Tahr cull tops 12,000
But native plant life may take years to recover
The Department of Conservation and hunters have culled more than 12,000 tahr in its ‘‘feral range’’ in the Southern Alps since July, but there is still much work to do.
DOC, which has a cull target for 10,000 tahr within the range, estimated the Himalayan mountain goat’s population was as high as 35,000 at its peak on conservation land.
The tahr ‘‘feral range’’ encompasses more than 1.7 million hectares between the Haast Pass and the Rakaia catchment, which includes Aoraki/Mt Cook and Westland/Tai Poutini National Parks.
In the Aoraki/Mt Cook and Westland/Tai Poutini parks more than 5500 tahr have been culled since last July in a control programme costing DOC about $1 million a year.
Tahr Project leader James Holborow said it was difficult to know exactly how many tahr there were, as they could only monitor the population on conservation land.
‘‘To give an idea of the density, one contractor managed to cull more than 1000 tahr in the Ben Ohau Range over two days in July 2019.
‘‘The eastern side of the Southern Alps is the highest density of tahr you would find. It’s like a superhighway for tahr.’’
Holborow said that since winter 2019 more than 12,000 tahr had been culled with the help of hunters, wild animal recovery operators (waros) and contractors.
‘‘It’s been a really good result. One of the big things we have learnt last year is that during winter especially, you only have a short window weather-wise to have all your procedures in place.
‘‘It’s a really good time for tahr hunting, we’re keen to see hunters out there and doing their bit.’’
Holborow said there would be a ‘‘serious effort’’ in the key national parks over winter.
‘‘For the last while we have been targeting juveniles and females, and leaving the bull tahr for the hunters.
‘‘We’ve also been doing some intensive surveys of the tahr population, we’re currently working with Land Information New Zealand (Linz) on that.’’
Holborow described tahr as ‘‘adaptable and sociable’’ animals.
‘‘It’s fascinating discovering where tahr roam.’’
DOC ecologist Brian Rance said tahr caused all sorts of problems for native tussocks and plants, especially in the Ben Ohau Range.
‘‘But it’s something you notice over time. It’s largely dependent on the number of the animals. At one stage, you might have seen tall tussocks around the Ben Ohau Range as high as one metre, now some of them are only up to your ankles,’’ Rance said.
Although there had been a significant effort to control the population in the past year, Rance said it could take a ‘‘very long time’’ for the native plants to fully regenerate, or even get back to their original state at all.
‘‘In the next year, we will probably see only subtle changes. Some of the tussock species might start to grow back.’’
DOC biodiversity ranger Ingrid Gruner said there had been an extensive monitoring programme of eight tahr ranges since 1993, carried out in tandem with Landcare NZ.
‘‘The key indicator of the tahr’s effect is on the height of tussock. Over time, the height of tussocks has decreased,’’ Gruner said.
‘‘Tahr are the biggest browser of native plants in this area. They’re particularly problematic because they ‘mob up’ in groups.
‘‘Some of the plants they like, such as the Mt Cook buttercup, are among the most threatened in the country.’’
Holborow said that over the next year, DOC would be working closely with Nga¯i Tahu, Linz, hunters and waro operators to develop a long-term control plan that is fit for purpose.
‘‘Success for us would be continuing to work together with all the relevant groups so that we can get that number down to 10,000,’’ he said.