structural:summarization
New Zealand

First arriving before 1800 (perhaps on James Cook's vessels), brown rats pose a serious threat to many of New Zealand's native wildlife. Rat eradication programmes within New Zealand have led to rat-free zones on offshore islands and even on fenced "ecological islands" on the mainland. Before an eradication effort was launched in 2001, the sub-Antarctic Campbell Island had the highest population density of brown rats in the world.