A new toolbox toxin that can take out an elephant

Whilst hiking in Arthur’s Pass, there is always one plant that never fails to catch my eye. I notice it, not because of its’ beauty or its phenomenal size, but because of the alarm bells that go off in my head when I see it. This plant is Coriaria arborea, or tutu, and is poisonous to those that consume it. But could it be a game-changer for predator control in New Zealand?

Inspired by the paper by Shaun Ogilvie and his colleagues, ‘Investigation of tutin, a naturally-occurring plant toxin, as a novel, culturally acceptable rodenticide in New Zealand‘, I might have to change my alarm bells to something more celebratory and hopeful. Tutu and its natural toxin, tutin, could be a socially and culturally acceptable alternative to 1080 that we have been looking for. Ogilvie explores the potential of tutin as a mammalian pest toxin and is a good example of mātauranga Māori (Māori knowledge) and western science working together to create more widely accepted predator control tools.

Why do we need culturally accepted toxins for predator control in New Zealand?

Human arrival in New Zealand brought 31 species of mammals that were not present before humans. These mammals have negative impacts on both the economy and native biodiversity and for that reason they have been classified as pests. The ‘toolbox’ is a term used to describe the variety of methods available for the control of these pests. The toolbox highlights the necessity to have and use the most effective tools for the problem at hand.

Coriaria arborea, or tutu with fruits. Jon Sullivan (CC BY-NC 2.0)

Sodium Fluoroacetate (also known as 1080) is a toxin that is applied aerially and in bait stations and is currently a key part of the predator control ‘toolbox’. However, during the New Zealand Environmental Risk Management Authority (ERMA) reassessment of 1080 cultural concerns were raised by Māori around the use of 1080. This led to recommendations to continue research into culturally acceptable alternatives.

What makes tutin more culturally acceptable than 1080?

To understand what is acceptable culturally, you must first understand the Māori worldview and how it shapes their approach to kaitiakitanga (environmental guardianship). The spiritual connection between Māori (the indigenous people of New Zealand) and their whenua (land) is vital to explaining why tutin differs to 1080 in cultural acceptability as a toxin for predator control in New Zealand. For Māori, everything is connected through whakapapa (genealogy) to Papatūānuku (earth mother). Māori believe that all living and non-living things are connected and that maintaining balance between these things is vital for Māori well-being and survival.

Both tutin and 1080 are naturally found in plant species in New Zealand, however, fluoroacetate, the main ingredient in 1080, is more commonly found in plant species overseas where it is a defence against grazing animals. Tutu and its toxin, tutin, are native to New Zealand. Through a Māori lens, tutin connects back to Papatūānuku and therefore does not affect the balance between living and non-living things. 1080, though it has been found in low amounts in puha (Sonchus spp.), is not strongly supported by Māori communities as it is seen to be less connected to Papatūānuku and therefore, negatively disrupts the balance. Tutin being more connected, through whakapapa, to the environment it is being used in is what makes it culturally acceptable in comparison to 1080.

How poisonous is tutu?

Poisonous enough to kill an elephant.

Mollie was a young elephant touring New Zealand with the Bullen Brother’s circus company during the 1950s. She was a star of the big ring and the cause of much excitement during her visit to Ohakune back in 1957. Whilst grazing along the banks of the Mangowhero River, Mollie consumed some tutu and passed away. Mollies passing is still remembered to this day in the small town of Ohakune with the town recently erecting a plaque in Mollies memory.

Tutu taking the life of an elephant is quite phenomenal. However, when it comes to rodents, tutin has been found to be an effective and humane rodenticide at a dose of 55 mg kg-1. Tutin at this dose killed rats within half an hour on average and they tended to have shorter period of consciousness before death. In comparison, 1080 takes up to 10 hours on average to have the same effect and has a longer period of consciousness when compared to tutin. Lead researcher, Dr Shaun Ogilvie said in an interview that “at this dose, tutin could be considered more humane than all other presently available rodenticides in New Zealand.”

Is tutu a practical and culturally feasible rodenticide?

I’m afraid there is no straightforward answer to this because research on tutin as a rodenticide is still in the early stages. For tutin to be considered feasible in the field it must be both efficient and safe. Further research must take place for this to be known.

What boxes does tutin need to tick to be considered both safe and efficient as a rodenticide?

  • Targeted at rodents
  • Palatable to the target species
  • Effective against all individuals, regardless of sex or age
  • Unlikely to cause bait shyness
  • Unlikely to cause secondary poisoning
  • Humane to the target species
  • Allows enough time to diagnose non-targets who have consumed the toxin
  • Has an antidote
  • Is non-persistent in terrestrial and aquatic environments.
Agrocybe parasitica, or heart rot fungus on a tree. Petra Gloyn (CC BY-NC-ND 2.0)
Where do things go from here?

Many of the elements in terms of efficiency and safety are yet to be tested on tutin. Specifically, more work needs to be done on tutin’s palatability and ability to be sensed by rodents. Further research also needs to take place on bait shyness, secondary poisoning and the methods used to incorporate a stable, lethal quantity of tutin into a bait.

The final missing piece in the tutin puzzle is an antidote. However, mātauranga Māori may have an antidote in the form of Agrocybe parasitica, or heart rot fungus. This antidote would need to be explored later in the development of tutin as a predator control toxin.

Tutin has proven its effectiveness against elephants, although since they don’t seem to be a big problem in New Zealand, its potential for use on rodents is exciting. As you can see, there is a bit of work still to be done to explore tutin’s potential as a culturally acceptable toxin for mammalian predator control in New Zealand. I think this is a space worth watching as more tools in the toolbox can only be a good thing.

The author Jodanne Aitken is a postgraduate student in the Master of International Nature Conservation taught jointly at Lincoln University and University of Göttingen. She wrote this article as part of her assessment for ECOL 608 Research Methods in Ecology.

Leave a Reply