Do Any Animals Shrink When the Seasons Change?

It turns out that the common shrew is pretty shrewd. In a study published in the journal Current Biology in October 2017, researchers reported that the size of the tiny mole-like animal’s braincase shrinks by almost 20 percent in preparation for winter. Then, as spring approaches, its skull expands, almost reaching its original size. In fact, shrews lose significant overall body mass -- including the size of their brains, organs, and spines -- in order to conserve energy and limit food requirements as the cold season approaches.

When size matters:

  • The scientists studied shrews of all ages to make sure that the shrinkage was seasonally triggered, rather than just being a function of age.
  • In the 1940s, Polish zoologist August Dehnel reported on the unusual braincase shrinkage, now called the Dehnel phenomenon. The new research clarifies the extent of the morphing.
  • Shrews are found all around the world, and they are among nature’s few venomous mammals. They are known for their ferocity, earning the nickname “tigers of the small animal world.”
More Info: Smithsonian magazine

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