If unchecked, wallabies could spread across a third of the North Island within 50 years. Photo / Andrew Warner
A joint effort is being used to control pest wallabies – and ultimately eradicate them - from the central North Island.
Native to Australia, wallabies were introduced to Kawau Island in the Hauraki Gulf by former New Zealand Governor Sir George Grey around 1870.
They were subsequently released near the Rotorua Lakes area in 1912.
Central North Island wallaby programme leader Davor Bejakovich said the pests were now present across 200,000 hectares in the central North Island.
He said it was estimated if no control work was undertaken, wallabies’ spread could affect a third of the island within 50 years.
The Bay of Plenty and Waikato regional councils are part of the Tipu Mātoro National Wallaby Eradication Programme.
Bejakovich said this was a collaborative effort between Biosecurity New Zealand, iwi, the Department of Conservation, Forest & Bird, Federated Farmers, Land Information New Zealand, farmers, researchers, landowners and communities.
“The programme’s success relies on first preventing their spread from areas where they are already established, which is known as the containment area, and progressively working inwards with control over time.”
In the central North Island, the containment area falls mostly in the Bay of Plenty but crosses the border into the Waikato around Rotorua.
Bejakovich said wallabies had a huge appetite for many of our native flora, which prevented forest regeneration in the long term, changed the forest structure, and reduced their ability to support native birds and other wildlife.
“Wallabies also love pasture grasses, which means they compete with livestock for food.”
Bejakovich said the impact on plantation forests could also be significant.
“Timberlands, who manage the Kāingaroa forest, estimate that the one metre of growth normally expected in the first year from plantings can be reduced by half when browsed by wallabies.
“If we don’t stop the spread of wallabies, they will have even more significant impacts onour native ecosystems and through lost farm and forestry production.”
Because wallabies are nocturnal and cautious, Bejakovich said, they could be hard to find and control.
“Current programme activity is focused on surveillance and control of ‘satellite’ populations in areas outside of the containment area, in buffer areas within containment at critical locations of potential spread, and to reduce reinvasion where we have undertaken successful control,” he said.
“Given wallabies are active primarily between dusk to dawn, the use of thermal optics mounted on firearms and thermal and IR cameras mounted to drones has been a game-changer during night-shooting operations.”
Bejakovich said contractors with specially trained wallaby indicator dogs and trail cameras were used to locate and determine the extent of wallaby populations.
“It can be like finding a needle in a haystack when you are potentially looking for only one or just a few in sometimes difficult terrain.”
Where wallaby populations are confirmed outside of the containment area, councils work with the landowners to plan and deliver wallaby control (currently at no cost to landowners).
In the longer term, Bejakovich said, the focus was on strategically targeting wallaby populations inside the containment area.
“With the help of landowners, iwi, and community groups, the aim is to progressively reduce the size of the containment area while simultaneously researching and developing new tools for eradicating wallabies.”
Bejakovich said coordination was key.
“Sporadically targeting large numbers of wallabies via night shooting can cause them to become ‘gun-shy’ and can scatter them into new or previously cleared areas.
“Habitat and land management changes, like forest harvesting, may also cause wallaby to move into new areas.”
Biodiversity-focused projects within the containment area may include wallaby control as part of their wider pest management objectives.
Landowners/managers located within the containment areas can contact their council biosecurity staff for advice on wallaby control options to suit their situation.
Last year, a 12.5km wallaby-proof fence was completed, running from Rotorua along State Highway 5, following the boundary of Whakawerawera Forest to Lake Rotokākahi.
As part of the progressive containment strategy, Bejakovich said the fence helped to stop wallabies from crossing the highway and spreading south, where wallaby control was successfully reducing their numbers.
Retrofitting wallaby-proof netting to existing fences has also been undertaken at other potential spread points.
Wallabies are classified as an “unwanted organism” under New Zealand’s Biosecurity Act 1993 – making it illegal to hold, breed, display, move or transport them without specific authorisations.
There are also rules in the Bay of Plenty and Waikato’s regional pest management plans that make it illegal to keep live wallabies.
Bejakovich said it was important to remember that wallabies were pests, not pets.
Sightings can be reported online at reportwallabies.nz.
Bejakovich said that, depending on the location in relation to the containment area, the sighting may result in the use of detector dogs or trail cameras.