Between them, two of the country's worst pest species strip plants, rip up pasture and prey on young birds.
The new book Rabbits and Possums in New Zealand details how these destructive species were introduced, supported and went on to thrive until they were identified as pests.
Lloyd Esler, a natural history enthusiast from Invercargill, has dug deep in the archives to tell of the story of the role rabbits and possums once played in New Zealand's early economy and how that all changed.
Esler says rabbits were brought here for a rather odd mix of reasons.
“There were four reasons why we got rabbits - one was for food; one was for sport; one was for sentimentality and one for God‘s work uncompleted.”
Some early British settlers were of the belief that all of God’s creatures should be spread through the world.
To create a more familiar environment in British colonies and dominions, ‘acclimatisation societies’ introduced rabbits and various other species from the mother country.
In the 1860s the first batch of rabbits arrived – and about half a dozen were liberated.
“They were released on Sandy Point in Invercargill and the problem started from there,” says Esler.
The word ‘ecology’ didn’t appear until 1886, Esler says, but a chat with gamekeepers back in Britain would have given the acclimatisers a clue as to what could happen.
“Within 15 years there was an estimated 100 million rabbits in Otago.”
The earliest reference to rabbits as 'pests' Ensler could find was in a 1868 newspaper article.
“This is five years after they were liberated. They’re eating crops, stock were stumbling in rabbit holes and whole fields of wheat were being destroyed overnight… The rabbits jut expanded out across Invercargill and they spread across the Southland plains.”
Once the rabbits reached the dry Otago hill country they were in “optimum rabbit territory” - there were no predators and the population exploded.
It became so bad land was abandoned, says Esler.
“Within a few years, much of Central Otago was abandoned. Seven rabbits eat as much grass as one sheep and there were 70 times as many rabbits as sheep.”
Until poisoning and predators came along the rabbits had the upper hand.
But they weren’t just a pest, they were also a huge industry.
The exportation of rabbit skins to the fur hat market of the UK started in the 1870s. At its peak, in 1924, one million rabbit skins were sent to Britain.
Then when freezing and canning technology arrived, rabbit meat became a commercial product.
Because rabbiters almost ‘farmed’ rabbits - keeping a population going that would give them work year on year - the population never really declined, so in 1950 the government de-commercialised the rabbit.
With no incentive to keep rabbit population alive, by the 1980s they were almost extinct in some areas.
That was until the Labour government removed grants paid to farmers for rabbiting and the population started to climb again.
Esler says the possum was brought to New Zealand for one reason alone – fur.
In 1858, the first black possum was introduced from Tasmania to supply the fur trade.
They were then shifted all around the country by colonisation societies and protected quite stringently to allow the population to build up, says Elser.
“So that people could trap them to make possum skin rugs.”
No heed was given to the devastating effect they would have on forest ecology, he says.