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Throughout forests and prairies in Sumatra and Kenya, rare animals, such as and leopards, are shot regularly—not with guns, but with cameras. Scientists have hidden motion-activated cameras to capture animals that pass by in an effort to help document diversity, population size, and distribution of a region’s wildlife, information that’s invaluable in conserving species.

 

The image have been compiled into the Wildlife Picture Index, a collection of photo albums that can each hold thousands of photos of dozens of species from a given area. The and the Zoological Society of London created the index.
 

Rhino. Courtesy Wildlife Conservation Society
 
The method has already aided scientists in detecting population declines. For instance, analyzing some 5,450 shots of tigers, rhinos, Asian elephants, and 22 other mammals in Sumatra’s Bukit Barisan Selatan National Park, researchers found a 36 percent net drop in the park’s biodiversity (likely largely due to , though activities like also take a toll).

 

"The Wildlife Picture Index is an effective tool in monitoring trends in wildlife diversity that previously could only be roughly estimated,” WCS’s Tim O’Brien said in a . “We expect that the Wildlife Picture Index can be implemented and maintained at a relatively low cost per species monitored and provide important insights into the fate of rainforest and savannah biodiversity."

 

Here’s a sample of photos in the Wildlife Picture Index.
 

Asian elephants. Courtesy Wildlife Conservation Society
 

Lion. Courtesy Wildlife Conservation Society
 

Aardvark. Courtesy Wildlife Conservation Society
 

Steinbok. Courtesy Wildlife Conservation Society
 

Caracal and kittens. Courtesy Wildlife Conservation Society
 

Aardwolf. Courtesy Wildlife Conservation Society
 

Leopard. Courtesy Wildlife Conservation Society
 

Spotted hyena. Courtesy Wildlife Conservation Society