“It is a groundbreaking study, because it is the first to demonstrate, experimentally, a direct connection between the effects of culling and specific psychosocial harms,” says Lori Marino, a neuroscientist and expert on dolphin behavior at Emory University in Atlanta, who was not involved with the research. “It shows unequivocally that elephants are psychologically damaged by culling.”

Wildlife officials often used culling as a conservation tool in South Africa from the 1960s to the 1990s. (It is still reserved as a management tool there.) At the time, wildlife managers worried that if there were too many elephants in a fenced reserve, like the famed Kruger National Park, the behemoths would ultimately destroy the habitat, eating or trampling all the vegetation and uprooting the trees. During a cull, a helicopter pilot herds an elephant family into a tight bunch. Professional hunters on the ground then shoot the animals as quickly as possible. Only young elephants ranging from about 4 to 10 years old are saved. Park officials typically shipped them to other parks that lacked elephants or had smaller populations to increase the herds, because elephants are popular with tourists.

“Some of these elephants ended up in Pilanesberg National Park,” in South Africa’s North West Province where part of the new study was carried out, says Graeme Shannon, a behavioral ecologist at Colorado State University, Fort Collins, and the lead author of the new study. “Twenty to 30 years have passed since the actual cull and relocation.”