Feral animals are present within the National Park, the ones presenting the most serious problems being brumbies and pigs. In 2007, culling of both species began by riflemen in helicopters or airplanes. In 2008 the third phase of an aerial culling of Brumbies took place, by shooting 700 horses from a helicopter, in Carnarvon National Park. Such aerial culling is a contentious issue to some members of the public. However, there is little doubt that both species cause considerable alteration to the values the park is designed to protect. Through their grazing and their repetitious patterns of movement, feral horses alter the composition of the ground cover, and this can accelerate erosion through over-grazing and excessive hoof traffic. Feral pigs are thought to be responsible for the localised extinction of the Australian brush-turkey from some areas of this National Park.