The High Court in Wellington has heard an application from the Tahr Foundation to stop the Department of Conservation's planned cull of the Himalayan goats in national parks.
Dr McSweeney told this month's West Coast Tai Poutini Conservation Board meeting that the tahr population was exploding in the high country, and recreational and trophy hunters were not able to control it.
"But based on the return figures from the aerial-assisted trophy Hunters (AATH), they have only shot an average of 67 bull tahr per year in the two national parks over the last five years.
"That is estimated to be as little as about 5 percent of the bull tahr population in the parks so bull tahr numbers in the parks have skyrocketed."
Covid-19 restrictions had made things worse, with no hunting for two months during the roar and the international tourism-hunting sector at a standstill.
Conservation Authority chair Edward Ellison, an Otago sheep farmer, had reported recently that herds of tahr numbering in the hundreds of animals were being seen in the river catchments both north and south of the national parks in the Rangitata, Landsborough, Wanganui and Whataroa Valleys, Dr McSweeney said.
"Some pastoral leases are now effectively tahr farms but they are administered by LINZ not DOC so there are jurisdiction issues in controlling tahr numbers on these leases.
"One of DOC's West Coast senior staff in May reported seeing hundreds of tahr in the Lambert River valley, a tributary of the Wanganui River. He shot 30 before he ran out of ammunition.
"A NZ Conservation Authority member in early June also reported seeing hundreds of tahr while on a hunting trip in the Havelock catchment of the Rangitata River immediately across the Southern Alps opposite the Wanganui River. He shot four bulls as did his companions on this trip."
National parks, where tahr are an illegal introduced species make up only about 20% of the tahr's range and there were many other places outside the Parks for hunters to shoot tahr, he said.
The deer population was also exploding, and Dr McSweeney said he was now seeing the results in forest near his tourist lodge at Lake Moeraki.
"I had a visit from Lou Sanson in early June [DOC's director-general]. I took him for a walk down the river to show him the difference between two areas - one where deer had been browsing and one where there'd been none for many years because they would not cross Highway 6 to enter this forest.
"But we found the deer had got into the second area - completely chewed that out as well."
DOC staff at the board meeting told the Greymouth Star there were no immediate plans or funding to step up deer culling in the region but it would continue to target priority conservation land.
West Coast operations director Mark Davies would be taking part in today's injunction hearing, he said.
DOC says tahr browse on native plants including snow tussock, alpine buttercup and mountain daisies and in extreme situations can turn tall tussock and sub alpine shrublands to grassy turf or bare ground.
A statement provided said high tahr numbers had led to a drastic change in the vegetation at Zora Canyon, South Westland, with tall snow tussocks in some places almost gone.
Ngāi Tahu representative Kara Edwards told the board the iwi was working on the tahr issue with DOC in a co-governance role but had not formed a collective view on non-indigenous kai species.
"For some of our Ngāi Tahu people, tahr and deer are part of their sustenance, but others are very conservation-minded.
"It's fair to say that tahr are not a taonga species and there would be a lot of indigenous species we would put ahead of them.
"DOC is working very hard on this and I have to say the threats to them that have been bandied about are absolutely inappropriate."
The board agreed to hold off on making a submission to DOC on the tahr issue while it was before the courts.
- By Lois Williams, Local Democracy reporter
