1080 drop queried as rats recover
Questions are being raised over the success of the Battle For Our Birds 1080 operation with some community pest groups still dealing with high rat numbers.
Anglers are also asking if setback zones have been removed from large remote waterways, despite the United States 1080 manufacturer's label stating the poison should be kept out of water.
However, authorities say the 1080 operation last year effectively knocked down rat numbers, and waterways that don't supply drinking water have never been excluded from drops.
Peter Adams, of Kahurangi National Park's Friends of Flora, said volunteers now faced "dynamic" rat numbers and apparent low knock-down rates in some areas of the group's 10,000-hectare range.
"Rat numbers on certain [trap] lines are coming down, but we are getting big kills on other lines."
Two adjoining blocks in the group's area were poisoned during the operation two months apart. It was thought the surviving rats re-invaded between the blocks, Adams said. In addition, the low concentration of poison used in the northern sector of the Flora was thought to be behind another low kill rate, he said.
With stoat and rat numbers beginning to climb and the amount of food still available Friends of Flora planned to meet with the Department of Conservation soon to talk about further possible control, he said.
Chris Petyt, of Friends of the Cobb, said he had not seen a great reduction in post-operation rat numbers. "We trapped the lower Cobb on December 30 and from 220 traps got 43 rats, which was more than we hoped for.
"Volunteers expected to catch some rats post-operation but not that number. It's very disappointing and we haven't had any reasonable explanation."
Golden Bay 1080 opponent Bill Wallace said the removal of predator stoats and food competitive possums through 1080 operations opened a window to 100 per cent survival for breeding rats.
A 2006 Landcare research study found post-1080 possum numbers were significantly lower and rat numbers significantly higher for at least one breeding season during the three years after possum control.
Wallace said rats have been in New Zealand for the last 700 years at least and stoats for the last 150. Yet bird populations in untreated areas, like the Tasman Wilderness Area and in parts of Fiordland, had survived.
DOC's rat counters, whom Wallace flew into the the Tasman Wilderness Area last April, reported being kept awake by kiwi call and followed by kakariki in the bush. "They were stunned by the birdlife, they had never encountered anything like it when working in previously poisoned valleys," Wallace said.
The Tasman Wilderness Area was one of the country's last biodiversity control sites, where 1080 had never been used. It should never have been poisoned, he said.
"But DOC had so much money for 1080 they didn't know where else to spread it."
Wallace said he did not back doing nothing, but the money could have been used far more wisely and effectively.
However, DOC Westport conservation services manager Bob Dickson said rat tracking levels have fallen from a high of 90 to 98 per cent in parts of Kahurangi National Park to an average of 3 per cent.
Specifically rat tracking levels had fallen to 13 per cent in the Waingaro from an August high of 78 per cent; to 32 per cent in the Cobb from 51 per cent; to 0 per cent in the Oparara from 63 per cent and to 9 per cent in the Wangapeka-Gibbs from 40 per cent.
He said while there were risks to native bird populations from 1080, overall improved nesting success through the subsequent lack of predators offset those losses.
Meanwhile, Nelson-Marlborough Fish & Game ranger Lawson Davey believes 1080 exclusion zones around some backcountry Tasman rivers and lakes were lifted for last year's aerial 1080 operations.
The West Coast Regional Council lifted restrictions to applying the poison to waterways nine working days after TB Free NZ made its application.
Tasman District Council spokesman Chris Choat said no 1080 exclusion zones ever existed around rivers and lakes that do not supply public or private drinking water.
But Davey said if no setbacks over backcountry lakes and rivers ever existed it raised questions around compliance with the Environmental Risk Management Authority's approval for the use of 1080.
This takes into account the poison's use being in line with the manufacturer's label which states it is ecotoxic and advises measures be taken to minimise 1080 from entering any body of water.
Choat said 1080's interaction with waterways was covered by recent science and advice on its use near rivers and lakes.
Davey said until now Fish & Game's greatest concern had been about the use of 1080 over game bird sites and the risk to hunting dogs.
Now, after 1080 pellets and a pre-feed was dropped near anglers in the Mokhinui and Wangapeka rivers last year, he wanted DOC to inform Fish & Game of operation dates, so it could in turn warn anglers.
Davey said the more he researched 1080 the more concerned he was about its potential long-term sub-lethal effects. Published international research raises questions around the poison's effect on reproduction rates.
Openly applying the poison over water only increased the risks, Lawson said.
In relation to the use of 1080 over waterways, Dickson said Tasman District Council consents had never required buffer zones around waterways that were not used for drinking water.
An existing WCRC 10-year consent, held by DOC was varied to allow the application of 1080 over waterways to bring it into line with Tasman's rules.
"Not excluding waterways and water bodies is not driven by cost. The concern is to ensure effectiveness of the control," he said.
Reinvasion from or through excluded areas can see pest populations increase quickly.
Dickson said research done by the Cawthron Institute last year, and referred to the Ministry for Primary Industries, found 1080 levels in trout force-fed the poison did not breach international health standards.
Wild trout caught from 1080 areas would not pose a food safety risk to humans, he said.
- The Nelson Mail