.

The white-footed mouse — which is a carrier of lyme disease — has also been moving farther north as winters get milder, at a rate of around 11 kilometres a year, the researchers estimate.

Millien said the changes may be related to a dietary shift caused by climate change, combined with competition for food resources between the two species of mice.

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One question that remains, she said, is whether the changes are genetic and will be passed on to future generations (evolution) or whether they represent what's known as "plasticity," defined as the capacity of some species to adjust to rapid environmental change.

Millien said the findings add to a small but growing body of research documenting cases of rapid response by wildlife to climate change.

Mice are an ideal subject, she said, given their quick regeneration rate. But humans are also likely to change in response to climate change, she said.

"There's no reason why we should not evolve," she said.