special report
Pest control of introduced mammals such as rodents and possums help control wilding conifer spread, according to a study done last year.
Scion invasion ecologist Tom Carlin led research into the effect seed eaters such as possums and rats had in consuming pine seeds.
The study was carried out in Arthur’s Pass of the Southern Alps.
Scion is a Crown research institute that specialises in research, science and technology development for the forestry, wood product, wood-derived materials.
The findings that possums were eating the seeds came as a surprise to scientists as the seeds are small about 2mm-4 mm on average so it was supposed possums would have difficulty in finding them.
Not so surprising relative to the small size of seeds and animal body weight was that rats and mice were the biggest eaters. However possums ate a greater quantity of seeds per animal.
In dense forests, home to large populations of mammals, about 90 percent of seeds was eaten whereas in tussock habitat, only half of the seed quantity was consumed.
That highlighted how vulnerable those areas were to invasion by pines, Tom Carlin said.
Another surprise was that birds, whether native or introduced, had no interest in making a meal of the seeds especially since some “experts” considered birds would be taking seeds.
The results of the research strongly point to programmes of introduced mammal control or attempted extermination, would probably result in “increasing invasive conifer populations by reducing seed predation pressure”.
However, finding that mammals were an asset in the fight against wilding pine spread fight gave hope, as since it was almost certain the country would not be able to exterminate possums and rats, that wilding pine spread would be lessened.
The seeds do not survive through the gut of possum or rats scientists added.
There is so much ‘misinformation” on-line about possums. Firstly they are accused of being the main spreader of bovine Tb.
Nonsense! Invariably Tb is spread on the back of stock trucks because the skin test used to detect Tb in stock has an error rate of 30% so there’s a very good chance infected animals are passed as clear.
They are accused of damage to forest.
Nonsense. NZ’s bush evolved heavily browsed by flightless birds (e.g. moa, takahe) and the canopy by vegetarian birds such as pigeon (kereru), kokako etc and even insects (e.g. beech roller caterpillars) and even snow-grass tussock by grasshoppers. It’s all there in scientific studies.
They are called predators and accused of eating birds eggs.
Nonsense! The possum is a herbivore and native to Australia. Australia has abundant bird life. The photos in NZ used by DoC, were shown by a Nelson conservationist to be “jacked up.”
The possum is just a scapegoat for illogical ideology and for a government department to grab more money in departmental vote allocation for a fictitious pest.
Well said Fred.
Now the Scion research shows the complexity of the food web and that possums – and even rats – in stemming the invasion of wilding pines, serve a purpose.
Thank you CORANZ for posting the revealing research.
Well, well, well, while possums and even rats are contributing to keeping wilding pins at bay, the bureaucrats in the Department of Conservation are doing little.
My observation in Marlborough is that DOC has sat on its hands while Douglas Fir, Contorta pine and radiata pine have been allowed to spread. The evidence can be seen in mature trees even by 4WD tracks on public lands. A mature pine is at least 20 years old, probably more like 25.
So for 25 years DOC has done nothing but let the trees grow and just drive past them.
Ironically the adult trees are now being logged. I wonder where the money goes – to DOC for doing nothing? Bureaucrats operate in very funny, peculiar ways.
Or perhaps words like idle and irresponsible should be used?
How come this intriguing research didn’t seem to get much airing from the media, both newspapers and TV?
Any good honest research never gets into the media if it impedes the DoC agenda. The latest example of media clamming up is the upcoming poisoning of Stewart Island, has anyone seen anything in any media?
I know it’s very low humour but it’s always intrigued me that the word “bureaucrat” ends with “rat”.
I’ve mostly encountered the bureaucrat species through health politics where this pest (along with the political species) has contaminated the wonderful ethical basis of health care as expressed by the inscription on a Waimate statue to the first woman doctor in New Zealand. It reads, “the beloved physician, faithful unto death”.
So too with the bureaucratic/political agenda regarding the environment. I suppose one could take the approach of, “Forgive them for they know not what they do”, but I, for one, have long lost patience with their stupid, self-seeking agendas. Oh for a government which would learn from history and treat the environment according to well-established research and facts.
Well Well, indeed what next will DOC come out with? The only way to control possums is by man on foot but if a reason not to do anything can be found that will allow the rats and possums to stay because they are eating all the seeds, DOC will grab it. This way they can stay by the fire and pat each other on their backs. As for the trees, they will be a resource one day as I’m sure something will be found for their use, and the back-patting will continue .
Here we are 2025 STILL using Failed 1950s methods for controlling Possums. /// New Zealand should really have capitalised on our FREE TRADE Agreement with PRC China by now ? What better than having someone that will EAT our introduced animals, plus use their Fur ! How so > China has the Red Tree Panda ( not much larger than the Possum ), that is slowly being eaten out in the Wild, also they make use of the Fur ? with some of their many cultures using it in a Wedding dress. ///// N.Z. Possum exports could fill the gap & take the pressure off their Red Tree Panda becoming extinct ? & we even have “RED” Possums ! ///// Re Saving the Garden Fruit Crop right now , from being eaten by Mr & Mrs Possum ? Place Solar Lamps around the Fruit Tree’s & Possums as we know are Nocturnal & don’t like the LIGHT ! Not a 100 percent, only it might save the bulk of the Fruit Harvest . //// Happy New Year .
The irrational assumption that introduced species that are not domesticated should or can be eradicated to protect “native birds” has become the basis for a financial industry.
The current and future incomes of productive working people are diverted to the beneficiaries of this industry who produce nothing of value in return for what they do.
The reduction of the numbers of target species is soon reversed by increased breeding to perpetuate the profits of the people in the Predator Free industry at the expense of productive working people who are forced to keep paying.
The estimated cost of this Predator Free Ambition was originally 9 Billion dollars.
That cost is now estimated to be over 18 Billion and will keep increasing because eradication of the “predators” is not possible or even desired by the beneficiaries of the industry.
The productive working people who fund this industry receive nothing in return for their money. Their real incomes continue to decrease in relation to the costs of living.
The main function of the people in our government has become the distribution of productive workers incomes to politically influential people who provide little or nothing in return for it.
Elections will not help the struggling wage and salary workers because none of the influential members and funders of the political parties care about them.
What we call the economy is the daily efforts of ordinary people that produce the goods and services others value and can willingly pay for.
The tax revenue that people in governments take and spend is all generated by those productive working people.
A great deal of that tax revenue is spent on things like the predator Free industry that provide little or no benefit for the people who paid.
There might be a great opportunity for a political party that would tell the abused productive working people the truth and represent them in the government?
The Labour party no longer represents or cares for productive workers.
Charles you are Correct ! As I see it after working a Lifetime , both Self Employed & 15yrs for the Pest Destruction ( Rabbit ) Board , We must ASAP implement a modern method of Predator Control ? >> “Incentive Payment ” ! The pay RISSES when Predator numbers DROP , thus keeping the Trappers KEEN & on the Case , in no way should this be confused with failed Bounty Farm Scams used years ago . //// How would an Incentive Scheme be Funded ? with Lotto / Public Donation Etc. & maybe helped along with the profit from exporting Possum Meat & Pelts ? up to PRC China . /// As a Nation we must do much MORE & save the best Tourist Asset we have ? our Native Fauna > BIRDS ! // Starting with STOATS , they are a “Super Predator” , related to Otters ? can swim & tolerate cold conditions, plus clime ( unlike Ferrets ) . /// Of note the COOK ISLANDS of late , introduced a Reward ! that saved their Native Lorikeet ? U.K . DEFRA ( MAF ) , had the Incentive Payment on the Coypu ? > huge South American water Rat , with great success, back in the 80s.