ACT Parks' report of a recent Brumby sighting at the NSW border follows the release of aerial data revealing feral horse numbers had spiked by 30 per cent in Kosciuszko in two years. More than 18,800 feral horses were sighted in three surveyed areas in NSW last November, up from 14,380 in 2020, the highest density in the region closest to the ACT.

It follows a pause in aerial shooting for several months last year during an evaluation of the Wild Horse Management Plan and a pause in ground shooting during a review of safety measures.

ACT Land Management Minister Mick Gentleman said it seemed NSW was still listening to a small minority with vested interests in keeping horses in the park.

"In the past few years, the very survival of Namadgi has been threatened by fire and by climate change. We have also seen the terrible effect of invasive species, especially hard-hooved mammals," he said.

"It is imperative that both ACT and NSW governments have aligned approaches on feral animal management."

ACT Parks will conduct aerial shooting in Namadgi, Googong and Molonglo reserves in May, with aerial monitoring conducted prior expected to determine whether feral horses had made their way here.

While two Brumbies were shot in Namadgi in 2021, that was the last recorded incursion since populations existed on the western side of the park over a decade ago.

Mr Gentleman said if feral horses did establish themselves in Namagdi, the threat to the Cotter River water catchment and endangered bogs and fens would be significant.

"While we have a strong working relationship with the NSW National Parks and Wildlife Service and a collaborative approach to management issues across the Australian Alps National Parks, we strongly support the resumption of the control program in NSW," he said.

"The presence of horses on the ACT-NSW border is a real threat. Feral animals do not belong in our national parks."

Louisa Roberts, Namadgi National Park acting area manager, said the ACT's zero-tolerance policy meant feral-horse management was well ahead of other jurisdictions.

"We've managed to be on top of these issues before they get to the level that they are elsewhere," she said.

"And it's gotten to a really difficult stage."

Aerial shooting in Namadgi will also target pigs, goats and deer, with three years of La Nina conditions expected to mean higher numbers of feral pests.

Ms Roberts said damage to Alpine bog systems, one of the most fragile and threatened ecosystems, was already present in NSW and Victoria.

She said the three jurisdictions were fairly well connected on the issue of Brumby management, while coming at the issue from angles.

"We're very lucky here in the ACT, that we're kind of right at the front of the wave," Ms Roberts said.

"We know those horses are lurking over on that NSW side, but we're prepared."

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