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Giant Snail Invasion

Giant Snail Invasion Giant Africa land snail
Photo Credit: J.M.Garg [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0], via Wikimedia Commons

Giant East African land snails are wreaking havoc in South Florida.


Transcript

Aliens invade Florida. I’m Bob Hirshon and this is Science Update.

Giant East African land snails, up to eight inches long, have become a major pest in South Florida. According to entomologist Trevor Smith of the Florida Department of Agriculture, the snails eat virtually all kinds of plants, and also voraciously seek out calcium for their shells.

Smith:
So if they can’t find limestone or maybe a cement block or something on the ground, they’ll just climb up on the wall of the house and start eating the stucco. So not only are they a plant pest, but they can actually eat your house.

It’s not clear how the snails got here, but in just nineteen months since the first sighting, their population has exploded. Thanks to a massive public information campaign, regular citizens have identified many infestations. Authorities then hand-collect the snails and leave baits laced with iron, which kills the stragglers. I’m Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

These giant snails are one of many examples of invasive species. That's a term for a plant, animal, or fungus that gets transported from one ecosystem to another, sometimes on the other side of the globe. Since invasive species often have no predators or natural competitors in the new environment, they can multiply quickly, crowd out or devour native species, and cause widespread ecological damage.

Many invasive species, in and of themselves, aren't easily noticed by humans. In many cases, the public isn't aware of their effects until they directly or indirectly start destroying crops or killing native plants and animals. Even then, the alien creatures themselves may be hidden from view, or hard to distinguish from native species.

A few, however, can't help calling attention to themselves. These include a razor-toothed predatory fish called the snakehead, that can live on land for days, which was recently spotted in New York City's Central Park, and Burmese pythons, which have invaded Florida's Everglades and are eating endangered species and even pets. These rat-sized snails are also big enough to attract attention—especially when they chew on the walls of houses.

Nobody knows exactly how the snails arrived. There are several possibilities. They may have been imported as exotic pets, and then released into the wild when the owners grew tired of them. They may have stowed away from distant destinations on shipping containers, or crawled into the luggage of someone taking a vacation or business trip. When the snails are young and small, they can do so without anyone noticing—or even if they did, they might think it's an ordinary snail, and just set it free in the yard.

Aside from being voracious eaters, the snails multiply at an incredible rate. According to the researchers, one snail typically lays 1200 eggs a year, but in captivity, they've been known to double or even triple that number. What's more, the eggs can remain dormant underground, and time their hatching to when the soils are wet enough to indicate good foraging conditions above. In East Africa, where the snails come from, local predators and competitors keep their populations in check. But in South Florida, they have no natural enemies, so the snails chew their way through plants and homes with reckless abandon.

The only way to get rid of the snails, unfortunately, is by painstakingly collecting them by hand. The state of Florida has created a massive public awareness campaign, putting information about the snails on TV, radio, the Internet, in the mail, and on billboards and public ads. It seems to be working, since many of the invasive populations have been first spotted by civilians. 

Once authorities confirm the presence of snails on a property, they pick up every snail they can find, and leave behind baits that will poison others left behind. Fortunately, the snails have a simple weakness: iron, which is common, cheap, and harmless to many other species. The baits are also designed to attract snails and not other animals. It's hard work, but the state actually beat back a smaller invasion of the same snails in the 1960s, using similar techniques. Hopefully, the snails will lose this round as well.

Now try and answer these questions:

  1. What is an invasive species?
  2. As an invasive species, what advantages do the giant snails have in Florida that they don't have in their native East Africa?
  3. Why is a public information campaign crucial to eradicating the snails?
  4. Would you expect that invasive species are a bigger problem today than they were 200 years ago? Do you expect they will become a bigger problem in the future? Why?
You may want to check out the April 19, 2013, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: Giant aliens attack Florida, unsticking geckos, the worlds within carnivorous plants, and mapless migrant monarchs.
 

Another hungry invasive species plaguing Florida is the Burmese python. Find out more in the Science Update Everglades Pythons.

Learn how invasive species can use trash to travel around the world in the Science Update Litter Life.

In the 2012 BioBlitz BobCast 2: Controlling Invasive Plants, reporter Bob Hirshon interviews biologist and invasive plant fighter Jamie Evans of Rocky Mountain National Park.


Going Further


For Educators

Another hungry invasive species plaguing Florida is the Burmese python. Find out more in the Science Update Everglades Pythons.

Learn how invasive species can use trash to travel around the world in the Science Update Litter Life.

In the 2012 BioBlitz BobCast 2: Controlling Invasive Plants, reporter Bob Hirshon interviews biologist and invasive plant fighter Jamie Evans of Rocky Mountain National Park.


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