The smallest terrestrial mammal, the Etruscan shrew (Suncus etruscus), has a neat trick to potentially save energy during the winter: It can shrink its brain, The Scientist reports. No heavier than a playing card, this mammal needs to eat eight times its bodyweight every day, and therefore cannot hibernate. Using MRI scans, researchers pinpointed this brain shrinkage to the somatosensory cortex, which processes sensory information from its whiskers. This area of the brain lost 28% of its volume in the winter, and regrew these neurons by the following summer, the researchers reported in the Proceedings of the National Academy of Sciences. The shrews’ brains shrunk even when the animals had unlimited food and no changes in their light and dark cycles in the lab. The phenomenon might therefore rely on internal cues as well as external ones, like a decrease in food availability.
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