Sometimes, things pop up in places where we least expect them. So when an apex predator was sneaking through a saltmarsh where Brian Silliman was studying crabs and snails, he was shocked.

“I was being stalked by alligators,” says Silliman, a marine conservation biology professor at Duke University’s Nicholas School of the Environment. “Alligators are thought to be freshwater specialists. [Seeing one in a saltmarsh] just completely challenged everything I was taught about alligators.”

The encounter got Silliman thinking about other large animals cropping up in unlikely habitats. By combing through data from scientific studies and government reports, he found that large predators were being spotted in other ecosystems where they weren’t seen previously. (Related: “Why Do Whales Get So