A whale rescue expert is dumbfounded conservation department crews weren't stationed earlier at the site of today's mass stranding at the top of the South Island.
A stretch of one of the country's most beautiful beaches has become a graveyard as more than 300 pilot whales lie dead on the sand. The remaining 100 who survived the night are at the centre of a major rescue operation which is now likely to stretch into the weekend.
The Department of Conservation (DoC) said it received a report a pod looked like it might beach at 8pm yesterday.
Project Jonah and the local community were alerted about the possible stranding and scores of volunteers were mobilised at first light to try to save the stricken mammals.
Today DoC Golden Bay Operations Manager Andrew Lamason defended the response, saying staff did not arrive at the site until 5.30am because it was too dangerous to work with whales at night.
But former New Zealand Whale Rescue co-ordinator Steve Whitehouse, who has attended more than 2000 strandings, said that was nonsense.
"I can honestly say I have been out there hundreds of times at night.
"Like anything there is a danger but you can mitigate the risks and if you know what you're doing and you know the risks you can work towards it."
Meanwhile, scores of rescuers are preparing for the long haul as they wait to see if any of the surviving pod has managed to make it out of the spit after this morning's high tide.
Lamason said it appeared the refloated whales were swimming in the wrong direction and heading back into the bay.
He said they would not have another chance to refloat the whales until tomorrow's high tide as it was considered too dangerous to try a rescue at night.
In the meantime, volunteers would help DoC staff care for the stranded whales throughout the afternoon and do whatever they could to keep them comfortable, he said.
Dr Stuart Hunter of Massey University is travelling to Farewell Spit to perform a necropsy on some of the whales.
"We want to try and determine if there's an underlying reason why such a large number of whales stranded and died in such a short space of time," he said.
"It's not unusual for pilot whales to strand en masse but this stranding is unusual due to the sheer number of whales involved and in such a small amount of time. So our goal is to try and understand if there's an underlying reason for this.
"Pilot whales are well insulated with blubber, so they will decompose very quickly, which means we need to perform necropsies as quickly as possible."
A necropsy involves examination of the internal organs to look for signs of infectious disease and trauma, he said.
"Ideally we will take small samples of the internal organs to examine under the microscope to determine what further tests should be undertaken.
"It's difficult to say when we'll know for sure, but it's likely to be weeks rather than days."
At the scene, hundreds of people have responded to a call for volunteers.
Collingwood Area School students have also helped in the rescue effort to refloat the whales, while some have sung a waiata to the animals.
The Interislander ferry this morning offered free passage on its afternoon sailings for certified marine mammal medics headed to the rescue operation.
Project Jonah said 75 per cent of the whales were dead when rescuers arrived at first light.
The whales had stranded on the inside beach of Farewell Spit, 1km from Triangle Flat, near Puponga.
It's the third largest recorded whale stranding in New Zealand since the 1800s. A thousand whales were stranded on the Chatham Islands in 1918 and 450 in Auckland in 1985.