Sport hunters are depleting lion and cougar populations as managers respond to demands to control predators that threaten livestock and humans, according to a study published in the June 17 issue of PLoS One. The study was led by Craig Packer, a University of Minnesota professor and authority on lion behavior, who worked with an international team of conservationists.

The study looked at numbers of lions and cougars killed by hunters over the past 15 to 25 years in Africa and the western United States. The analysis suggested that management agencies often adjusted quotas to control rather than conserve the big cats in areas where humans or livestock were threatened.

Sport hunting takes a significant toll on these large feline species because replacement males routinely kill their predecessors' cubs to improve their mating opportunities. (Killing cubs forces female lions into estrus or "heat.") The team of scientists confirmed this effect by comparing the impact of hunting on populations of lions, cougars and leopards with its impact on black bear populations because male black bears do not routinely kill infants of other males.

Lion and cougar populations have suffered the greatest decline in African countries and U.S. states where sport hunting has been most intense over the past 25 years, the researchers found. Leopards were not as affected as lions and cougars, most likely because they benefited from reduced numbers of lions. Black bears, by contrast, appear to be thriving despite the thousands of bears killed by hunters.

The study results point to the need for new approaches to protect humans and livestock and to manage sport hunting without endangering these vulnerable species. One possibility would be to restrict sport hunting to older males whose offspring have matured.

"We need to develop scientifically-based strategies that benefit hunters, livestock owners and conservationists," Packer says. "It's important to educate the public about the risks these large predators pose to rural communities and to help hunters and wildlife managers develop methods to sustain healthy populations."

"Packer's colleagues included co-authors Luke Hunter, Executive Director of Panthera and Kristin Nowell from the International Union for the Conservation of Nature Species Survival Commission (IUCN/SSC) Cat Specialist Group, as well as Dave Garshelis, Chair of the IUCN/SSC Bear Specialist Group."