Powelliphanta Snails
Powelliphanta are giant snails but they aren’t likely to be found in your garden snacking on your lettuces.
Sumo Snail
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Powelliphanta grow up to 9cm across, the size of a man’s fist, and weigh about 90grams. Other giant snails in NZ include the Kauri Snail and Flax snail.
They are only found in New Zealand and they are carnivores, which means they love to eat meat. They slurp up worms and slugs at night. They also live a lot longer than your garden variety snail. Some can be up to 20 years old!
Powelliphanta are nocturnal and hide under the leaves on the forest floor where it is damp and dark during the day. If they don’t have damp places to hide in they would shrivel up and die in the sun.
Powelliphanta have babies by laying eggs. Most snails lay hundreds of eggs but Powelliphanta only lay 5 to 10 eggs each year. The huge eggs have a hard shell, just like a bird’s egg. Because Powelliphanta can live so long and used to have fewer enemies, it didn’t need to have lots of babies.
Why worry about a snail?
Powelliphanta are becoming rare. In the 1800’s and 1900’s humans destroyed a lot of the forests where Powelliphanta were found. This means there are only a few places were Powelliphanta can live around Nelson, the West Coast of the South Island, the Kapiti Coast and in the Wairarapa
Shell Jewelry
Powelliphanta have shiny, patterned shells that can come in all different colours – red, brown yellow and black. Until 1982 people were allowed to collect Powelliphanta shells. Now people must leave the shells where they found them so the calcium in old shells can be used by the snails to make their own shells strong. Snails absorb the calcium from the ground, and that’s the way they make their shells.
Like many of New Zealand plants, animals and insects, Powelliphanta are also under attack from introduced predators. Their natural predators are weka, which peck a hole in the side of the snail’s shell and eat the snail inside. Introduced predators include possums, rats, pigs and sometimes thrushes and hedgehogs will eat them as well.
Possums only learnt to eat Powelliphanta in the 1970s but since then they have become a serious threat to these unique snails.
>>One possum can eat up to 60 adult snails over a couple of nights. In some cases possums on one side of a large river kill snails, while possums on the other side of the river don't. Why? Because they haven’t learnt how to get into the shells.
The Department of Conservation controls rats and possums by trapping or poisoning them in places where Powelliphanta live.
