Big Snails Mean Bigger Problems for Florida

The boys are back in town. Except, technically, they’re not “boys,” but hermaphroditic land snails. Also, the “town” in question is three separate counties in central and southern Florida. Let’s try this again: Giant African land snails, a potentially devastating invasive species, have re-appeared in three Florida counties.

In Broward County, just north of Miami, one of the gargantuan gastropods was found earlier this month. To try to halt the spread of the mollusks, state officials announced a ~5 square mile quarantine zone in Broward on Monday. Under the quarantine, transporting snails, soil, plants, compost, or building material is now outlawed—except with specific approval from the Florida Department of Agriculture and Consumer Services (FDACS).

The newly established quarantine area joins two others previously designated across the state: One in Lee County and another in Pasco County. In each of these three zones, Florida officials are working to eradicate, not just corral, the snails. The state agriculture department is using the toxic pesticide metaldehyde—which messes with snails’ slime production—to try to kill the burgeoning populations before they can kill everything else.

You see, giant African land snails are voracious eaters known to consume more than 500 types of plants including important crops like beans, peas, cucumbers, and melons. If their preferred food sources aren’t available, the snails will default to munching on just about anything else they can get their maws on, including ornamental plants, native vegetation, tree bark—even the paint and stucco on buildings, according to the U.S. Department of Agriculture. The fist-sized mollusks are native to East Africa. But in Florida, they pose a big threat to the state’s farm industry and natural environment.

As a bonus, the gooey gastropods often leave more than slime trails in their wake. They carry a parasite, called rat lungworm, known to cause meningitis in humans. If a person eats a snail infected with rat lungworm, or unwashed vegetables contaminated with an infected snail’s slime, they can end up sick. Though many species of slug and snail are capable of transmitting the parasite, giant African land snails can be particularly problematic because of how quickly they can breed, their lack of natural predators in Florida, and their penchant for crop plants. They’re “one of the most invasive pests on the planet,” by FDACS’s description.

Just a single snail (no mate needed, thanks to the species’ specific biology) is capable of laying thousands of eggs in a year. They can spread miles at a time by hitching rides on vehicles or in transported yard waste. When conditions aren’t ideal for snail shenanigans, they can enter stasis, buried in the ground for up to a year until circumstances improve. In short: getting rid of them is a challenge, yet it’s one Florida has tackled before.

The state has previously dealt with giant African land snails on two occasions. The species was first introduced to Florida in 1966 in downtown Miami. Through a $1 million program (~$3 million in 2021 money) to destroy the animals and their eggs, the pests were declared eradicated by 1975. But then, in September 2011, the snail was re-introduced. It took another decade, and more than $23 million this time around, to clear the state of the snails, according to the USDA. In 2021, the species was once again eradicated.

The giant snail population detected in Pasco County in 2022 is genetically unrelated to the snails eradicated from Miami-Dade County the year prior, the federal agency says. Broward and Lee counties’ snails could be genetically distinct too. Although it’s not exactly known where these recently detected gastropods first came from, there are a few possibilities. The USDA suggests the snails might be pet releases— keeping giant African land snails as terrarium pets is illegal, but people still do.

The animals may have also been purposely brought over to be eaten. They’re considered a prized food in West Africa and have been seized by U.S. Customs and Border Protection before. Recently, officials intercepted six live snails in a suitcase at the Detroit airport. Alternately, like many invasive species, Florida’s newly detected pests may have made their way to the state through eggs accidentally carried on imported plant matter. The animals are widely introduced around the world and are found throughout China, India, Southeast Asia, and parts of South America. Or, perhaps, Florida’s past eradication attempts haven’t been quite as successful as they were assumed to be.

If you are a Florida resident and think you’ve spotted one of the giant invaders, snap a picture and contact FDACS’ Division of Plant Industry. You can call the helpline at 1-888-397-1517, or send an email to DPIHelpline@fdacs.gov.

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