Endangered giant snails that suck up earthworms like spaghetti are living in a small colony in Khandallah. Curator Invertebrates Rodrigo Salvador tells us more.
The giant snails of New Zealand belong to the genus Powelliphanta and there are several different species throughout the country.
Despite the name, they are not related to the South American giant snails (genus Megalobulimus, a.k.a. megasnails) or the African giant snails (genus Achatina). Rather, they belong to the family Rhytididae, with relatives in Australia and South Africa.
The kiwi snails are, in fact, only modest giants. Their shells can reach up to 9 cm in diameter, which is large for a land snail. But the shells of African and South American snails can easily surpass the 15 cm mark. Even so, the Powelliphanta snails are a sight to behold.
They are long-lived animals (at least 20 years) and, contrary to the majority of snails, are carnivorous. They feed mainly on earthworms and slurp them like strands of spaghetti.
Watch a giant snail dine on an earthworm in this video from BBC Earth’s Wild New Zealand, narrated by Sam Neill:
A threatened species
Unfortunately, all Powelliphanta species in New Zealand are vulnerable or threatened to some extent. They are legally protected, but their conservation has a checkered past.
However, a curious case of conservation happened in Khandallah during the 1940s which isn’t widely known.
Moving to Khandallah
In the 1940s, one subspecies, named Powelliphanta traversi latizona, was confined to a few forest remnants in the southwestern portion of the North Island.
Its critical status seemed to have worried a Mr. A.C. O’Connor, who in 1944, translocated 40 snails from Greenaway’s Bush near Levin to Khandallah, Wellington, which at the time lacked giant snails.
This translocated population spent some years in obscurity, until in 1984 when it was reported there were still snails in Khandallah.
That report gave the Khandallah snails a low conservation priority compared to other localities, but remarked some protection was necessary. Even so, they were forgotten once more. They have been mentioned in the Greater Wellington Regional Council’s ‘Ecosystem Plan’ of 2015, but only incidentally.
In any event, it is surprising – in a good way – that the snails in Khandallah are still around.
They survived largely unnoticed for over 70 years in a recreational area where people, rats, and possums are out and about.
This might mean that the species is rather low-maintenance for conservation purposes, which could allow easier development and execution of plans to preserve it. For instance, Zealandia has a similar terrain and established forest cover – not to mention a predator-proof fence! – and could be the ideal refuge for the Khandallah snails.
If you want to see the story in more detail, take a look at the article in this year’s IUCN newsletter, by Phil Parkinson, a volunteer at Te Papa, and myself.