Facts about Powelliphanta snails

Giant land snail

Powelliphanta snails are not your common garden snail! In fact, they are totally unlike garden snails, which are a European import and an unwanted garden pest.

Powelliphanta are giants of the snail world. They can reach up to 90mm across, or the size of a man's fist.

They are also beautiful. Their oversize shells come in an array of colours and patterns, ranging from hues of red and brown to yellow and black.

And Powelliphanta snails are most unlikely to be found in your garden. Most favour living in the forest, and particularly like to eat earthworms, sucking them up through their mouth just like we eat spaghetti!

In fact, these meat-eating giants of the forest floor are true biological oddities. They are as representative of New Zealand's unique evolutionary history as the kakapo, moa or kiwi.

Unfortunately, they are also one of the most threatened of New Zealand's invertebrates. A total of 40 species or subspecies are ranked as being of national conservation concern.

Facts about Powelliphanta

• Powelliphanta snails are carnivores. Their favourite prey is earthworms, but they are also known to eat slugs.
• The largest species is Powelliphanta superba prouseorum, found in Kahurangi National Park and measuring about 90mm across. These are the sumo wrestlers of the snail world, weighing in at 90g, or the equivalent of a female tui!
• The genus was named after Dr A.W.B. Powell, a former scientist at Auckland Museum who studied the snails during the 1930s and 1940s.
• Powelliphanta snails used to be known as Paryphanta snails, until the 1970s. Now, Paryphanta refers only to kauri snails, which live north of Auckland.
• Powelliphanta snails are hermaphrodites, meaning they possess both male and female reproductive organs and therefore can mate with any other adult Powelliphanta.
• Powelliphanta snails lay about 5-10 large eggs a year. Each egg is up to 12-14mm long, pearly pink and hard-shelled - just like a small bird's egg!
• Powelliphanta are nocturnal. For the most part, they live buried in leaf mould or under logs, only coming out at night to forage and to mate.
• It is estimated that Powelliphanta snails can live up to 20 years. In snail terms, that is an incredibly long life span!
• Because Powelliphanta snails are prone to dehydration, they cannot survive in dry conditions. For this reason, they are more common in moist high-altitude forest than in drier forests at lower altitudes.

Where to find Powelliphanta

Snail distribution map

The stronghold for Powelliphanta snails is in north west Nelson and north Westland, where most of the species occur.

They are also found in the Marlborough Sounds and Mt Richmond Forest Park, as far south as Fiordland and Southland and, across Cook Strait, on parts of the Kapiti Coast and into the central North Island.

Different Powelliphanta species can be found from sea level, where they live in rich temperate rainforest, to above the bushline. Most of the alpine species have to contend with prolonged snowfalls and bitterly cold winters. The most likely sign of their presence will be empty snail shells on the forest floor.

Visitors will be unlikely to spot a live snail, except at night or occasionally on rainy days. They are most likely to be active on warm, moist nights after a long dry spell, when they will be out foraging for food.

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