Wallabies hopping out of their South Canterbury containment zone towards national park

Wallaby invaders are knocking on the door of the Aoraki/Mt Cook National Park.

“There are none in the national park, but they are not too far away though,” Environment Canterbury’s wallaby programme leader Brent Glentworth says.

“We have had reports of them being spotted, but none have been confirmed.”

In the South Island, efforts mainly focus on keeping wallabies restricted to a containment zone that is effectively all of South Canterbury, but escapees have been on the increase in recent years, with 454 killed out of the containment zone in 2021.

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Glentworth said 2022 was the first time they'd noticed declines in numbers, sightings and destroyed wallabies outside the containment zone.

In 2021, 629 wallabies were reported and 454 killed, but in 2022 that dropped to 372 spotted and 275 destroyed. So far in 2023, to May 10, Glentworth said there had been 138 reports and 84 killed.

“It takes a huge amount of work to push back to the containment zone. We are almost halfway through this year, and we are on track to be less than last year.”

The identified threat to the park means contractors are constantly tracking and shooting them and from May 16 to 19 were operating in the Twizel River area.

Other Mackenzie Basin wallaby control work on other river systems is planned through to June involving the Godley, Cass, Forks, Pūkaki, Ohau, Macauley and Takapō rivers.

The work is part of ongoing controls under the Tipu Mātoro National Wallaby Eradication Programme.

Glentworth said the programme was confirmed in Budget 2020 and covered Dama wallabies in the North Island and Bennetts wallabies in the South Island.

Wallabies are capable of causing significant adverse environmental effects.

ECan says these effects include “preventing the regeneration of native bush, depletion of forest understory and possible impacts on water quality”.

“Wallabies, deer, possums and hares all impact the biodiversity the same way,” Glentworth said.

“As well as eating pasture they soil the pasture with their faeces which stock then won't touch.”

Wallabies will also damage fences over time as once they find a way through they will keep using the same path and eventually damage the integrity of the fence.

Glentworth said once wallabies knew where a food source was, they would use the same part of the fence and the same track.

New Zealand had Wallaby Control Boards until 1989 when landowners took over responsibility for their control from 1992.

“It has probably gradually got worse from that time, and they've spread outside the area.”

Glentworth said the South Island containment zone was five times bigger than Stewart Island.

“They were never outside of that area until 1998 when we had the first out of zone reports. It was only the odd one until 2010 when numbers started to increase.

“Like any invasive pest they start low and then the numbers pick up.”

The National Wallaby Eradication Programme is a partnership between central and local government plus the Department of Conservation, iwi, farmers, Land Information NZ and other communities.

Glentworth said there were about 11 ground control companies with teams of two to 12 people, plus dogs and thermal scopes working in Canterbury as they looked to control breeding populations outside the containment area, search wider areas where populations may exist and also conduct intensive control within the containment area to reduce continued spread.

He said 2023 represented the end of the third year of the programme and there were three main areas outside the containment zone, around Lake Pukaki, from Pukaki towards Ōhau, and a Waitaki unit on the south side of the Waitaki.

A key focus area was wallabies using rivers as access routes, he said.

A wallaby exclusion fence is also under construction stretching over 55km in the Tekapo River system towards Twizel, replacing a 60-year-old rabbit exclusion fence that has reached the end of its life.

“Wallabies are getting through, and they funnel up the river beds which are a major pathway for them, and we want to reduce that.

“The netting fence is 1.3 metres high, which is about 200mm higher than a normal fence.

“Wallabies will look along a fence for a place to get through or get under. Generally they won't jump.”

The replacement of the rabbit fence is a staged construction as they seek to replace the sections where it is compromised.

When it came to spotting wallabies outside the containment zone, Glentworth said they relied a great deal on the public and reporting them on the website reportwallabies.nz

Wallabies had been spotted as far away as Marlborough and Dunedin, but Glentworth was adamant they didn't get there by themselves.

“We've also destroyed a wallaby near Amberley, but we think that is also a release.”

Otherwise, wallabies have been spotted in northern areas of Otago and through towards the Ashburton lakes north of the containment zone.

Glentworth said with wallabies not going over 2000m above sea level, he believed the Southern Alps were a natural barrier to a full westerly spread.

Controlling wallabies needed a co-ordinated approach Glentworth said, and involved Bay of Plenty, Waikato, Canterbury and Otago regional councils.

“We really need to make the most of the money we have. If everyone is not pulling their weight then we will not get the results.”

Funding of $2.5m had been sought, but not approved, for next year and was needed to continue the gains made.