This blog post was written by postgraduate student Thomas Agnew as part of the course, Research Methods in Ecology (Ecol 608). Thomas revisits a Lincoln University research area on the use of toxins for possum control published since the early 1990s.

Signs of protest against DOC controlled 1080 drops

The 1080 (Sodium Fluoroacetate) debate has reared its ugly head once again. Articles just weeks apart in common New Zealand media suggests that Kiwis are more aware than ever of the threat posed by pesticide and toxin applications in natural environments. Department of Conservation plans to aerially apply 1080 to forested land in Wainuiomata (Dominion Post, 08/05/2012) and Golden Bay (Nelson Mail 03/05/12)have been met with fierce opposition. Those opposed to controlling possums with the use of 1080 desire a highly selective, humane control method, with little effect on non-target species and domesticated animals, which they feel 1080 cannot claim. As our science and technology advances, new and improved methods for controlling possums and other introduced mammalian predators arise, some show promise, whilst others fade away. It is often difficult to tell whether we are making progress when it comes to pest management in New Zealand. Whilst the debate between supporters and disapprovers of 1080 rages on, I set out to investigate whether the turn of the century has meant improvement for our most loved and most hated toxin.

In 1992, Charles Eason of Lincoln University published a paper evaluating the appropriate alternatives to 1080 use for possum control1. It highlighted not only the need to develop a socially acceptable chemical product, but also the need to avoid bait shyness and resistance build up towards 1080. The focus fell with non-anticoagulants, such as Cholecalciferol and Nicotine. Within the article, Charlie explained how the lethal doses for both male and female possums for these substances had already been established, and that the next step in finding an alternative to 1080 was getting non-anticoagulants into palatable bait types at a cost effective price. I feel that this paper best represents the 1990’s scientific viewpoint of finding an alternative toxin to 1080. With that in mind, have we seen the advancements in possum control technology that Charlie suggested back in 1992?

20 years down the track, and we are still commonly debating the pros and cons of 1080 use in New Zealand, as shown by those articles mentioned above. It remains at the forefront of our nationwide attack on possums, and it doesn’t seem to be disappearing anytime soon. Just two years ago, Charlie Eason was again the lead author in a modern review of the toxicology and efficacy of 10802. This paper was an overall review of the modern day 1080 toxin, which compared it with other common toxins (including the aforementioned Cholecalciferol) for various aspects such as environmental persistence, ability to bioaccumulate, and effectiveness for killing possums. Compared with the other options, 1080 proved to have a relatively low half life, and an average level of bioaccumulation. It still proves to be one of the most potent (if not the most potent) chemicals for causing fatalities amongst possums, and acts at one of the lowest concentrations. Brodifacoum is the new kid on the block. This anticoagulant was absent from debate during the 1990’s, and it now opens up a whole new can of worms. It is a slow acting toxin, as it takes up to 14 days within the animal before any adverse effects begin. It is this form of pesticide that will fix our problem with bait shy and 1080 resistant possums. Off course, Brodifacoum doesn’t come without its own issues. It is less selective than 1080, remains in the environment for much longer, and has the potential to bioaccumulate.


1080 :  a poisoned possum displayed alongside a deceased tree weta


In my personal opinion, the aerial application of 1080 is not the perfect option, but it is the best one available to us at this time, and has been so for the last 20 years. Any attempt to introduce “new and improved” chemical products to control possums in this country will always be met with heavy competition (which I also believe to be healthy), and biological control seems to still be a fair way off. To expect those who protect our native species and our agricultural industry to control possums without an effective chemical product is, to me, outrageous. Our climate and terrain is such that labour intensive methods such as shooting and trapping cannot possibly be expected to make a significant enough impact. It is my opinion that those looking to improve the 1080 poison need to address the concerns of the general public and hardcore greenies, by making domestic animals, waterways and endangered species less susceptible to intoxication. Perhaps when this is achieved, both sides can work together in an attempt to eradicate what is arguably the worst pest in our forests.

For more on possums have a read of this, this, this and this.
References
1 Eason, C. (1992) The evaluation of alternativetoxins to sodium monofluoroacetate (1080) for possum control, Proceedings of the Fifteenth Vertebrate PestConference.
2 Eason, C., Miller, A., Ogilvie, S.,Fairweather, A. (2010) An updated review of the toxicology and ecotoxicology of sodium fluoroacetate (1080) in relation to its use as a pest control tool i
nNew Zealand, New Zealand Journal of Ecology, 35, 2011.