agencies to support wildlife management programs, the purchase of lands open to hunters, and hunter education and safety classes. Since 1934, the sale of Federal Duck Stamps, a required purchase for migratory waterfowl hunters over sixteen years old, has raised over $700 million to help purchase more than of habitat for the National Wildlife Refuge System lands that support waterfowl and many other wildlife species and are often open to hunting. States also collect money from hunting licenses to assist with management of game animals, as designated by law. A key task of federal and state park rangers and game wardens is to enforce laws and regulations related to hunting, including species protection, hunting seasons, and hunting bans. Varmint hunting Varmint hunting is an American phrase for the selective killing of non-game animals seen as pests. While not always an efficient form of pest control, varmint hunting achieves selective control of pests while providing recreation and is much less regulated. Varmint species are often responsible for detrimental effects on crops, livestock, landscaping, infrastructure, and pets. Some animals, such as wild rabbits or squirrels, may be utilised for fur or meat, but often no use is made of the carcass. Which species are varmints depends on the circumstance and area. Common varmints may include various rodents, coyotes, crows, foxes, feral cats, and feral hogs. Some animals once considered varmints are now protected, such as wolves. In the US state of Louisiana, a non-native rodent, the coypu, has become so destructive to the local ecosystem that the state has initiated a bounty program to help control the population. Beavers from North America constitute an invasive species in Tierra del Fuego, where eradication attempts are ongoing. Fair chase The principles of the fair chase have been a part of the American hunting tradition for over one hundred years. The role of the hunter-conservationist, popularised by Theodore Roosevelt, and perpetuated by Roosevelt's formation of the Boone and Crockett Club, has been central to the development of the modern fair chase tradition. Beyond Fair Chase: The Ethic and Tradition of Hunting, a book by Jim Posewitz, describes fair chase: "Fundamental to ethical hunting is the idea of fair chase. This concept addresses the balance between the hunter and the hunted. It is a balance that allows hunters to occasionally succeed while animals generally avoid being taken." When Internet hunting was introduced in 2005, allowing people