Veterinarian Vint Virga says that animals in zoos, like this lion, need to have a bit of control over their environment. iStockphoto hide caption

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Arturo, the only polar bear in Argentina, lives in captivity at a zoo in Mendoza. The plight of the "sad bear" has spawned more than 400,000 signatures on a petition to get him moved to a "better life" in Canada. AFP/Getty Images hide caption

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A curious cuttlefish stares back at the camera from inside The Smithsonian's National Zoo Invertebrate Exhibit. The exhibit, home to dozens of small aquatic and terrestrial species without backbones, closed on Sunday. Meghan Murphy/Smithsonian's National Zoo hide caption

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After several news outlets reported that a man dressed as a gorilla was shot with a tranquilizer gun, a zoo in Tenerife, Spain, wants to be clear: There was no gorilla suit involved. Richard Thomas/iStockphoto hide caption

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The lions at the Copenhagen Zoo eat the remains of a healthy young giraffe named Marius in February. It's unclear whether the lion pictured was one of those euthanized. Kasper Palsnov/AFP/Getty Images hide caption

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A security guard closes the gate at the Pittsburgh Zoo, where a 2-year-old boy was killed Sunday. John Heller/AP hide caption

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