In the cold months, nature sometimes surprises us with unexpected solutions. Scientists have discovered that in long-clawed shrews from Japan, the nasal part of the skull noticeably increases in winter, even though the rest of the skull, including the braincase, shrinks.
The study, published in the journal Proceedings of the Royal Society B, is based on an analysis of 136 skulls collected in Hokkaido from 1948 to 1988. In winter, the height of the braincase decreased by 12 percent compared to young individuals collected in summer and autumn. At the same time, the height of the nasal part (rostrum) increased by 7 percent, and the width by 6 percent.
This phenomenon has been called the "reverse Dehnel's phenomenon"—in contrast to the well-known seasonal reduction of the body and brain in many shrews. The changes are reversible: in spring and summer, the dimensions return to their previous values. Researchers suggest that the expanded nasal cavity helps warm the icy air before it reaches the shrunken brain, thanks to a dense network of blood vessels.
An additional advantage may be an improved sense of smell, allowing them to find prey, such as earthworms, in conditions of scarce winter food. Mechanical strengthening of the nose for processing tougher food has not yet received convincing confirmation.
The discovery highlights how flexibly mammals adapt to seasonal challenges. Similar changes may also occur in other shrew species in Hokkaido, and scientists plan to continue their research.
Observations of such adaptations remind us how important it is to preserve natural habitats where animals can exhibit their unique survival strategies.
