In 1904, a British duke sent six Himalayan tahr to New Zealand so people could hunt them. A long-term study published in the journal Biological Invasions in 2017 tracked what those animals did to the mountains. Sometimes a gift comes with a very long tail. Its authors, Jennyffer Cruz and colleagues, examined plots that were monitored for more than two decades. Here is what they found.
They were released near Mount Cook, in the Southern Alps, where they found themselves a nice home. Historical sources state that only five of the six animals made it through the trip. There was no linear growth in the numbers.
The Duke of Bedford gave six tahr to the New Zealand government in 1904. At the time of the study, tahr occupied about 9,600 square kilometers of the Southern Alps. Some areas once held up to 30 tahr per square kilometer, according to the study. It also reports that commercial helicopter hunting from 1970 cut the population from about 50,000 to about 2,000 by 1983, within an estimated 6,000 square kilometers of the Southern Alps. DOC estimated about 29,800 tahr in the seven management units on public conservation land in 2023, with a wide range of about 22,100 to 40,150.
Because tahr live in steep, remote terrain, counting is difficult.
The Department of Conservation (DOC) says tahr are goat-like animals from the central Himalayan ranges of India and Nepal. They were brought in as a hunting resource, according to the study.
Numbers have increased since then.
The team used animal droppings to measure tahr activity. Tussock height declined as tahr activity increased. Total plant cover also declined as tahr activity increased, with the sharpest decline at low activity levels. Even so, the authors concluded that tahr had a significant effect on plant cover and tussock height. Hunters are also important in helping to manage tahr numbers. The study’s authors leave us a lesson for the future. They say such long-term impacts should be considered before introducing grazing animals to new areas. More than a century later, tahr still influence how New Zealand manages its mountains.
The study examined 111 permanent plots across eight catchments. The plots were set up in the 1990s and re-measured through 2013. The Himalayan Tahr Control Plan 1993, which guides DOC’s work, allows a managed population of up to 10,000 tahr across Crown pastoral leases, private land, and public conservation land.
Because the land was still recovering from heavier grazing before the 1970s, even so, overall plant cover increased over the course of the study, perhaps.
DOC says tahr have no natural predators in New Zealand, so unless hunters or DOC get involved, their numbers can increase.
