The South Island's wallaby control team is confident it's reducing the spread of the pest.
So, they were shocked when there were reported sightings of them roughly 160km away from the containment zone in south Canterbury.
It's estimated, on average, wallaby populations can spread up to 2km every year - eating their way through farms and native flora.
In the South Island, they now inhabit 1.3 million hectares outside of the 900,000-hectare containment area.
"They swam the Waitaki, also crossed dams on the Waitaki," said Canterbury Wallaby Programme leader Brent Glentworth.
The nocturnal animal has also spread through Tekapo and across into the western Mackenzie Basin.
"We've had them as far as Marlborough, we've had one in Wellington, we've had them in Balclutha," Glentworth added.
And, most recently, the pest may have been spotted in Christchurch on the Port Hills.
There have been five reports of wallaby sightings there. So far, 11 days have been spent searching for the pest - but the sightings are still unconfirmed.
"They don't just get there by themselves, they've had a ride in the boot of a car unfortunately," Glentworth said.
That ride was likely with recreational hunters who shot a wallaby with a joey in her pouch, Environment Canterbury said.
Recreational hunters agree it's unlikely they got there by themselves.
"Whoever it is, they probably don't represent whatever group they're a part of and I wouldn't expect that from the hunting group necessarily when you look at the group of hunters out there," recreational hunter Pete Caldwell said.
"Wallabies have adverse effects on the environment, hunters are aware of that and they do control them for that reason and also the thrill of the chase."
Recreational hunters are a group Environment Canterbury acknowledges help to control pest numbers.
"If you are recreational hunting in south Canterbury and you destroy a doe with joey in pouch, please humanely destroy joey as well," Glentworth pleaded.
Experts said, if left, wallabies could spread to more than a third of New Zealand in the next 50 years.
