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Why some animals are shrinking

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

Christophe Haubursin is a senior producer for the Vox video team. Since joining the team in 2016, he has produced for Vox’s YouTube channel and Emmy-nominated shows Glad You Asked and Explained.

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.

You can find this video and all of Vox’s videos on YouTube.

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