Shrew Snouts Grow in Winter, Study Finds

In a remarkable display of adaptation, long-clawed shrews from Japan have demonstrated a unique response to winter's chill. While many of their skull components shrink, their snouts notably expand. This biological process, termed 'reverse Dehnel's phenomenon,' involves a physical alteration of the bone structure in the rostrum, or snout.

Researchers observed that shrew brain cases were significantly smaller in winter specimens compared to younger shrews. However, the height and width of the snout increased, creating a larger nasal cavity. This change is hypothesized to help regulate body temperature by warming inhaled frigid air before it reaches the brain.

Additionally, the expanded nasal cavity may enhance the shrew's ability to detect prey, such as earthworms, during the lean winter months. These seasonal modifications are reversible, with shrew measurements returning to larger sizes in warmer seasons. Future research aims to explore similar phenomena in other shrew species.