A Department of Conservation spokesman said Doc was aware of and supported the placement of the sign, in order to advise as many people as possible entering the area at that point with dogs, for which the poison is potentially deadly.
About 16,500ha in the Manorburn area was being covered in the operation. It was being directed by Ospri New Zealand and was part of the national TBfree programme to eradicate tuberculosis, Otago Pest Services Ltd manager Jim Hughes, of Cromwell, said.
A sign in Alexandra about the operation is just past the old road rail bridge. It warns people not to touch the bait, to watch children at all times, and that poison baits or carcasses are deadly to dogs.
The sign also says no poison has been laid on or near the trail, and it is "up the hill only".
Mr Hughes yesterday clarified the poison started being laid about 200m from the trail, "up on the hill towards the clock". The operation started on May 28 and all the poison had been laid.
The operation covers land around the lower and upper Manorburn, and private land on Matangi Station and Little Valley Station. All landowners and the Central Otago District Council had signed off on the operation, Mr Hughes said.
He said the poioning was to help eradicate tuberculosis. While some of the Manorburn area was "very clean" without evidence of tuberculosis, other areas were "diabolical".
A mix of baits was used and some trapping was being done.
The two types of bait are Feratox cyanide and cyanide. The Feratox is one small capsule (about the size of a small pea), placed into about a tablespoon of brown peanut butter and put into a small blue bag or bait station and stapled to trees about 50cm off the ground, or above stock height in areas where there is stock. The cyanide is used in paste form — baits are generally located on tree stumps or roots, logs laying on the ground or rocks. All toxic baits are dyed green.
Mr Hughes said the official time period for bait to remain toxic before it disappeared and decomposed was four months. However, if there was rain or snow it could be gone within two months.
He said the actual capsules were not considered dangerous to dogs as it was not possible for them to bite into the hard plastic outer. The danger to dogs was eating poisoned carcasses, in particular the heads of possums. He knew of three dogs to die in the past 11 years, one in Central Otago and two in Dunedin, and all had eaten the heads of poisoned possums.
He said poisoning was last done in the Manorburn area three years ago and again two years before that.
About 400 possums had been killed so far during this operation, and about another 100 were expected in the next week. Some would be tested for tuberculosis, Mr Hughes said.
