“What we found out was that they were not having babies. They were mating, but they were not producing any offspring,” says Marquez-Mazlin.
They needed the rats to reproduce for their research. They soon worked out that a “naturally occurring compound” that the rats were being fed was causing their sterility.
“We never thought much of it because for us, that was a problem,” says Marquez-Mazlin.
It wasn’t until Marquez-Mazlin had relocated to New Zealand that he realised the significance of that “problem”.
“I was talking to someone who kept bringing up 1080, and I was like, ‘What is 1080’?”
After learning about New Zealand’s battle against multiple introduced species – and the lengths that authorities go to in order to slow their spread, Marquez-Mazlin realised he might have something to contribute.
“At that point, I had a bit of a flashback. I started going back into it and decided let’s do a proper study on this. A systematic study to see whether we can get this to be permanent or [understand] how long does it last? What concentrations would we have to use that were effective at sterilising predators? So, we did a trial with possums,” says Marquez-Mazlin.
He says the introduced mammals carry their own difficulties for researchers.
“With possums, it’s really hard to actually try to breed them in captivity. The other problem was that the first trial, they were all possums that we had captured from the wild, so they have different health histories. It was really hard to establish a baseline,” says Marquez-Mazlin.
Still, there was enough success to encourage further research.
“What we found out was we could make them menopausal. we could take a look at their ovaries and see what the damage was. [Which was] Like a much older animal.”
He says other than the early onset of menopause, the female possums were healthy and happy, while the males were “absolutely unaffected”.
“So then we decided, let’s move into rats. These are lab rats so we established a baseline on that and we started looking at what concentrations we could achieve sterility.
“We gave the compound in peanut butter to the rats. The ones that only had peanut butter had healthy babies. The rats that we treated with high and medium doses of the compound didn’t get pregnant at all.
“The ones with the low dose got pregnant, but they didn’t go to completion. That was really exciting,” says Marquez Mazlin.
They undertook two rounds of mating with no viable offspring in either.
“The other thing that is really exciting is that we were able to induce sterility without affecting their behaviour or their health at all. It doesn’t kill the animals, it just sterilises them.”
Another major pest problem in New Zealand is rabbits. Marquez-Mazlin believes that the compound could have a similar outcome with the ever-growing population of wild rabbits – and end the need to use the controversial calicivirus.
“With rabbits, we’re just looking based on their metabolic pathways and comparing that to rats and, and possums. So, we have some preliminary data for that, but there’s no one in New Zealand doing any rabbit studies,” says Marquez-Mazlin.
“We could potentially try to do it up in Europe or something like that, but it’s like everything, right? We’ve been doing everything on a shoestring budget.”
He says others have investigated sterility as a weapon against invasive species – but administering it has proven difficult.
“People try to use vaccines and stuff like that, right? The whole argument was that if you’re going to have to capture an animal to vaccinate it and then release it – maybe just put it down rather than release it again. Our approach is not a vaccine, it’s not a biological agent, it’s just a natural compound,” says Marquez-Mazlin.
Like 1080, the menopause-inducing compound would be delivered as a bait. That’s where the similarities with 1080 end.
“Obviously we know [that] while 1080 is really effective, it’s a horrible way to die. Whether you’re for or against it, the way that it kills, it’s not a nice way to go,” Marquez-Mazlin says, adding that another benefit is “no crossover contamination”.
“It’s not like 1080 that if you have a mouse that eats 1080, then there’s a risk that an owl will eat the poisoned mouse and then the owl will die.”
In fact, he claims his compound has no effect on birds.
“The compound is nontoxic to humans or to livestock or to dogs. Cats it might sterilise, which is also a good thing.”
Long-time 1080 opponent and current Waikato Regional Councillor Clyde Graf welcomed the research.
“A non-toxic, species-specific alternative sounds like a positive initiative,” says Graf.
Graf has spent more than a decade opposing the use of 1080 and documenting its impact.
“The 1080 poisoning programme to date has been, and continues to be, an ecological disaster. Declines in omnivorous and insectivorous birds in repeatedly poisoned forests continue to be realised,” says Graf.
“I tend to believe that the best alternative to 1080 poison being used is simply to stop using it.”
Department of Conservation (DoC) National Predator Control Programme’s Peter Morton told the Herald they weren’t familiar with the University of Canterbury project, so couldn’t comment on its potential effectiveness.
“DoC uses the most effective predator control tools available, such as biodegradable 1080 toxin and large-scale trapping, to protect the best surviving populations of vulnerable native species and forests. We are holding the line for our native biodiversity as we work towards the Predator Free 2050 goal,” said Morton.
“As part of the PF2050 programme, many new tools and techniques are being developed to take us closer to eradicating rats, possums and mustelids (stoats, weasels and ferrets) from Aotearoa New Zealand. DoC supports and welcomes these developments as they will be critical to achieving the Predator Free goal and enabling native species and forests to thrive.”
Whether or not Marquez-Mazlin’s compound is added to DoC’s toolbox will depend on the outcome of more research. Releasing the compound bait into a field trial will require appropriate approval but Marquez-Mazlin is hopeful of beginning that stage soon.
“I would like to have a trial by this coming spring.”
Mike Thorpe is a senior multimedia journalist for the Herald, based in Christchurch. He has been a broadcast journalist across television and radio for 20 years and joined the Herald in August 2024.
