Return of the cannibal snail good for garden
People need to reintroduce cannibals into the garden.
This is the common name for the indigenous Natalina cafra amathole or Natalinas, a carnivore snail which feasts on the reviled invader and plantchomper, the common European snail cornu aspersum.
The Natalina cafra eumacta is an even more efficient local predator of the European invader, says East London museum malacologist (mollusc scientist) Dr Mary Cole.
“It’s shell gets up to 5.5cm across. They are strictly carnivorous, eating smaller species of snails.”
Snails are an excellent indicator species of anthropogenic damage to the environment, but in a counterintuitive sense they are such hardy, discreet survivors.
If they were not found, then something was seriously wrong with the environment, she said.
Snails are largely forest creatures, and with the decline of dune and scarp (river valley) forests, are being forced into smaller spaces.
When forest is trampled by humans or cattle, or reduced or cut down, the snails die off.
Snails still need “an intact natural habitat” to survive.
It is getting so bad, that Cole has at least 16 indigenous snail species that she is preparing to get accepted onto the red list of species threatened with extinction.
She said land snails had suffered the most extinctions among molluscs, and this had been happening since the 1500s, when agriculture and land clearing started to get going.
Very few of SA’S 247 snail species — 97 of them only found in the Eastern Cape — were listed in SA simply because no-one had taken the trouble to research them, and this was about to change, the IUCN Red List-accredited scientist said.
One snail definitely going on the list will be the carnivorous little hunter snail, pulella aprosdoketas, which is under threat in forested areas of former Transkei.
In places such as Papua New Guinea some “gorgeous” tree snails had gone extinct through over-collection.
Molluscs were the secondlargest species on Earth after insects, and included local species of mussel, limpets and oysters.
Cole’s research in 2000 found that there was a decline of mussels and oysters due to overcollection at Bonza Bay and Chintsa, which left open places to become quickly overgrown by seaweed, making it difficult for molluscs to resettle.
She said more SA snails would be added to the list in future because they were threated by land drying out, dwindling forests and other habit encroachments.
Cole said she was working especially hard to get local snails red-listed and protected by law because she was worried about the way open spaces were being eliminated in BCM.
“People clear everything, every blade, and pave it. The perception is that open spaces are a liability.
“I worry about blue duiker, which are on the red list. It used to be common in dune forests here but I hardly ever see them.
“They are being poached, while people whose dogs are not on leads are creating a disturbance, causing buck to flee.
“There is a general lack of thinking about anything other than themselves,” she said of illdisciplined dog owners.
There were also only a few grey (common) duiker and bushbuck left in BCM reserves.
People who wanted chameleons to return needed to recreate their habitat, which included thorn trees.
“Cats are a huge problem. I like them but people don’t care if they catch a lot of lizards and chameleons, or anything.
“It can be fledgling birds which flutter to the ground for a few days and are easy targets.”