Camera traps photos tell you what animals are in an area, but figuring out how many is tricky. E.g. two foxes in a photo doesn't mean there are only two; or a camera might see the same fox twice. But, knowing how many is key to answering questions like "Is the population of a species declining?" We're making a low-cost 3D vision add-on for camera traps. This is because 3D photos include spatial information, and existing mathematical models can use it to make much-needed population estimates.