“Powelliphanta appear to be “painted on the landscape” in a way which no other land snails in New Zealand are.”
Science Advisor Kath Walker has been studying Powelliphanta snails for nearly four decades and has recently submitted her PhD on this ancient lineage of snail – an awesome achievement to someone so dedicated to these quirky creatures, which are special to some of our most rugged and wild landscapes.
She says she feels a “sense of responsibility” to the snails, and a part of ensuring they survive this increasingly hot and crowded planet is to help tell their story…
What got you interested in Powelliphanta in the first place?
That’s a long, long time ago!
Being interested in Powelliphanta is all tangled up with the exhilaration of getting to know them and where they live. They live in native forest and tussock and the distributions of many were still only roughly known when I first came across them.
Just out of university nearly 40 years ago, my partner Graeme and I set out to visit them all to see how they were faring in the face of predation by exotic pests, and as their health depended in part on the size of their populations, we started trying to better define the range of each.
It became a tremendous spur to tramp into odd places, parts of the backcountry where few had bothered to go before. Unfortunately, Powelliphanta have a strong penchant for dense and wet kiekie, supplejack and leatherwood vegetation, so often the walking was not that pleasant, but there was that thrill of discovery.
As Stephen Jay Gould put it so eloquently while studying small land snails of the Bahama’s:
“It’s the unalloyed joy of finding something new”.
Putting together the connections between Powelliphanta species and their distribution across our country has been like piecing together a giant jigsaw puzzle. I tried to say as much in my thesis:
“Powelliphanta appear to be “painted on the landscape” in a way which no other land snails in New Zealand are. It is possible to identify just where a Powelliphanta has come from, from examination of its shell alone. In the bio-geographical patterns the morphological (and genetic) relatedness of Powelliphanta taxa make, the history of the last several million years of climatic, geologic and topographic change in New Zealand find a reflection.”
These guys are unique, and hugely interesting. Have you seen them eat? It’s intense! Check out this little one making a meal of a worm:
What did you learn about the diversity of Powelliphanta?
I learnt Powelliphanta are more than a pretty face! One of my chapters was called in part “appearances do matter” as one of the main questions was— are all those subspecies for real? Are the conspicuous differences between the shells reflecting genetic differences of some significance, or just different colours of lipstick?
Well, all that colour and patterning turned out to be important differentiation, genetically-based, and a reliable guide as to species. Just why the shell patterns are so flamboyant is probably related to its function as camouflage for a relatively large and conspicuous invertebrate.
What species is of particular interest to you and why?
It’s hard to go past Powelliphanta superba prouseorum, which is as superb and big as its name suggests. It’s the largest Powelliphanta and at 90 grams, an adult can weigh more than a Tūī.
It has an old-gold coloured shell with a white frill round its foot. It’s a magnificent beautiful creature, but on current trends, it’s doomed.
Although it lives in legally protected Kahurangi National Park, the population has been decimated by decades of predation by rats, possums and pigs, and climate change is now contributing to the soil moisture loss which deer, possums and pigs began.
Large old adults are now very rare.
It’s almost entirely unknown as it lives in the back of beyond and is a near-mythical creature, even to DOC-snailers.
Letting this subspecies fade away should be as unthinkable as losing the kākāpō, but it has no team of dedicated workers, no Facebook Page, not even a common name.
What was the most difficult aspect of the P. augusta situation for you?
That we were not generous enough to have left intact that tiny fragment of remaining snail habitat, when Stockton mine had already consumed almost the entire upper Stockton Plateau. And I could see the long dreary road ahead, which we are still on today, trying to keep a species without its habitat.
It was extra difficult that we were knowingly, unnecessarily, setting off down that path, when it was already clear that recovery of any species is incredibly difficult and expensive once populations are small, even when their habitat remains.
Besides, the place had got under my skin by then; the stunning sandstone escarpment of Mt Augustus was a spectacular landform, formed eons ago, deconstructed in mere months.
What have you gained the most benefit from by the captive rearing of P. augusta?
Learning much more about the biology of Powelliphanta than had previously been known; the specificity of the range of pH it could withstand, the timing of egg-laying and hatching, the ability to store sperm, its mating and feeding behaviour, its growth and breeding triggers, the natural life span of alpine Powelliphanta.
Do you think the public perception of our native snails has changed over time? For better or worse?
Probably a bit of both. The saga of the snails on Mt Augustus brought infamy in some quarters and increased interest in others.
In Nelson papers in late 2011 at the height of the saga, one story had a photo of Powelliphanta with the caption “unlikely celebrity; a Powelliphanta snail at home – a rare paragon of the environment”, while Peter Talley was quoted in another story attacking those “greenies” “who fabricated concerns for snails and seals”.
I really thought snails had hit the bigtime being mentioned in the same breath as seals, but most people remain pretty unaware what an amazing snail nation New Zealand is.
Unfortunately, the introduction to New Zealand of the common snail from Europe, which reach plague proportions here, destroying home garden vegetable crops, has probably forever distorted peoples view of snails.
Garden snails are a molluscan weed so it’s pretty hard to get past the idea that all snails are good for, is as French food. Still, although people only regularly see sparrows, they do seem to understand that there are albatrosses too, I hope we can get there with New Zealand’s native snails.
What is the one thing you most want people to understand about conservation of Powelliphanta that would aid in their recovery?
Keeping such a quintessential New Zealand animal as part of the landscape would mean we would also get to keep a great range of the wild places of New Zealand. Furthermore, protecting Powelliphanta means whole micro-cities of iconic New Zealand invertebrates could also thrive.
If we can stop the litter layer in our forests being trampled, compacted, desiccated and rooted by pigs, goats, deer and hares, and we can keep predation by rats and possums in check, many of the lovely invertebrates only older New Zealanders can now remember, would recover too.
The giant weevils and weta, peripatus and stick insects, huhu beetles and leaf-vein slugs, all need the same thing as Powelliphanta: that their homes are not turned into carparks or coal mines, and that the ecosystems in which they live regain their integrity.