Hunting is the practice of killing or trapping any living organism, or pursuing it with the intent of doing so. Hunting wildlife or feral animals is most commonly done by humans for food, recreation, or trade. In present-day use, lawful hunting is distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law. The species that are hunted are referred to as game and are usually mammals and birds. Hunting can also be a means of pest control. Hunting advocates state that hunting can be a necessary component of modern wildlife management, for example, to help maintain a population of healthy animals within an environment's ecological carrying capacity when natural checks such as predators are absent. In the United States, wildlife managers are frequently part of hunting regulatory and licensing bodies, where they help to set rules on the number, manner and conditions in which game may be hunted.