A successful trial of deer repellent used with aerial drops of 1080 poison would add another tool for possum control, this week’s Environment Waikato Biosecurity Committee meeting heard.
Pest control company EPRO Ltd reported on their Animal Health Board-sponsored trial of various control methods on a Kaimanawa forestry block at Hatepe near Taupo over the winter. The trial used 1080 in bait stations, Feracol bait in bags, Feratox and trapping, the contractor’s choice of method (Feratox, traps and dogs) and aerial 1080 carrot baits dropped with a repellent added.
The methods were used in four blocks, each divided into five sectors to test each method, and included remote and difficult country. Epro Ltd Operations Manager Cam Speedy said the area was one of the most used areas for hunters in the country and the treatments covered a range of habitats.
Before the trial began trapping was done to establish base possum numbers, with 800 caught in soft traps and released. The effect on rats was also assessed.
Four of the tests took between 77 and 140 days to complete at a cost of between $37 and $43 per hectare, with a post operation trap catch of between 1.32 and 3.54 percent. Some methods had little effect on rats.
Aerial 1080 took eight days at a cost of $20.25 per hectare without deer repellent and $26.25 with repellent. Residual trap catch was 0.17 percent and no rats were found alive. Five dead Sika deer were found, despite the repellent use.
Mr Speedy said 1080 was clearly more effective but created ill feeling for hunters because of the potential effect on their dogs and deer. Deer hunters publicised considerable misinformation about the dangers of 1080, including effects on water and that it caused cancer. However the repellent was untouched by deer for six days and gave the deer some protection, as many were seen alive in the poisoned area.
“The by-kill (of rats, mustelids and deer) can have conservation and Tb benefits, but the opposition it creates threatens our access to this tool,” he said.
The use of repellent did not affect bait toxicity for possums and there was no effect on native birds. It clearly repelled farmed deer, and it was planned to test it on cereal pellet bait. Mr Speedy said using repellent would be useful where deer by-kill was a block to 1080 treatment, although deerstalkers were adamant that aerial 1080 drops should not be used.