Rescue a triumph for conservation

00:47, Jun 22 2013

Remember those rare snails, some of which froze to death a few years ago. Where are they now? DEIDRE MUSSEN finds out.

They're anything but a cuddly panda.

The kakapo would eat them for breakfast - as many miners not so long ago were tempted to.

But the famous meat- eating mahogany-coloured Powelliphanta augusta snails, famously rescued from their home above a West Coast coal seam seven years ago, have now become iconic conservation poster- creatures.

Shifting the newly discovered giant snail species was part of the deal with state coalminer Solid Energy for New Zealand's largest opencast coalmine, Stockton Mine, on Stockton Plateau, near Westport.

They were put into coolers at a new facility at the Conservation Department's Hokitika office for protection and monitoring.


By late 2007, about 4000 snails had been returned to two sites in the area. The rest quietly continued to reproduce in captivity.

In an important milestone, 443 captive-reared baby snails were freed two months ago into their home range at a site rehabilitated post-mining, which adjoined a small slither of their original habitat on Mt Augustus that was left unscathed and where some snails remained.

A second release of twice as many young snails is planned at neighbouring rehabilitated sites in spring.

Solid Energy, which initially predicted the snails would cost it about $6 million, pays $125,000 a year for the captive programme.

Its environment and health and safety manager, Mark Pizey, said the programme was always a "holding pattern" with the intention all snails would be returned to the wild.

Solid Energy had trialled vegetation direct transfer for the past decade, which involved diggers carefully scooping up soil, vegetation and invertebrates, shifting it to a new location largely intact before mining the area.

"It opened up the possibility of recreating their habitat in the area which they were first captured. That has become the principal focus for us."

Some of the snails' original habitat was moved about 800 metres north using the technique and snails have now been found alive, proving they could survive the move, he said.

Pizey, who admitted to becoming rather fond of the beautiful snails, said it was a unique project for an animal that could hardly be described as charismatic megafauna.

"If you're a panda, you get a lot of people saying 'Ooh, aah' and giving you money. If you're a flat worm or snail, it's much harder."

Early on, many people predicted keeping snails in captivity would fail miserably but instead, he said it had led to huge leaps in knowledge about the species and breeding success.

"I think it's undoubtedly raised the bar in terms of expectations of what could be done. There would have been an era where people would have said 'So there are snails, don't worry about it'.

"You can restore a site and reintroduce species back into it. We've proven the concept to DOC and the Environment Court is also aware of it.

"What may have become a fatal flaw in a project, now there may be the technology to resolve that conflict."

Pizey said the project had become one of the most distinctive challenges in his mining career.

"I didn't think when I became a mining engineer I'd end up working with carnivorous snails."

The department's captive snail project manager, Rodney Phillips, said the annual survival rate of captive snails was more than 90 per cent and those released had a 60-80 per cent survival rate.

The project had changed significantly over the years as knowledge grew.

Initially, snails were kept in separate containers. Some laid eggs, either self-fertilised as hermaphrodites but more likely from mating before their capture.

"The aim of the project was to keep the snails alive," Phillips said.

However, they started being kept in groups of up to six to boost the population, particularly after about 810 snails of varying ages froze to death when one of three coolers malfunctioned over Labour Weekend in 2011.

Last year, 1200 baby snails hatched.

The current population of about 2000 hatchlings kept their two part-time carers busy and forced the department to expand its worm farm at the Hokitika site, he said.

Each baby snail was fed four little worms a month and the 600 adults got six worms a month, a vast increase on one a month in the programme's early days.

The horde chew through 11,600 worms a month.

John Lyall, who leads the whole project for the department, said its true test would be whether released snails reproduced. The first babies from snails released in 2007 were expected to be big enough to find in about a year.

That was the predicted time for the freed snails to settle into their new terrain, lay eggs, which took about a year to hatch and then, for the slow-growing snails to reach a detectable size.

Phillips said it was very satisfying to release some baby snails back to Mt Augustus and looked forward to when all the snails were free. "They are like my babies. It was a Born-Free moment."


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