Cassowaries (genus Casuarius) are very large flightless birds native to the tropical forests of New Guinea and northeastern Australia. Some nearby islands also have small cassowary populations, but it is not known if these are natural or the result of the New Guinea trade in young birds. They are frugivorous; fallen fruit and fruit on low branches is the mainstay of their diet. They also eat fungi, snails, insects, frogs, snakes and other small animals. Recently, they have also been observed to attack humans, though this usually only occurs in self-defense when humans intrude upon the birds' territory or cause them to feel threatened.