A man with deep knowledge of gangs says an explosion in the Otago-Southland region's gang population comes down to competition in the North Island over matters including a $600 million methamphetamine market.
Police estimate the gang population in Otago-Southland is increasing at 30 per cent a year.
Seven Sharp reported the most visible sign of a gang presence in Southland is the Mongrel Mob's southern headquarters in Mataura.
For his safety, the programme couldn't name the man who knows the gangs intimately, report how or where it met him or conduct its interview with him in one spot.
Travelling with a reporter in a car, the man explained competition among gangs in the North Island.
"People become quite aggressive," he said. "When you look at things from a territorial perspective, you can't have too many people eating out of the same plate. You got to go to where the water is, replenish that resource so to speak."
Big international gangs like the Comancheros and Bandidos, Asian syndicates, and even the Mexican cartels are now in New Zealand.
"Some of the most sophisticated drug smuggling drug cartel operations are happening out of maximum security prison cells," the man said.
New Zealand's home-grown gangs have been feeling the heat.
Another man who knows the gangs well is Detective Superintendent Greg Williams of the New Zealand Police Organised Crime Group.
"We've seen really a number of things coming together - decrease in the price of meth, try and expand into other markets, having to compete with other gangs. The Australian gangs are now well established here also," Mr Williams said.
The anonymous man explained the gang's approach, saying: "You need to think, okay how do we mitigate this risk? We need to get out in amongst a community that's more naive I suppose."
Detective Superintendent Williams said: "What you've got is a decision amongst the gangs, in particular the Barbarians, to expand into what they see as vulnerable markets, or potential markets, in the South Island, we would say for the sale of drugs."
No one is talking about the fact that methamphetamine is rife in Queenstown- man who knows gangs intimately
In Te Anau last week, 16 new gang members were reportedly patched.
The anonymous man said people look at Te Anau as a tourist attraction where people go to have fun.
"But methamphetamine is being distributed out of there. Why? Because that drug is clever, it needs to stay off the radar."
He added: "No one is talking about the fact that methamphetamine is rife in Queenstown."
And those who a few years ago wouldn't have touched meth are now using it. They include farm workers, among others.
Mr Williams said the gangs will hand out meth for free as they move to build up a market.
"The gangs are quite cunning, so they'll hand it out for free. It's a very addictive drug . A lot of people sadly are introduced it through familial links, through families as well. So you can rapidly build up a market within a community," he said.
A problem once confined to poorer urban areas has now spread all the way to pristine Fiordland, the furthest reaches of New Zealand.
The police estimate New Zealand's methamphetamine problem costs $1 billion a year in social harm.