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Why some animals are shrinking

Birds, mammals, and fish are miniaturizing as temperatures rise. Why?

Animals all across the world are undergoing a strange transformation. In Appalachia, salamander body sizes have decreased by 8 percent since 1960, menhaden fish caught in the Atlantic are 15 percent lighter than they were in 1987, and bird specimens at Chicago’s Field Museum have lost up to 4 percent of their body mass since collection began in the late 1970s.

A growing body of evidence suggests these changes are the product of global warming: As average temperatures rise, smaller bodies make it easier for warm-blooded animals to stay cool; for cold-blooded animals, warming temperatures speed up metabolism and stunt their growth.

These changes might appear relatively small, but they can have a huge impact on animals — making them more susceptible to predation, reduced offspring count, and drying out in droughts. Wild animals already face a wide range of threats; shrinking could push them even closer to extinction — with dire consequences for the ecosystems that humans rely on.

Read more about shrinking animals from Vox reporter Benji Jones.

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