Severin Hauenstein had a hunch. The biologist from Germany's University of Freiburg suspected that there was a link between the places where elephants in Tanzania were killed for their ivory and the visible presence of law enforcement.

He thought that the carcasses of poached elephants would generally cluster farther away from anti-poaching ranger posts. When he and his colleagues crunched the data for the once elephant-rich Ruaha-Rungwa ecosystem, they were surprised to find no correlation at all.

But then they took a closer look. For most ranger stations, the pattern was consistent with their expectations. But for others, they found the opposite: Carcasses were found quite close to ranger posts. That led to a second hunch—that the rangers stationed at those