Stressed out moms mean faster growing babies—if you’re a squirrel

Washington State

To give her offspring better odds in life, a mom can contribute all sorts of advantages: good genes, healthy milk, protection from predators, and more. Red squirrels—cousins of the more robust gray squirrels—are no exception. But new research in the journal Science shows that for these rodents, one such maternal boost stems from a surprising source: stress.

The research was conducted by a group of scientists who have spent the last 22 years studying a group of wild red squirrels in the Yukon. The ecosystem there follows an episodic pattern: every few years, when the spruce trees produce seeds en masse, the squirrel population booms in response. The team’s previous research had shown that in the years when squirrel numbers are especially high, fast-growing offspring tend to fare better than those that grow more slowly, presumably since they are better equipped to outcompete their rivals.

But how, exactly, do some squirrels end up growing so quickly?