Ornithologists long thought that there was one species of Takahe, Porphyrio mantelli, but in 1996 the case was made to split the species into two: Porphyrio mantelli and Porphyrio hochstetteri.

The species Porphyrio mantelli is extinct. These Takahes once lived only on North Island, New Zealand. The species is known mainly from skeletal remains. Its decline seems to have been caused primarily by the loss of its alpine grassland habitat to forest, starting from about 12 000 years ago. Hunting by the Maori probably also contributed to the decline.

By 1900, all Takahes were believed to be extinct. However, in 1948, some birds were discovered in an almost inaccessible valley on South Island, New Zealand. These birds are now identified as the other species: Porphyrio hochstetteri. This species is almost extinct. Hunting pressure, introduced predators (especially the stoat) and loss of its scrub and grassland habitat caused by introduced grazing animals (such as deer) are the principal causes of the decline. A recovery programme has been established, and their numbers are increasing very slowly. In 2007, there were an estimated 150 to 200 birds.

As they evolved, both species of Takahe lost their ability to fly. Takahes of the living (extant) species, Porphyrio hochstetteri, are about 63 cm (25 in.) long.