Scientists figured out a new way of quantifying wildlife populations in Indonesia, thanks to strategically placed motion-triggered camera traps.

Tim O'Brien of the Wildlife Conservation Society and his team, used the Wildlife Picture Index, or WPI, to follow changes within the diversity of the wildlife in Bukit Barisan Selatan National Park in southwest Sumatra, Indonesia.

Over an eight-year period, the cameras took pictures of almost all animals, including Sumatran tigers, rhinoceros and Asian elephants, which are becoming more and more rare.

The park has a surface of 1,377 square-mile (2216.066 sq km) and it is one of the last remaining places with protected lowland forests in Sumatra.

The area is also threatened by illegal logging, poaching and agriculture and the results of this survey showed that wildlife loss is surpassing the rate of deforestation.

Today, large animals like rhinoceros, Sumatran tigers and elephants are declining faster than smaller primates or deer, which are only killed for food or if they trespass on crops.

Researchers have an impressive collection of photographs taken from remote locations and after analyzing 5,450 images of tigers, elephants and other animals in the Indonesian park, they concluded that the biodiversity is continuously declining, and in the past eight years, 36 percent of the animals disappeared.

John Robinson, Wildlife Conservation Society executive vice president for conservation and science, said that “the Wildlife Picture Index will allow conservationists to accurately measure biodiversity in areas that previously have been either too expensive, or logistically prohibitive.”

“We believe that this new methodology will be able to fill critical gaps in knowledge of wildlife diversity while providing much-needed baseline data to assess success or failure in places where we work,” he added.

The WPI has virtual photo albums with thousands of images of dozens of animal species all around the park, according to OurAmazingPlanet.

The images are statistically analyzed and the algorithm establishes the diversity and the distribution of a wide range of wildlife.

Tim O'Brien, leader of a study that estimated the efficiency of the WPI, said that “the Wildlife Picture Index is an effective tool in monitoring trends in wildlife diversity that previously could only be roughly estimated.

“This new methodology will help conservationists determine where to focus their efforts to help stem the tide of biodiversity loss over broad landscapes.”

The study is published in the August edition of the journal Animal Conservation.