Bermuda land snail thriving on Nonsuch Island
“Lazarus” snails, thought extinct for years before being discovered found clinging to life in isolated areas, are thriving after being reintroduced to Nonsuch Island.
Research shows the greater Bermuda land snail is now reproducing and expanding beyond the areas where it was originally released on the isolated island in Castle Harbour, according to the Envirotalk newsletter.
Plans are under way to reintroduce the snail on at least ten islands across Bermuda in early 2020, and ecologists hope to build self-sustaining populations of several thousand mature snails.
Mark Outerbridge, a wildlife ecologist for the Department of Environment and Natural Resources, wrote in Envirotalk: “Thanks to the care and dedicated efforts of so many different people, Bermuda’s Poecilozonites snails are still among the land of the living.
“The greater and lesser Bermuda land snails are all that are left of a once mighty clan that has had a very long and fascinating history. The loss of these snails would not only mean that their respective species would go extinct but the planet would actually lose an entire genus.”
Fossil records show greater and lesser Bermuda land snails were among a dozen of the genus, pronounced “pee-cil-o-zon-eye-tees”, of snail to once call the island home.
Scientists believe the genus could have propagated from just one animal to survive a trip across the Gulf Stream from Florida in antiquity.
By the time of Spanish arrival, the fossil record shows it had “radiated” into multiple species of varying sizes.
The introduction of predatory animals from the Old World and pesticides in modern times, meant none were seen from the late 1960s to 1970s.
In the 1920s, the Otala, or milk snail, was accidentally introduced and in the 1950s, using the wisdom of the time, cannibal snails, particularly Euglandia were brought here to control it. But the Bermuda land snail suffered particularly badly because it had no natural aversion to the cannibal snails.
In the summer of 2000, a summer student, Alex Lines was sent out by Conservation Services to find survivors.
Several clusters were found. In 2014, Alex’s father, Bruce, found a cluster of the species in the back courtyard, in Hamilton.
Dr Outerbridge said: “It just so happened that a small, but thriving, colony was inhabiting a narrow, dank alley behind Bruce’s shop.
“The concrete jungle of Hamilton had kept the snails isolated from their main predators and allowed them to find a way to survive.”
Dr Outerbridge said a second subpopulation of greater Bermuda land snails was later found on Port’s Island by Miguel Mejias, another summer intern, in 2017.
Snails were taken to Chester Zoo in Britain, where a successful breeding programme resulted in 18,000 snails being brought back to Bermuda and placed on five Castle islands including Nonsuch.
Dr Outerbridge said: “These islands had suitable environments to support the snails and appeared to be free of the major predators.
“The relatively large size of the greater Bermuda land snail, in comparison to the lesser Bermuda land snail, meant that the research team was able to apply tags to the shells of adults and study their survival in the wild after being released.”
He said a follow-up study found the snails quickly embraced their new island homes.
Dr Outerbridge said: “One study has already shown that the snails don’t seem to be too picky in choosing the leaf litter they live in, except for areas dominated by casuarina trees; they had significantly fewer snails than did places growing mixed deciduous trees.
“Rocky limestone outcroppings were particularly popular with the snails, presumably because they are good places to retreat into and under when the weather gets too hot and dry.”
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