As the park is a national nature reserve and a Site of Special Scientific Interest, all dog owners are required to keep their dogs under control while in the park. This includes not allowing their dog to disturb other park users or disrupt wildlife. In 2009, after some incidents leading to the death of wildfowl, the park's dogs-on-leads policy was extended. Park users are said to believe that the deer are feeling increasingly threatened by the growing number of dogs using the park and Royal Parks advises against walking dogs in the park during the deer's birthing season.