Estimates point to the genetic separation of the populations north (Nilgiris) and south (Anamalais) of the Palghat Gap about 1.5 million years ago.

The Nilgiri tahrs formerly ranged over these grasslands in large herds, but hunting and poaching in the 19th century reduced their population.

[1] The Nilgiri tahr is primarily threatened by habitat loss and disturbance caused by invasive species, and in some sites by livestock grazing, poaching and fragmentation of the landscape.

[7] Their range extends over 400 km (250 mi) from north to south, and Eravikulam National Park is home to the largest population.

A small population of tahrs numbering around 200 is known to inhabit the Boothapandi, Azhakiyapandipuram, Velimalai, Kulasekaram, and Kaliyal Ranges in the Kanyakumari district of Tamil Nadu [9] and another small herd of less than 30 animals is known to inhabit Ponmudi Hills in Trivandrum district of Kerala.