Editor’s note:– A reader has unearthed an interesting study that shows a benefit of stoats.
Stoats in South Island alpine areas prefer to eat small mammals and ate surprisingly few birds. Stoats in alpine areas strongly preferred ship rats, according to research in 2020 by DOC scientist Jamie McAulay.
One hundred per cent of stoats from Fiordland National Park and 90 per cent of stoats from Mt Aspiring National Park had mammal remains in stomachs but at Nelson Lakes National Park where there are reportedly no rats, only 50 percent had mammal remains in guts.
In Nelson Lakes, the stoats ate large numbers of native wētā and skinks, McAulay and colleagues found.
They analysed the stomach contents of stoats from the three alpine areas – Fiordland, Aspiring and Nelson Lakes – over three seasons.
“The proportion of birds in stoat diet was lower than expected at most sites and in most periods, and generally lower than reported by [other researchers]. Passerines contributed less than 2 per cent to stoat diet in most samples, among the lowest proportions recorded anywhere in New Zealand,” they reported.
Passerines are birds that perch, broadly speaking.
The stoats from Aspiring and Fiordland had no bird remains in their guts.
DoC is reinventing the wheel. It’s been well known for decades the main prey of stoats is rats. However it does no harm to repeat it. DoC might then learn something about wild food chains.
I guess they eat a lot of eggs which probably don’t show up as easily in the gut.
It is an interesting point “Bush-man” raises.
I think in 2007 Landcare Research (Ruscoe) did research on what happens in the years following an aerial drop of 1080 poison. It was found that rats that survived the poison drop and with much more food available, increased their breeding rate so that by one and a half years later (18 months) the rat population was back to where it was before poisoning.
Four years later, after the rat population resurgence continued, the rat population was something like 3-4 times original numbers.
Meanwhile during the rat population explosion, stoats who prey chiefly on rats, increased breeding and a population explosion of stoats ensued.
So DoC’s aerial 1080 drop stimulated upsurges in rat and then stoat numbers.
Really the poison drop achieved nothing of its aim to eliminate or at least control rodent numbers – instead it led to a population explosion of rats and then stoats.
So that was in 2007, so in 2020 what was new?
So can we conclude that the ever declining numbers of birds may be caused by something else then, like, maybe the indiscriminate use of 1080?
Why were Stoats and ferrets introduced into New Zealand?
It was obviously not because they prefer to eat birds.
They were introduced because their “dinner of choice” was and still is rabbits.
They also hunt and eat other species of rodents like rats and mice.
Just like any other species (including our own) these animals will hunt and eat other species if what they prefer is not readily available but birds are not their preferred “dinner”.
We “humans” prefer birds to rats, mice, rabbits or the other natural prey of Stoats.
Our emotional reaction to evidence that Stoats might eat birds overcomes the reality that they prefer to hunt and eat RODENTS.
We also have the ability to interfere with and manipulate nature instead of accepting the “balance of nature” that would occur without our interference because that gives us the illusion that we are IN CONTROL.
New species have always become introduced into existing ecosystems and either survive if they adapt or die off if they do not.
Stoats thrived because their preferred sources of food had also been introduced and thrived as well.
Now that “authorities” have decided to try to eradicate species that were desired and introduced by past “authorities” we have rejected the idea that natural balance can occur and decided that we should control the biodiversity as we decide.
This has created a dilemma.
If we reduce the stoat population, there will be more rabbits, rats and mice to feed the surviving stoats and promote their reproduction and survival.
If we reduce the preferred food sources, the Stoats will have to hunt and eat other “native” species to survive.
The Predator Free Ambition is evidence of our “human” desire to CONTROL “biodiversity”.
This control is theoretically achievable if enough resources can be diverted to achieving it.
The most necessary resource is the tax revenue that New Zealand workers generate from the production of valued goods and services. This funding can be either from current tax receipts or incurring debt that has to be services and repaid in the future.
The estimated cost of the eradication ambition was 9 Billion dollars but, as usual, it has increased to be over 18 Billion dollars and will continue to increase.
The money and other resources that are diverted to the Predator Free Ambition are not available for other uses that would be more beneficial to the people that have to work, earn and pay.
Resources diverted to this “ambition” are not available for things like education, medical services, infrastructure or innovation that would make New Zealanders better off.
We need to review and question this Predator Free Ambition objectively and rationally.
Is it working?
Is it practically achievable?
Does it have detrimental consequences?
Is it beneficial for the people that are paying for it?
Can we afford to pay for the escalating costs?
Is it even necessary or would the process of natural selection result in a more harmonious establishment of natural biodiversity FOR FREE?
“Saving the Birds” is emotionally appealing but AT WHAT COST?
Good article how ever I would love to know what birds are getting saves as the kea for example is decimated from 1080
Any idea where NewZealand is at with the biological control of pests Charlie?
Wow, nature is complex! So many loops and feedback loops and a matrix of connections that we have little understanding of. I empathise with the desire to “do good” but as with so many things, nature finds a balance all on its own – maybe we are better to dial down the big ticket glamorous careerist “conservation” projects and spend that money on feeding kids who go to school with no shoes?
Obviously by the above comments all are well aware of what’s going on why in hell can’t the DoC see that.
The same thing with possums. There’s at least three studies I know analysing possums’ stomachs. No trace of birds, feathers, eggs found, yet DoC and Forest and Bird make the possum out to be a predator. Misinformation! Jacinda Ardern needs to get her Ministry of Misinformation onto it.
It’s been known for years that stoats main prey is rats.