Conservation efforts need data. To understand how a species is faring, it’s essential to have information on roughly how many members of that species are living and where they’re living.

But this kind of information is fiendishly tricky and expensive to get. Wilderness areas cover huge tracts of land, large segments of which can be difficult or impossible to access. Methods to estimate population densities rely on expensive equipment and staff time, and conservation is desperately underfunded.

A paper in Current Biology this week proposes a cheap alternative that could work in certain contexts: tourist photos. Researchers found that data gathered from tourist images in Botswana provided comparable results to more traditional survey methods—and at a much lower cost.