Illustration by Daniel Horowitz for NPR

A lone emperor penguin makes his rounds, at the edge of an iceberg drift in the Antarctic's Ross Sea in 2006. John Weller/AP hide caption

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Jerky treats for dogs and cats have been linked to pet illnesses and deaths. But it's still unclear what is causing the problems. iStockphoto.com hide caption

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The changing landscape of of agriculture is leaving many sheep farms in the dust. Farms are larger and technology makes crops more economically attractive and sheep herds less. Luke Runyon/Harvest Public Meida/KUNC hide caption

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Anoushka Shankar's new album, Traces of You, comes out Tuesday. Harper Smith/Courtesy of the artist hide caption

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Most people associate the Nile with Egypt, but the river also flows through South Sudan, where much of it is bordered by jungle. That makes it a excellent destination for rafting and wildlife enthusiasts, says travel guide author Max Lovell-Hoare. Courtesy of Levison Wood/Secret Compass hide caption

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Clostridium difficile, a bacterium that causes severe diarrhea, can be difficult to treat with antibiotics. Stefan Hyman/University of Leicester hide caption

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An elephant in Kenya's Tsavo East National Park, home to some 13,000 of these remarkable animals. Ivan Lieman/AFP/Getty Images hide caption

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