Shrews Grow Their Noses 7% to Survive Winter Cold

Imagine if your nose grew bigger every winter to help keep you warm. That's exactly what Japanese shrews do, and scientists are calling it a delightful surprise.

Researchers studying 136 shrew skulls in Hokkaido, Japan, discovered something completely unexpected. While these tiny mammals shrink their brains by more than 20 percent during winter to conserve energy, their snouts actually grow 7 percent taller and 6 percent wider in the cold months.

"We realized something was off," says Yugo Ikeda, a mammalogist at Toyo University who led the study. The findings, published in the Proceedings of the Royal Society B, mark the first time scientists have seen this "reverse Dehnel's phenomenon" in shrews.

The brain shrinking part isn't new. Scientists have known since 1949 that small mammals like shrews, moles, and weasels temporarily reduce their organs during harsh winters and regrow them in spring. This helps them survive when food is scarce and temperatures plummet.

But why would a nose grow when everything else is shrinking? The research team has a compelling theory. A bigger nasal cavity creates more room for blood vessels that can warm freezing air before it reaches the brain.

"When the shrew inhales freezing air, this network efficiently warms it before it reaches the delicate, winter-shrunken brain," Ikeda explains. Think of it as a built-in heating system that protects their most vital organ during the coldest months.

The bigger schnozz might also help shrews sniff out food buried under deep snow or give them a stronger bite for tougher winter prey. However, researchers need more studies to confirm these additional benefits.

Why This Inspires

This discovery reminds us that nature constantly surprises us with creative solutions to survival challenges. These tiny shrews, living their short lives of less than two years, evolved an elegant system where one body part grows while others shrink to keep them alive through brutal winters.

The finding also highlights how much we still don't know about the natural world. Northeastern Asia hosts incredible shrew diversity, with more than 385 species worldwide, yet many remain understudied. Each new discovery opens doors to understanding how life adapts in remarkable ways.

Other scientists are already excited to explore whether shrews in milder climates show the same nose growth, which could reveal even more about how environment shapes evolution.

Nature's creativity in solving problems continues to amaze us, one tiny nose at a time.