Researchers surveying for endangered primates in national parks and forest reserves of Ivory Coast found, to their surprise, that most of these protected areas had been turned into illegal cocoa farms, a new study reports. The researchers surveyed 23 protected areas in the West African nation between 2010 and 2013 and found that about three-quarters of the land in them had been transformed into cocoa production.

The Ivory Coast is the largest producer of cocoa beans, providing more than one-third of the world's supply. Cocoa is the main ingredient in chocolate.

"The world's demand for chocolate has been very hard on the endangered primates of Ivory Coast," said W. Scott McGraw, co-author of the study and professor of anthropology at The Ohio State University.

McGraw said the original goal of this research was "just to do a census of the monkeys in these protected areas."

"But when we started walking through these areas we were just stunned by the scale of illegal cocoa production. It is now the major cause of deforestation in these parks," he said.

"There are parks in Ivory Coast with no forests and no primates, but a sea of cocoa plants."

The study appears in the March 2015 issue of the journal Tropical Conservation Science.