Introduced Species Summary Project
Giant (East) African Snail (Achatina fulica)
Figure 1 – Achatina fulica Thailand
Common Name: Giant (East) African Snail (giant African land snail, escargot Geant, Achatine, Caramujo)
Scientific Name: Achatina fulica
Phylum or Division: Mollusca
Order: Pulmonata Suborder: Sigmurethra Infraorder: Holopodopes
Identification: Full grown Achatina fulica reach up to 20 cm in length and 12 cm in maximum diameter. The dark and light brown (sometimes more of a cream color) swirls wrap around its cone like shell. Its convex body allows for about 7 to 9 whorls. The outlines of the whorls fluctuate from narrow to broad even within the same colony. An adult Achatina Fulica’s lip opening is generally very thin and sharp. The shell itself is thick and strong if healthy (needs a high calcium diet). The rest of the body resembles a slug like appearance with a variance in color.
Figure 2 – Anatomy of an achatinid snail
Current Distribution: Giant African Snails can be found in
most southern hemisphere countries, eg. throughout
Site and Date of Introduction: As indicated in the map below,
introduction of Giant African Snails dates back to the early 1800’s. These snails spread throughout
The first occurrence of
these snails outside of
Giant African Snails
were first spotted in the
In 1958, a young boy
stashed Giant African Snails into his suitcase from his travels in
These snails continue to
In the early
2000’s the introduction of Giant African Snails have also occurred in
Figure 3 - Dissemination of achatinid snails from
Introduction: As mentioned above, Giant African Snails are
intercepted most often in the
If these snails are not immediately intercepted, they populate exponentially making it extremely difficult to control in a timely and cost efficient fashion.
Reason(s) Why it has Become Established: Achatina fulica begin laying eggs at 5 to 6 months. Each snail can produce from 10 to more than 400 eggs, 8 to 20 days after mating. If optimal conditions exist, a single snail can produce from 300 to 1000 eggs in 3 to 4 batches per year. In tropical (humid) conditions, eggs can hatch after 11 days. Giant African Snails’ lifespan lasts about 3 to 5 years, however some may live as long as 9 years.
Even though Achatina fulica prefer and thrive in more humid and warm conditions, they are highly adaptable to dry and cooler climates. They hibernate 10 to 15 cm deep in soft soil during less favorable conditions for up to one year. Their herbivore diet includes over 500 different plant species, including breadfruit, cocoa, papaya, peanut, rubber, and most types of beans, peas, cucumbers and melons. In addition, they forage on animal matter, lichens, algae and fungi.
The Achatina fulica produces a heavy slimy substance allowing for smooth and easy travel across rough and sharp surfaces. They can slide over a razor blade without being injured.
Ecological Role: Achatina fulica forage on over 500 different plant species. During less favorable conditions (dry, cool), they nest in lose soil for during their period of hibernation. One may postulate that this behavior promotes health in the soil as the soil is churned and as matter from the snail settles into the soil. However, with over population, the snails destroy and pollute their surroundings, including the soil.
Benefit(s): Giant African Snails contribute to
the degradation of animal matter. In
addition, the Giant African Snail provides nutrients to the
The hermit crab is one of the most dangerous predators to the Achatina fulica and has been known to use the shell as its home. The coconut crab also views the Achatina fulica as a delicacy. The domesticated duck along with a vast variety of other bird species forage on Giant African Snails. Other mammals such as the wild pig prey on Achatina fulica.
Threat(s): The Giant African Snails’ greatest lethal threat to humans is eosinophilic meningitis. This condition is caused by the rat lungworm parasite, angiostrongylus cantonesnsis. Most often this parasite is transferred by eating the snail, as some humans consider snails a delicacy. In addition the Giant African Snail can carry the gram-negative bacterium, aeromonas hydrophila, causing a wide variety of symptoms, especially in persons with a weak immune system.
Giant African Snails cause great economic peril to farmers due to their propensity in consuming large amounts of crops/plants. Their diet consists of over 500 different plant species. A wide variety of horticulture and medicinal plants are known to be attacked by this snail. Not only does this decrease the income for agricultural producers, but it also impacts their living conditions (often requiring relocation) and decreases food and medical resources for humans, animals and other species.
The economic consequences persist in eradicating these creatures, sometimes costing millions of dollars. Another economic penalty involves the decrease in tourism. As noted earlier, Giant African Snails thrive in warm, tropical conditions – often tourist destinations.
Figure 4 – Giant African Snail invading plant site
The most significant time period for the Giant African Snail to cause destruction to a given area is when it is first established. Their ability to reproduce exponentially with in their first 5 to 6 month of life offers little time to respond to such infestation. Therefore, the Giant African Snail is designated as “high priority” for the need to be controlled/eradicated immediately after the first sighting in a given area.
Control Method: Molluscicides have been designated as one of the most effective means to eradicate the Giant African Snail. The most widely used active ingredient is the metaldehyde. The downside is that most molluscicides negatively impact the soil, plants and other beneficial organisms (such as ground beetles and earthworms).
Iron phosphate is becoming more popular in use for killing snails with less negative consequences to other beneficial organisms.
Education provides great opportunity to decrease and eventually stop the illegal trading and importation of the Achatina fulica. Educational institutions would prohibit such introductions of this snail if the lethal consequences were known. The same would be true for pet trade stores selling these creatures as pets.
The above measures are the most effective in controlling across large
areas of land. Other methods, such as
creating frigid temperatures or saturating the snails in ethanol, are also
effective in controlling the Giant African Snail.
The Animal and Plant Health Inspection Service: http://www.aphis.usda.gov/ppq/ep/emerging_pests/gas.html ; http://www.aphis.usda.gov/ppq/ep/emerging_pests/pdf_files/achatinafulica.pdf
The Giant African Snail: A problem in Economic Malacology. Chapter 7. Biological Control. : http://www.hear.org/books/tgas1961/pdfs/tgas1961chapter07.pdf
United States Department of Agriculture: National Agricultural Library: http://www.invasivespeciesinfo.gov/animals/africansnail.shtml
Figure 1: Achatina fulica
Figure 2: New
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