Squirrels Feeling the Heat

Scientists say they are witnessing evolution in action in a population of North American red squirrels. The creatures are breeding earlier each year -- probably because of climate change.

Stan Boutin of the University of Alberta in Edmonton, Canada, and colleagues have spent nearly 15 years tagging and observing thousands of squirrels in the Canadian Yukon.

The scientists, in a study published Thursday in the online version of the Proceedings of the Royal Society of London, reported that the squirrels are now breeding an average of 18 days earlier in the spring than they did a decade ago.

This is probably because the region has warmed by several degrees over the last few decades because of global climate change.

The warming means there are more spruce cones to store away in the fall and that forests warm up sooner in the spring, making earlier breeding feasible and advantageous.

Part of the change can be attributed to squirrels’ altering their behavior from one year to the next.

But the scientists have found that genetic changes are taking place too.

Under warmer conditions, squirrels that are genetically apt to breed earlier have more reproductive success, leading to a steady increase in the trait among squirrels.

Andrew McAdam, a study coauthor, said the finding shows that species are being affected by global warming. At least for now, these squirrels are evolving to deal with the change.