Huge by-kill of brodifacoum poison
I don’t live in Nelson so dropping 26.5 tonnes of brodifacoum poison into the Brook Waimarama Sanctuary won’t affect me
directly, but I care a lot about New Zealand wildlife. I'm the Waikato Regional Councillor for Taupo-Rotorua, and the
current Chair of the Environmental and Services Performance Committee.
ACRE, a group that advises Waikato Regional Council, asked councillors to look into our use of brodifacoum during our
last Long Term Plan. They were concerned about the bio-accumulation and persistence of brodifacoum in wildlife, and the
implications for our food chain. Our EPC Chair at the time, Clyde Graf, agreed to a review.
We invited Penny Fisher, a scientist at Landcare Research to give us readings about brodifacoum and other
second-generation anticoagulant rodenticide residues in wildlife. She did a teleconference with our committee; We
gathered information from other councils and government agencies and we looked at what’s happening overseas.
A lot of the New Zealand data about brodifacoum by-kill concerned me:
The entire western weka population was exterminated in a brodifacoum drop on Tawhitinui Island (1984); Nearly 60% of the
Tawharanui Regional Park dotterel population died through eating brodifacoum baits and poisoned sand-hoppers (2004);
Brodifacoum residues continued to be found in wildlife more than 24 months after the brodifacoum poison drop in and
around the Rotoiti Nature Recovery Project in Nelson (2005); The Rangitoto and Motutapu Island eradication by-kill
included dolphins, penguins, fish, numerous dogs and birds. Vast numbers of dead mussels washed up on Waiheke Island up
to five months after the poison drop. Hundreds of dead birds also washed up on Coromandel Peninsula beaches in the
months following (2009); More than 10,000 seagulls were killed in Shakespear Regional Park (2011);
Blue cod, mussels, limpets and birds had brodifacoum residues in them after the Ulva Island drop, prompting restrictions
on harvesting. Dead robin nestlings on the island were found to have brodifacoum residues, indicating that poisoned
invertebrates had been fed to the young birds. Nearly 90% of the weka population was also killed (2011); Brodifacoum and
other anticoagulant residues were found in freshwater fish, eels and sediment in Southland (2012); After Great Mercury
Island was poisoned, 16 dead seals and a multitude of birds and fish washed up dead on Coromandel beaches (2014); A
Landcare Research study of road-killed harrier hawks revealed 78% of those tested had at least one anticoagulant
rodenticide in them. Some had as many as four different types. Brodifacoum was common.
It’s dangerous stuff, no doubt.
I asked Auckland Council for the results of their monitoring of feral pigs on islands in the Hauraki Gulf. The reply
stated that 13 out of 14 pigs tested positive for brodifacoum residues. Brodifacoum has now been confirmed in fish,
shellfish, pigs, bats, deer, eels and birds across New Zealand, which is a concern for those who hunt and fish. There’s
also concern for those who commercially harvest wildlife. MPI notified a restricted procurement area for feral pigs in
Marlborough due to high levels of brodifacoum residues in pig livers in 2004.
Why would we use brodifacoum when our own scientists have expressed concern about residues persisting in the
Penny Fisher said in 2013 in her Overview/Summary – Environmental Residues of Anticoagulants Used for Pest Control, 10
“There is increasing evidence that uses of anticoagulants for both household rodent control and field pest management
are resulting in widespread contamination of both terrestrial and aquatic wildlife. The latter is presumably through
carcasses of poisoned animals entering waterways ….”
According to MPI, brodifacoum is the most inhumane toxin we’ve got, causing pain and suffering for days to weeks before
an animal succumbs to internal haemorrhaging. Apart from the lethal effects, brodifacoum also causes sub-lethal
reproductive and developmental damage. Would you choose to use brodifacoum if you knew it was also going to harm and
kill the native species you’re trying to protect?
Personally, I'd prefer to find another method of pest control that’s acceptable to the Nelson community. There are
plenty of alternatives.
Kathy White is the Waikato Regional Councillor for Taupo-Rotorua and the current Chair of the Environmental and Services
Performance Committee. This is her personal view.