The Juan Deriba killifish, found in a tiny area of Bolivia, jumps out of water to evade threats.

In the summer of 1996 in Central Bolivia, after a thunderstorm soaked the usually parched dry forest surrounding Juan Deriba Farm, 15-year-old Heinz Drawert strolled along one of the muddy forest trails. Out of the corner of his eye, he spotted something shimmering in a shallow puddle. He stopped to take a better look, and found himself staring at a tiny fish unlike any he had ever seen. Less than two inches long, it reminded him of the elaborate, sequined dresses of Carnival dancers: Its scales gleamed, dotted with red, green, and gold, and its flowing fins and tails were striped in vibrant bands of electric blue, crimson, and deeper carmine red. “Even then,” recalls Drawert, “I suspected that this could be a new species.”

For 25 years, Drawert, now a researcher at the Noel Kempff Mercado Museum of Natural History in nearby Santa Cruz de la Sierra, wondered about that fish.

“Life happened: I studied, built a career in science, and had a family, but the fish was always at the back of my mind,” he says. Then in 2021, the chance to search for the mysterious animal arrived when he joined a project recording freshwater species throughout Bolivia. Back into the forest Drawert went, retracing his steps along the muddy trails until he found another shimmering fish and began to document its unusual behavior. His fieldwork would eventually lead to a startling possibility: That this is a fish out of water by choice.

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