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Giant African and New Zealand Land Snails: Fascinating Mollusks

Linda Crampton is a writer and teacher with an honors degree in biology. She loves to study nature and write about living things.

A giant African land snail (Achatina fulica) in India

A giant African land snail (Achatina fulica) in India

Two Giant Snails

The giant African land snail and the New Zealand Powelliphanta are huge animals compared to common garden snails. They are fascinating mollusks to observe and study, but unfortunately one is a potential pest and the other is either threatened or endangered, depending on the species.

The shell of the giant African land snail species found in the United States may reach more than eight inches in length. The animal is a herbivore with a very large appetite and can be a serious agricultural pest. It may sometimes carry a parasite that causes meningitis in humans. The snail is long lived and can reach ten years of age. In some places, it's kept as a pet.

Powelliphanta is a genus of carnivorous snails. The genus name is also used as a common name. The largest species may be as big as a fist. Snails usually move slowly, but the lunge of a Powelliphanta for its earthworm prey is sudden and rapid. The animal may live for twenty years, an amazingly long time for a snail.

Powelliphanta augusta from Happy Valley in New Zealand

Powelliphanta augusta from Happy Valley in New Zealand

Snails belong to the phylum Mollusca and the class Gastropoda. The animals in the phylum are referred to as either mollusks or molluscs. The first term is preferred in North America while the second seems to be preferred in the rest of the world.

The Giant African Land Snail

Three species of mollusks from Africa may be called a giant African land snail: Achatina achatina, Lissachatina fulica (frequently known by its older scientific name of Achatina fulica), and Archachatina marginata. The species have a variety of common names, so it's often less confusing to refer to them by their scientific names. They belong to the same biological family, which is known as the Achatinidae.

The species most often found in the United States is Achatina fulica, which is sometimes called the giant African snail. It's native to East Africa but has been introduced to other areas of the world. Although the snail lives in a warm climate in its native country, it's a hardy animal. It survives cold weather and snow in the United States by hiding, slowing its metabolism and becoming sluggish, or hibernating until warm weather returns.

A Pet Giant African Land Snail

Giant African Land Snails are sometimes referred to as GALS. The term is used in both the singular and the plural.

Physical Appearance

The giant African snail generally has a conical shell that is reddish brown with yellow bands. The shape varies, however, and the color depends on the conditions in the animal's environment. The soft part of the body is usually brown or tan. An adult Achatina fulica sometimes reaches a length of eight inches without extending its body. It's not the biggest snail in its category that has been observed, however, as the quote below shows.

The animal has two pairs of retractable tentacles on its head. The upper, longer pair bear the eyes and are also sensitive to touch. The lower, shorter pair provide the sense of smell as well as touch. Like its smaller relatives, the snail moves by secreting mucus or slime and then moving over the slime with its muscular foot. The foot is the large, soft structure at the base of the animal.

The largest known land gastropod is the African giant snail Achatina achatina, the largest recorded specimen of which measured 39.3 cm (15.5 in) from snout to tail when fully extended, with a shell length of 27.3 cm (10.75 in).

— Guinness World Records

Diet

Achatina fulica has a voracious appetite and eats at least 500 different kinds of plants in its native habitat. It lives on the edge of forests and in agricultural areas and may become a major pest. It eats fruits and vegetables when it can find them—including garden and agricultural crops—but will also eat ornamental plants.

The snails are very invasive when they are outside their natural habitat. They destroy both crops and property. They even eat stucco from houses. The stucco contains the calcium that the animals need to make their shells.

Meal Time for a GALS

Reproduction

The giant African snail is a hermaphrodite, which means it contains both male and female reproductive organs. It also means that every snail can lay eggs if it obtains sperm from another animal. During mating, sperm exchange takes place between a pair of snails.

Each animal lays 100 to 400 eggs. The eggs are small, white, and round in shape. A snail can lay several egg clutches from one sperm exchange. The eggs are laid at two to three month intervals, which could result in at least 1200 eggs produced per animal each year. The young animals that hatch from the eggs are tiny, but they grow fast.

The videos in this article are shared for general interest. I've never had a GALS as a pet. I don't know whether the treatment of the pets in the videos is appropriate for keeping a snail healthy and comfortable. If you live in a place where keeping the snail as a pet is legal and you want to own one, you should explore how to care for it.

Introduction of Giant African Land Snails to the United States

Achatina fulica has been brought to the US both accidentally and deliberately. The snails may have arrived in cargo, hidden and unnoticed, but they have also been smuggled into the country. They are sold as pets and are reportedly kept in some schools, even though it's illegal to import or own a giant snail without a permit from the US Department of Agriculture.

In 1966, a boy living in Florida smuggled three snails into the country to keep as pets. His grandmother eventually set them free in the garden. After seven years, there were more than 18,000 giant African land snails in Florida, all resulting from this release. The eradication program required ten years and cost a million dollars. Unfortunately, as the video below shows, the animals have reappeared in Florida. They have the potential to be a very serious pest, attacking orchards and crops.

A Problematic Mollusk in Florida

According to information on the Florida Department of Agriculture and Consumer Services or FDACS website (referenced below), wild giant African land snails are still present in the state.

Possible Disease Transmission

There is a small chance that giant łand snails could transmit disease. The animals sometimes contain the larvae of a parasitic nematode known as the rat lungworm (Angiostrongylus cantonensis), though the CDC says that it's unknown if the GALS in the United Stated contain the parasite. The larvae can cause meningitis in humans. This disorder involves inflammation of the meninges, which are the membranes that cover the brain. The condition may not be serious, but it sometimes is.

The snails obtain the parasite by eating infected rat feces. If a snail was bred in captivity, is given clean food, and has never been outdoors, it's unlikely to have eaten rat feces. Animals collected from the wild might contain the parasite, however.

The disease is transmitted by other snails as well as GALS. If a snail contains the nematode, a person will probably need to eat the mollusk in a raw or undercooked form in order for the parasite to infect their body. I've seen no evidence supporting the idea that the parasite can be transmitted by slug slime. It's probably a good plan to wash the hands after handling a snail or a slug, though. People often decide to do this due to the slime deposit on the skin.

Unlike GALS, Powelliphanta snails generally aren't kept as pets. They are large snails when fully grown and have at least one interesting characteristic of their own. Their method of catching and eating earthworms is impressive.

A Powelliphanta Engulfs an Earthworm

They (Powelliphanta) suck up earthworms like spaghetti.

— New Zealand Department of Conservation

Powelliphanta Snails of New Zealand

Powelliphanta snails are also giants of the snail world and are found only in New Zealand. They are named after Arthur William Baden Powell (1901–1987). Powell was a malacologist (a scientist who studies mollusks) and worked at the Auckland Museum. He studied the snails and separated them from a related group in the classification scheme. The animals are classified in the family Rhytididae.

The largest species in the genus is Powelliphanta superba prouseorum. According to the New Zealand Government's Department of Conservation, or DOC, the animal can grow as big as a fist and has a shell up to 9 cm (3.5 inches) across.

The shells of Powelliphanta snails are flatter and rounder than those of giant African land snails. They are often a mixture of yellow, gold, dark red, brown, or black and are sometimes beautifully patterned.

The soft parts of the snail are typically black, dark brown, or grey in color. In November, 2011, an albino animal with a golden brown shell and a pure white body was found. Biologists estimated that it was about ten years old. They were surprised that it had avoided being killed by predators for so long, since its body showed up very clearly against its background.

Habitat and Diet

Powelliphanta snails live in moist lowland forests, high-altitude forests, or areas with alpine tussock, depending on the species. Tussock grasses grow in bunches, unlike the grass that we use for lawns. The species that live in alpine areas have to deal with very cold winters.

The snails are mainly nocturnal. They spend the day in a dark and moist environment, such as in crevices or under leaves or logs. During the night, the animals prey chiefly on earthworms on the forest or grassland floor. They also eat slugs and other invertebrates.

Shells of Powelliphanta hochstetteri bicolor

Shells of Powelliphanta hochstetteri bicolor

In snails, exchange of sperm and egg release occur through a pore on one side of the body near the head instead of from the rear end. This is due to a phenomenon known as torsion. During larval development, parts of the animal's body rotate 180 degrees with respect to the head and foot.

Powelliphanta Reproduction

Powelliphanta snails have a much lower reproductive rate than giant African land snails. They are hermaphrodites and exchange sperm with another snail. One animal may produce five to ten eggs in a year—far fewer than the potential 1200 or more produced by the giant African land snail.

The eggs are pink and have a hard shell that resembles that of a bird's egg. They are relatively large in size and sometimes reach 12 mm in length. Several months may pass before the eggs hatch.

A Huge New Zealand Mollusk

Endangered Animals

According to the DOC, at least 16 species and 57 subspecies of Powelliphanta snails exist. The survival of 40 species or subspecies is threatened by predation or habitat loss.

Predation

Possums are major predators of the snails. The possums were introduced to New Zealand and are now threatening many species of native wildlife. Rats, wild pigs, hedgehogs, thrushes, and weka (large, flightless birds) also eat the snails.

One problem for the snails is a phenomenon known as beech mast. The term refers to high levels of seed produced in beech forest. The seeds are eaten by snail predators, including rodents. An increased rodent population results, which in turn creates an increased threat to the snails.

Habitat Loss

Destruction of forest in the past has meant that Powelliphanta snails now live in limited areas. There are still conflicts over land use near or in the animal's habitat. Drainage of land and damage by livestock have been problems.

In some areas, open-cast coal mining is threatening the snail's existence. Powelliphanta augusta was discovered in a limited area after mining had been in progress for some time. Some snails were brought into captivity and others moved to new habitats. It's not yet known whether the latter transfers will save the species. It's adapted for success in the specialized habitat where the coal is mined.

A Powelliphanta Versus an Earthworm

A Possible Public Relations Problems

Powelliphanta snails are interesting creatures, but most people wouldn't describe them as being cute. That's part of their problem. People are often concerned about endangered animals that are furry, feathery, clever, or cute, but the fate of a snail doesn't worry them as much. In addition, the snails are usually active at night, when most people are unaware of them. Powelliphanta snails are unique animals. It would be very sad if they disappeared from the Earth.

The Future of the Snails

Although giant African land snails are interesting animals and are admired as pets by some people, they can be annoying pests. Their control is very important. It would be a shame if they disappeared completely, though, as long as they are living in a place where they aren't causing harm. Their history in the United States shows how problematic an introduced species can be.

Powelliphanta snails are less visible due to their nocturnal habits, but like GALS they are interesting animals. They are an important contributor to their ecosystem and nature's diversity. I hope that the species and subspecies that are in trouble survive.

References

© 2012 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on May 28, 2013:

Hi, peachpurple. Yes, snails are a type of mollusk. It must be annoying to have so many of them in your garden! Perhaps the snails die because they are being poisoned by something.

peachy from Home Sweet Home on May 28, 2013:

wonderful hub. So big snails are called mollusks. In my house drain, i could find dozens of mollusks with brown shells, unlike the photos you have shown. They love to eat off my garden plants and papayas. Funny thing is why do they die the next day? Thanks for the hub

Linda Crampton (author) from British Columbia, Canada on January 13, 2013:

Thanks for the votes, Peggy! In the warmer months we have lots of snails where I live, but they are small animals. I hope that the giant snails in Florida don't cause any problems to agricultural plants.

Peggy Woods from Houston, Texas on January 13, 2013:

We have lots of snails in Houston, Texas. I guess they thrive in our generally warm and humid climate. Amazing to know that some snails live for 10 or 20 years! I also did not realize that there were snails that got to be so large. Hopefully the Giant African Land Snails will be contained or eradicated in Florida so that they do not wreak havoc on the many crops or continue spreading across the U.S. Up and interesting votes!

Linda Crampton (author) from British Columbia, Canada on December 29, 2012:

Thanks for the visit leahlefler. Yes, I think that giant African snails are very interesting creatures, but I certainly wouldn't want them in my garden!

Leah Lefler from Western New York on December 29, 2012:

Giant snails - interesting! I have never seen one, though with the invasive species entering the US, it sounds like we might be close neighbors with them soon. My poor hostas would never survive an attack of giant snails!

Linda Crampton (author) from British Columbia, Canada on December 29, 2012:

Thank you very much for the comment and the vote, Nell. I'm glad to hear that someone else likes snails!

Nell Rose from England on December 29, 2012:

Fascinating look at this amazing snails, I remember a woman round the corner from my house had two of them, they were so interesting to look at and they actually didn't give me the ugg factor! lol! their little antennas on their head were swivelling around every time we spoke, fascinating stuff! another great animal info hub, voted up! nell

Linda Crampton (author) from British Columbia, Canada on December 28, 2012:

Thank you so much for the lovely comment, Deb! I appreciate your visit.

Deb Hirt from Stillwater, OK on December 28, 2012:

Fascinating! You come up with some of the best stories on animals. Rock on, Alicia!

Linda Crampton (author) from British Columbia, Canada on December 28, 2012:

Thank you very much for the comment and the votes, Kathi. I agree - these snails are amazing!

Kathi from Saugatuck Michigan on December 28, 2012:

Well, I became interested in mollusks cause of their prehistoric origins and also cause they are a problem in my garden. I'm glad I don't have the giant African species. They truly are amazing and the videos added much to this presentation! Voted up, useful and interesting! :O)

Linda Crampton (author) from British Columbia, Canada on December 28, 2012:

Thanks for the comment, Om. I think that many people would freak out at the sight of the largest giant land snails! They are impressive animals.

Om Paramapoonya on December 28, 2012:

Very interesting info. I've surely learned a lot from this hub! As I was reading this, I tried to imagine a giant snail that's about 8" long and 4" wide. I think I might freak out if I came across such a huge snail in my backyard!

Linda Crampton (author) from British Columbia, Canada on December 28, 2012:

Thanks for the visit, drbj. I guess I'm in the minority, but I do think that snails are cute, although not in the same way that my dogs, cats and birds are! It does take a while to get used to their slime, though.

drbj and sherry from south Florida on December 28, 2012:

Snails and slugs may be interesting to read about, Alicia, but I definitely do not want them as members of my household. As you point out, they are neither cute, furry nor any other adorable adjective. Promise.

Linda Crampton (author) from British Columbia, Canada on December 27, 2012:

Thanks for the comment and the vote, moonlake. It is unfortunate that some snails can damage our plants. They are interesting animals, but they can be a nuisance.

moonlake from America on December 27, 2012:

Interesting hub I have never heard of these big snails. I also like snails but I know what damage they can do. Voted up.

Linda Crampton (author) from British Columbia, Canada on December 27, 2012:

Thank you very much for the comment, Martin!

Martin Kloess from San Francisco on December 27, 2012:

Thank you for this truly fascinating hub.

Linda Crampton (author) from British Columbia, Canada on December 27, 2012:

Hi, Bill. I know that some people aren't attracted by snails (to put it mildly!) but I think that snails and slugs are very interesting animals. Thanks for the comment!

Bill Holland from Olympia, WA on December 27, 2012:

Yuck! I'm imagining stepping on one of these with bare feet. LOL Interesting facts, Alicia, but I hope I don't run into one of these. :)

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