Pests impede deer repellent trial

Otago Daily Times

04-06-2025

Possums are interfering with a trial to find out if white-tail deer avoid bait laced with a deer repellent.
The trial, taking place on Stewart Island, is designed by Manaaki Whenua — Landcare Research, which will analyse the data while Zero Invasive Predators (ZIP) staff do the field work.
Non-toxic cereal bait, with and without deer repellent, is being placed in front of trail cameras to observe how white-tailed deer interact with it.
The trial is being carried out on public conservation land at Halfmoon Bay.
Last year, the Department of Conservation (Doc) announced plans to drop 1080 cereal bait to reduce the feral cat population endangering the southern New Zealand dotterel/pukunui on Stewart Island.
About 43,000ha of Rakiura National Park will be poisoned between June and September.
The park, including bookable hunting blocks, will remain open during the operation but bait laced with deer repellent will be used within bookable hunting blocks only.
ZIP operations director Duncan Kay said progress in the trial had been slower than expected, due to the thriving population of possums on the island.
"They seem to be faster at finding these baits than the deer, reducing our chances of recording deer interactions."
The trial, requested by hunters, aimed to find out if deer repellent reduced the impact of aerial 1080 on Stewart Island's white-tailed deer population, Mr Kay said.
It would also show if adding deer repellent reduced the effectiveness of 1080 cereal bait on key target species such as ship rats, Norway rats and kiore.
So far 20 deer had interacted with the bait and none had eaten it, Mr Kay said.
"We need to record at least 100 interactions, where a white-tail deer approaches close enough to see and smell the bait, to form a statistically meaningful data set."
The trial would continue until sufficient data was collected, which could take several more months, he said.
A second trial would run during the aerial 1080 operation, when bait containing deer repellent would be dropped in the bookable hunting blocks.
Deer repellent had been used in aerial operations elsewhere in New Zealand and had been shown to reduce impacts on deer species including red deer, he said.
It is estimated the six-year Predator Free Rakiura project to eradicate pests will cost between $85 million-$90m.
New Zealand Deerstalkers Association president Callum Sheridan said his group advocated for the use of deer repellent in all 1080 bait.
"The excuse is there is not enough budget for it."
Each year the association met groups, including Doc, which planned to use aerial 1080 poisoning to discuss where deer repellent would be included in bait drops.
However, the area where deer repellent was used was very small compared with the total area where 1080 was dropped, he said.
"You would think it was a public safety risk, especially in the areas where people are going to harvest game meat, that you would just put deer repellent in it as a matter of course because that's the intelligent thing to do."
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