New Zealand's Giant Snails Are Unexpectedly Fearsome Predators

Slurp. The earthworm didn't stand a chance. BBC Earth via YouTube

We don’t give snails much credit. They’re small, slimy, and innocuous for the most part, so unless they’re munching on our crops, we tend to just let them do their incredibly slow thing.

Then there’s New Zealand’s Powelliphanta snail. The members of this nocturnal and carnivorous genus can grow to the size of a person’s closed fist and – as seen in this striking film by BBC Earth – they have a rather spectacular way of devouring their prey. Sneaking up on its unassuming earthworm dinner, it launches its elastic mouth towards it and draws it in with powerful, inescapable suction.

The earthworm tries to escape, but its attempts are for naught. In the dark and wet vegetation-covered landscape, the worm meets its end as all 6,000 of the snail’s teeth clamp down on it and chew it into oblivion.

The narrator of the incredible video notes that scientists are not sure precisely how the snails track down their prey.

 

Giant Snail versus Earthworm. BBC Earth

These hermaphroditic predators live for up to 20 years, and spend most of their time hunting down their prey on the forest floor. They are considerably rare, which is why it’s taken so long for footage of their dining habits to come about.

Their evolutionary history goes back at least 235 million years, where they originated on the supercontinent of Gondwana. When Australia segregated itself from New Zealand around 80 million years ago, they went along with the latter and have stayed there ever since.

They can come in all sorts of colors, from red to yellow to black – but back in 2011, a gold-shelled, white-bodied albino giant snail was spotted in Kahurangi National Park.

Their main predator is the weka, a flightless bird. However, since the arrival of the colonialists in the not-too-distant past, their numbers have reduced quite dramatically. Introduced mammalian predators, particularly rats and possums, have made a huge impact, and the extensive habitat repurposing by farmers and companies have significantly shrunk their geographical range.

New Zealand’s Department of Conservation (DoC) describes these giant snails as being “as representative of New Zealand’s unique evolutionary history as the kakapo, moa, or kiwi.” However, it adds that “despite being legally protected, New Zealand’s Powelliphanta land snails are under serious threat. Several species are in danger of extinction.”

In fact, the DoC has considered the plight of these massive snails to be serious enough to warrant some rather drastic mitigation measures.

In the last two decades, aerial poison dispersions on a truly massive scale have been conducted in order to cull the rising numbers of mammals. The data seems to show that it has worked to some degree, with snail numbers on the rise – but dumping poison from the sky is a somewhat imprecise and risk-prone method.

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