The Giant Snails

A giant African snail has broken loose from its native habitat and is now on the rampage. It has devastated parts of Hawaii and the Orient and within recent months has made its stealthy appearance in California, having been brought bach on salvaged war material. ALBERT R. MEADof the Zoology Department of the University of Arizona began investigating the giant snail in British West Africa in 1944: he is leading the campaign for state and Federal quarantine laws with which to protect oar crops from this ruthless invader.



WHO said snails are slow? About one hundred years ago, a giant African land snail began heading for the far corners of the earth. Wherever it traveled, destruction went with it. During the war in the Pacific it accelerated its speed in jumps that have landed it right here in the United States. Millions upon millions of dollars of damage has been left in its path. Lush tropical vegetable gardens have been stripped of their leaves and flowers, and even the more tender pieces of bark. Our gardens and crops are next on the menu unless the invader can be stopped.

The giant African snails are six inches long and as big around as an orange. They have the unromantic name of ACHATINA fulica but their appearance is attractive; every shell presents a little different combination of soft greens, purples, pinks, and browns with frequently interspersed snow white. They have no difficulty in feeding themselves; they will eat almost anything (and everything) you happen to have in your garden, and they stay around until all the food is gone. They live for several years, and when it conies to multiplying they make the proverbial rabbit look like a piker.

The trouble is that these snails are now on their wag to your gardenen masse.

As far as we know, they staked out their original land claim all along the east coast of Africa from Natal and Mozambique in the south to Kenya and Italian Somaliland in the north. But apparently because they have not much of a hankering for altitude, they were stopped in their northern incursion by the mountainous country of Ethiopia.

In this wide African playground they were neither abundant nor rare. Like most animals in natural conditions, they had reached an equilibrium with other members of their environment. The African natives, who say they are good to eat, have known of these, snails since earliest times and have made good use of both their shells and their carcasses. Highly prized as human food, they are usually dropped alive into boiling water, removed from the shell, cleaned, chopped, and included in all sorts of native food concoctions — from soup to a thick starchy, oily mush.

The larger shells are used as containers for salt, oil, or sauces, and as drinking cups. Sometimes they are cut into strips and made into spoon-like utensils. In some African tribes the wayward child who persists in wandering away has a noisy string of smaller shells tied around his wrist, waist, or ankle — à la cow. In other tribes the wearing of these shells is believed to endow the owner with especial immunity to certain types of evil forces (whatever they are).

In many parts of Africa, including much of the West Coast, liny sequin-like disks are cut out of the shells by fond grandmothers. These are strung by the thousands to form I mm one to several strands around the hips of the younger women. In parts of the Gold Coast and Nigeria, I often saw these worn as the sole item of apparel.

The earliest reliable records of Achatina fulica place it on Mauritius — a tiny island between Madagascar and India. So far as we know, the snail’s first big move did not occur until 1847. In that year a British collector and traveler, W. H. Benson, visited his good friend Sir David Barclay, also an amateur collector, on Mauritius. There he saw Achatina fulica crawling all over Sir David’s gardens.

Benson decided to take some of these snails with him to India, and in April he let them loose in the Chouringhie Gardens, near Calcutta. A few months later, after his return to England, he learned that they were multiplying and spreading to a great extent. He also learned that the Indians were not taking to them at all as a possible delicacy.

The snail’s next stop was the island of Ceylon, where it was introduced about 1900. It was there that its potentialities as an agricultural pest were first convincingly demonstrated. To add insult to injury, the lack of lime in the soil prompted these snails to rasp off-, with their file-like tongues, the lime from the native houses!

By 1911 the snails had readied Singapore, Malaya, and by 1928 they had spread south to Sarawak, Borneo, where in three years they became such a pest that a bounty was placed on both the snails and their eggs. Within two weeks, approximately half a million snails and twenty million eggs were collected and destroyed. But a few weeks later the snails were as numerous as before. Still further south, in Sumatra and Java, the snail made its presence known in 1988, when its appetite for young rubber plants gave it an even blacker name.

Front Singapore it spread north to Amoy, China, in 1931 and across the straits to the Japanesecontrolled Formosa two years later. Probably sometime in 1937 it was introduced into Hong Kong, and by 1941 its population numbered “untold millions.”In 1947, over five tons of snails were collected in just four small localities in that region, but with no appreciable effect upon their rapid spread.

The Japanese people of Formosa welcomed these snails not only as an exotic item of food but as a new medicine of supposed unusual qualities. This fact undoubtedly explains the frequent introduction of the snail into the Japanese mainland since 1986. The severe winters there, however, may have helped to prevent its rapid establishment.

A Hawaiian on the island of Maui received through the mails in November, 1936, eight specimens of Achatina fulica sent by his Japanese relatives. The Japanese had found them a self-perpetuating delicacy and a medicine. Why not send them to Hawaii? There was no law against it.

The recipient hoped to raise them and sell them at a good price in Hawaii. And this lie did for a year and a half, until one of his buyers unwittingly exposed the whole mess. The specimens were brought to the late Dr. C. Montague Cooke, Jr., the eminent malacologist or snail specialist of the Bernice P. Bishop Museum, who immediately identified them as the dread giant African snail.

Things moved fast after that. The agricultural authorities destroyed these samples and went hotfoot to the snail raiser on Maui. They found that his original eight specimens had already produced nearly 1500 large snails and countless smaller ones, to say nothing of the 425 that the grower confessed having consumed himself! Efforts were quickly made to destroy every specimen.

But there were complicating factors. A Hawaiian woman visiting in Formosa, in that same fateful year of 1936, out of sheer female curiosity decided to take a couple of these giant snails back home to her garden in Honolulu. She carried them in her grip and did not declare them. And the anxious authorities in their search for other possible populations of these snails really hit the jackpot on Oahu. They soon realized that the snail population of this island had gotten completely out of control.

On Maui, in the meantime, the snails had broken out anew with the uncontrollability of a forest fire whipped by a dry south wind. School children were enlisted to gather the snails and eggs and spot new populations. The authorities tried covering all the vegetation in the infested and adjacent areas with the very poisonous sodium arsenite spray; they tried baits containing met aldehyde; they tried appealing to the snail’s appetite for lime by painting rocks, fence posts, tree trunks, and the like with a mixture of cement, calcium arsenite, and lime.

These methods and others were used in every conceivable combination for ten years at a cost of $120,000. But at this very moment the snails are still abundant and greatly increasing in numbers. Dr. C. E. Pemberton of the Hawaiian Sugar Planters’ Association recently said, “We have finally realized that eradication is impossible without the expenditure of vastly more money than the Territory can afford. The only thing that has effected any measure of control has been the judicious, speedy enactment of laws making it punishable to possess or transport these snails. They have thus been successfully restricted to the two islands of Maui and Oahu.

The worst invasion of all was organized by the Japanese in the early phases of the war in the Pacific. The Japanese people had been familiar with Achatina fulica for several years and it was only natural that they should take it with them into captured territory. For the Japs it was a good source of “ wild food" to supplement the scheduled rations or take their place in the event that supply lines were cut. The carting of this snail through the Pacific islands has already had more lasting destructive effect than the most severe scorchedearth policy. Through either the direct or the indirect efforts of the Japanese, billions of these snails are now found in the Dutch East Indies — especially New Britain, New Ireland, and New Guinea; in the Philippines; in the Bonin Islands; and in the Micronesian islands of Saipan, Tinian, Guam, Pagan, and the Palau Islands of the Caroline group.


NO ONE can possibly imagine the destructive abundance of these giant snails until he has seen them. In the daytime they hang not just all over the coconut tree trunks, but one on top of the other after “standing room only “has gone. As you walk in the shade of the dense jungle growth, you crunch the young snails that litter the forest floor under your feet as though you were walking on bird’s eggs. Small bushes hang thick with the diurnally resting snails. These roll to the ground like ripe fruit when the bushes are shaken. The early evening presents a more startling effect, for the flashlight reveals the snails in countless hoards actively crawling, in search for food, over every tree, rock, hoard, house, or other item upon which the light happens to fall. With this picture in mind, is there any wonder that there have been desperate cries for help coming in from the Pacific?

Why have these snails multiplied into such untold billions in so short a time? They have lived in East Africa for countless years and are living there now without all this display of fecundity. First of all, these snails have invaded their new territories in the absence of their natural enemies. What are these natural enemies? Certain lizards, beetles, ants, small carnivores, rodents, and birds occasionally will attack, kill, and consume the smaller snails and more rarely a larger individual. But it is man himself who is the greatest natural enemy of these giant snails.

Man, in the case of the Africans, the Japanese, and some Chinese, has the appetite for them; he also has the facilities for destroying them. The larger snails are protected by a heavy, china-like shell I and a thick tenacious slime which is poured out all over the exposed parts of the body when the snail is irritated. These devices successfully ward off attacks from less adept aggressors. Many of the introductions in Asia were made with the intent of using the snails as poultry feed. But because the larger ones could escape the attacks, sufficient young snails have been produced to keep both the poultry fed and the snail population on the rampage.

When the young individual hatches out of its egg shell, it is recognizably a small snail with a thin, roundly pyramidal shell about as big as a pea. Before it is a year old, it becomes sexually mature, in every case, as a male. A few months later, in every case, the female tract becomes fully developed. Each individual then is a true hermaphrodite with but a single gland that produces, at the same time, both male and female sex cells.

The eggs are about the size and shape of blackeyed peas and have a very hard, smooth, canaryyellow shell. Any little depression in the soil under a rock, a board, leaves, or the like, forms an inviting repository for the eggs. Some of the individuals will retain the eggs in the uterus so long that they take only a few hours to hatch. And in some related species they are habitually retained still longer, so that they actually hatch within the uterus. The young are then brought forth alive or “ovoviviparously” as the technically inclined prefer to express it. The protective nature of this retention within the uterus of the nearly invulnerable adult is obvious.

It is the newly hatched snail that is most vulnerable to attacks from its enemies. But with up to three hundred eggs laid in a single batch, these snails can well withstand a high mortality rate in the young. The most startling element in this whole hermaphroditic setup, though, is the fact that every individual is an egg producer. In fact, one scientist mathematically figured, most conservatively in every way, that in five years a single gravid individual could give rise to a possible population of nearly eleven billion snails. Their aggregate weight would amount to almost as many pounds.

There are still other factors that amply explain the great survival rate these snails enjoy. For one thing, they are not finicky about what they eat, and rival the barnyard pig in their gustatory versatility. Among the more common food items are rotting fruits and vegetation, young shoots, tender pieces of bark, humus, excrement of humans and live stock, and even stepped-on individuals of their own species for a bit of passive cannibalism.

One food item that Achatina fulica is absolutely dependent upon, however, is lime. It is the lack of this in the soils of West Java and Ceylon that has forced snails there to rasp off the lime from the native houses. In contrast, the coralline islands of the South Pacific have an abundance of lime, thus automatically eliminating one more factor that might otherwise limit numbers.

The snails usually feed at times when they are least apt to encounter the attentions of their enemies: at dusk, at night, in the early morning, and during the day when it is raining. At other times they secrete themselves as much as possible. If circumstances force them to remain conspicuously out in the open, they seal themselves off and cement themselves tightly to some object with the aid of a limy albuminous secretion around the aperture of the shell. This successfully keeps out any nosy would-be predators or parasites.

During a food shortage or a dry spell, they bury themselves deep in the ground and make a similar secretion over the entire aperture of the shell save for a slit permitting air to be occasionally taken into the single large lung. I kept one in this quiescent condition in the Gold Coast for nearly six months. Sprinkling the specimen with a little water persuaded it to come out and look around for food. There were no outward signs that it had undergone the rigors of such a prolonged period of suspended animation. Its huge liver had held enough stored energy to permit, the snail to survive this long period of fasting. This ability to withstand adverse conditions of food and moisture helps further to explain why these snails have been carried such groat distances with often considerable time consumed in transit.


I THINK we can now appreciate why the U.S. Navy was frantic when it took over the problem of trying to set things straight in some of the infested islands of the Pacific Trust Territory. In fact, the Navy’s plight was so desperate that it sent in an SOS to the National Research Council with the request that something be done about these ever increasing snails. In accordance with the advice of Harvard’s Dr. Joseph C. Bequaert, the foremost world authority on these snails, I was asked to return to Africa to attempt to find specific parasites as the first step in a proposed plan to control the snails biologically. I could not leave my present position, however, and Dr. F. X. Williams, an entomologist of the Hawaiian Sugar Planters’ Association, went instead, to Mombasa, Kenya, and the island of Zanzibar last year.

The second step was to find ways of breeding any parasites that might be found, so that they could be introduced in great numbers in the infested areas, the theory and hope being that the parasites would soon make short work of the snails.

From my study of closely related species of giant snails in the Gold Coast, I had previously predicted that it was extremely unlikely that a suitable parasite would be found.

After six months search in the jungles, Dr. Williams substantiated my prediction. The search was not in vain, however, for a predator in the form of a while carnivorous snail, of the genus Gonaxis, about the size of a chocolate cream, was found to have real promise as a controller of Achatina fulica.

It must not be forgotten, however, that this fellow has not done a very good job at home. Nonetheless, specimens were shipped to Hawaii for further study and they have proved themselves able to rasp away the flesh not only of Achatina fulica but of almost any other snail that is put in the cage with them. They literally follow the snail right into its own home and clean it out. That sounds good until one realizes that if Gonaxis is to be liberated in numbers on some of these infested islands, it may not do any better job than in Africa, and may clean out all or most of the local snail fauna to boot. The same can be said for a giant African predatory carabid beetle, called Tefflus, whose introduction into Guam has recently been favorably considered by some authorities.

Some argue that we cannot afford to be sentimental about wiping out the local snail fauna when there is a chance of Achatina fulica being included on the list of Gonaxis and Tefflus. Thai would be good reasoning indeed if there were no other alternative. But there is. The field of chemical control of snails and slugs has scarcely been touched. Working with the specific attractant and toxicant metaldehyde as the base, there is no telling what more potent chemical might be found. We have only to turn to the apparently more attractive field of insect control to see what can be done with a little concerted effort — DDT and Chlordane being cases in point. Surely this chemical approach holds far grealer possibilities than the playing-with-fire biological control. The literature is replete with the sad tales of this latter type of control boomeranging and becoming a cure worse than the disease. For example, the mongoose in Hawaii is now a far greater pest, especially to poultry, than were the snakes for which the mongoose was brought in as a control. Need more be said?

The next question is, What is the danger to us in North America? Frankly, the situation is alarming. With salvaged war materials, produce, and tourists pouring in from Hawaii, the Philippines, Micronesia, and other infested areas, a grave threat to this country exists. Worst of all, with the possible exception of Arizona, California is the only slate in the Union that is properly alerted to this danger. And even California, long famous for its plant quarantine regulations, was not equal to the emergency until these snails had actually entered the state— not once or twice but several times.

There was brought into California only a few months ago salvaged war equipment which had remained in the jungles of infested areas long enough to become overrun with jungle growth. In this debris, under the seats and on the under sides of things in general, were countless Achatina fulica, even up to three inches in length. On arrival they left the jeeps, ambulances, and bulldozers and moved down the wharf area of San Pedro in search of some American food. Here they were discovered feeding and breeding, none the worse for the long trip. The state quarantine officers immediately threw a barrier around the infested area and literally drove the snails right into the Pacific Ocean — each time with complete eradication.

Now the California Bureau of Entomology and Plant Quarantine, under the able direction of its Chief, H. M. Armitage, has erected a paved strip of land both at San Francisco and San Pedro. All salvaged war equipment is rolled out onto these strips as it is brought ashore, and is treated with live steam under terrific pressure. So extensive is the steam treatment that the vehicles need scarcely more than a grease job before they are ready for use again.

An examination of the debris has revealed thousands upon thousands of Achatina fulica. Further, the California lawmakers, in full cognizance of the value of the quarantine regulations, have put into effect new regulations that empower the BEPQ to make this sort of inspection and treatment mandatory. The state is doing its darnedest, and virtually alone, to keep back the enemy.


QUITE a different situation is found in the U.S. Bureau of Entomology and Plant Quarantine. This Bureau has no regulations whereby it can demand similar treatment when loads come in to Eastern or other Western ports. Its regulations cover the banning of certain specific birds, mammals, and insects, but it does not have even a catchall regulation which would prohibit the entry of Achatina fulica. The best the Bureau can do when loads come in from snail-infested areas is to recommend and solicit the coöperation of both shipper and importer. So far, they have cooperated in the Bureau’s unofficial attempts to keep this snail from landing on the East Coast. But with such a loose modus operandi as this, one cannot hope for indefinite success.

Here is whore the real danger lies. There is in process a huge program of returning to both California and other U.S. ports between 500,000 and 1,000,000 tons of salvaged war material from regions where this snail abounds. Latest information from Washington indicates that there is no record of the interception of. Achatina fulica on the Atlantic coast! Yet it has been intercepted by the thousands in California. The implication shouts.

It is apropos to point out that the Japanese beetle, the Asiatic beetle, and other Oriental agricultural pests have entered the U.S. not through the near-by California ports but through Eastern ports. With these thoughts in mind, it is neither difficult nor reckless to predict that with the present setup, and in spite of California’s efforts, it is inevitable that Achatina fulica will get started in this country. It can spread wherever the ground temperature does not get excessively low for long periods in the winter. It would be especially bad in places like California, the Gulf states, and the Southeastern states. Its ability to aestivate or “summer hibernate” during the hot dry summers, as some of its close relatives do in regions adjacent to the Sahara, would even see it through in many purls of the Southwest.

A second and more subtile avenue of possible entry of Achatina fulica into this country is through the mails. Recall that the first specimen entered Hawaii by ibis means. There is no Federal postal regulation which can effectively cope with this danger. California and Arizona have state quarantine postal inspectors, but the very nature of packaged material has not so far permitted any real degree of efficacy. People will be attracted to these invertebrate giants and will send them as curiosities to relatives or friends.

And if you do not think this is an acute danger in this country, here is a recent case in point: Warren E. Buck of Camden, New Jersey, a wildanimal collector and importer of no small reputation, brought back with him from Nigeria over two years ago several live specimens of the largest species of all these giant snails, and the largest land snail in the world, Achatina achatina. This species attains a length just short of eight inches and gets as big around as a small saucer. But understand this: since there is no regulation prohibiting their entry, these were brought in legally.

A few months later, two live specimens were shipped through the mails to another well-known collector, Wesley H. Dickinson, of Selma and Long Beach, California. Again no Federal regulation was broken. California, however, has state regulations requiring the declaration of such imports to the local agricultural commissioner. There was a slip somewhere, for it was not until over a year later that they were quite accidently and fortunately discovered. They had been given to the Steinhart Aquarium in the San Francisco Golden Gate Park for a few weeks, which made it possible for them to be put on display.

Dr. Tracy I. Storer, Professor of Zoology at the University of California and a member of the State Committee on Alien Animal Importation, saw these snails while visiting the Aquarium. Here were peacefully alive in California the very snails they had tried so hard to keep out! Urgent word of the news was immediately dispatched to W. C. Jacobson, Assistant to Director of the California State Department of Agriculture.

A thorough investigation was soon started, with the result that both snails and eggs were destroyed by quarantine authorities. Now do not let the fact that these were not Achatina fulica foot you for one minute. To be sure, Achatina achatina apparently has never had the opportunity to show whether it can be as destructive in a foreign country as its cousin fulica — but it is a cousin. Cousin panthera, which Sir David Barclay introduced on Mauritius, is making life miserable on that island for fulica. Latest word indicates that it is outfeeding and outbreeding it in most striking fashion.

There is no getting around it. The danger is already here. We in the United States are next on the fulica list. These few dead “scouts" indicate to us that a real invasion of this country is imminent. We must set up our defenses with no further delay. Stringent Federal regulations must be enacted to permit the U.S. Bureau of Entomology and Plant Quarantine to demand, under penalty of the law, a thorough examination, and treatment if necessary, of all produce, tourist baggage, and salvaged war material originating in snail-infested areas and entering this country at any port. The mail hazard must be reduced through postal inspection, advertisement, and other means. Grants and fellowships must be established to foster a great expansion of research in the chemical control of snails. And the utmost caution must be exercised in proceeding with the exceedingly dangerous biological control.

Time is short. We still have time to act. You are the lawmakers. You must decide how soon we will act. You must take the responsibility for effective quarantine measures or for untold millions of dollars of damage to U.S. agriculture plus many more millions spent on control.