Senior Sergeant Tony Woodbridge of Oamaru police said yesterday some search and rescue teams who had worked over the past two days had been stood down from the search in the Ahuriri Valley near Omarama, but that did not constitute a scaling down of the operation, as there were six teams still in the field.
Up to 60 personnel were now involved with the search after the arrival on Tuesday evening of a NZ Fire Service command truck, along with an RNZAF Iroquois helicopter and seven army personnel, Mr Woodbridge said.
Although originally the search focused on a 200sq km area in the vast Ahuriri Valley Conservation Park, searchers yesterday reduced that to a more specific area of the Dingleburn Track following a sighting of the missing 53-year-old on Saturday morning.
Senior Sergeant Jason McCoy said SAR teams on the ground had been doing a foot search, aided by Search and Rescue dogs.
By yesterday, Mr Palmer had been missing for four nights. New Zealand Mountain Safety Council bushcraft programme manager Chris Owens said that although he did not know how well provisioned Mr Palmer was, it would still be possible for the University of Otago librarian to survive for several nights, even if he was only lightly equipped.
"If anyone is compromised, we would suggest that they stay still rather than keeping on the move. It is much easier for search and rescue people to locate anyone that way.
"We advise that they get some sort of shelter either they find one like a little rock bivvy or create one with rocks around them and use, fern, punga, whatever they can."
Staying out of the wind could also prove vital to survival.