Tip-toeing tapirs. Curious chimpanzees. Even peering poachers. All took pictures of themselves in what scientists are calling the first global survey of tropical mammals with camera traps.

Led by Conservation International, the $500,000 study analyzed 52,000 photos snapped by 420 automatic cameras in seven countries. The images confirm a long-standing notion in the conservation community: The larger a nature preserve, the more diverse and numerous its mammals.

“These animals are difficult to study, in remote places, and elusive, rare,” said Jorge Ahumada, the ecologist who led the new study published in the Philosophical Transactions of the Royal Society B. “We use camera traps as census workers to help us witness what was happening.”

In the Bwindi Impenetrable National Park in Uganda - best-known for its gorillas and chimpanzees - the traps captured a low-slung honey badger, never before seen there. Another photo shows a suspected poacher, carrying a spear and a machete, walking a trail. In the next shot, the man’s face peers into the camera.

Deployment of motion-triggered cameras by scientists has exploded since the late 1990s, according to a 2008 report. Mounted low on trees, the textbook-sized camera boxes - often outfitted with infrared flashes to minimize night-time disruptions - have captured new-to-science species and directed conservationists toward hidden populations.

Lack of information on the number and variety of tropical mammals hinders conservation efforts, Ahumada said. The International Union for Conservation of Nature reports that for 15 percent of all mammal species, too little data exists to know whether they are endangered. Ahuamada said the trove of camera-trap data will help fill that gap.

The ongoing project has expanded to 17 countries, with a goal of eventually reaching 40.