At least 1141 of the 5487 known mammal species are threatened worldwide, with 188 listed in the highest risk âcritically endangeredâ category. The âRed Listâ assessment, issued by the International Union for the Conservation of Nature, said one in three marine mammals were also threatened and the world Wildlife Fund said this was a warning for the survival of New Zealandâs marine mammals. WWF New Zealandâs marine programme manager Rebecca Bird said nearly all of New Zealandâs native mammals were found at sea. The many threatened with extinction include: the blue whale, fin whale, sperm whale and New Zealand sea lion. The list also includes the Hectorâs dolphin, though the critically endangered mauiâs dolphin â internationally recognised as the worldâ rarest marine dolphin â is not listed separately because it is recorded as a North Island subspecies.