For years, Roland Kays, a biologist at North Carolina State University, e-mailed fellow scientists for their camera trap images and saved them on his computer in a file of what he called “greatest hits.” His collection grew to more than 600 images from 150 researchers in 52 countries. Now they’re the centerpiece of Kays’s new book, “Candid Creatures,” which chronicles the use — and discoveries — of camera traps.

Things have come a long way since American photographer George Shiras first used camera traps to take photos of deer and other wildlife in the late 19th and early 20th centuries, some of which ended up in the pages of National Geographic.

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Shiras’s remote-controlled cameras were bulky and heavy, took only one photo at a time, and their flash was created by an explosion of magnesium powder, Kays said in an interview. Things got better when film came along, he said, but “you were limited to 36 pictures, and then you’d run out of film.”

Today’s digital cameras can store hundreds of images, and they stand up to heat, rain, animal nibbles and invasive insects. As Animalia wrote recently, their images led Georgia-based scientists to conclude that wild animals are spread throughout at least half of the Chernobyl Exclusion Zone. Kays said they also helped him discover in Panama that the seeds buried by small rodents called agoutis were frequently stolen by other rodents, then stolen back by agoutis.

“A picture tells a thousand words,” said Kays, who shared some of the images from the book. “Maybe a picture is worth a thousand data points, in this case.”

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Camera trap images have also helped tiger researchers, who can tell individual animals apart by their different stripe patterns, know more about the big cats’ small population and how much prey they need to survive, Kays said. “That’s been critical to tiger conservation,” he said.

Camera trap images confirmed that the giant sable antelope of Angola had survived that country’s long civil war. “That’s the most basic thing: Something is there, they’re still around,” Kays said.

Using camera traps, Kays and colleagues concluded that feral cats are rare in 32 protected areas, from South Carolina to Maryland. “That’s probably because there’s so many coyotes,” Kays said. “We’d get lots of pictures of coyotes, and probably one photo of a cat.”

“We definitely get predators with prey in their mouths, and I think that’s pretty cool,” Kays said.

Here are a few more photos from Kays’s book: