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Giant African Land Snails

Biology

In many parts of the world the Giant African Land Snail (Achatina fulica) is a serious native or introduced pest to agriculture. As its name suggests, it is a large land-living snail that was originally native to East Africa. There are also other species of large terrestrial snails from Africa that are now bred in the U.K.: Archachatina marginata and Achatina achatina originate from West Africa and are becoming increasingly common. Achatina fulica is, however, regarded as the ‘Giant African Land Snail’, more for its notoriety than anything else. In many respects the giant snails show few differences in appearance when compared with the snails commonly found in British gardens. They do, of course, grow to a much larger size and in general have a more pointed form to the spiral of the shell. The foot also spreads out further when compared with native species.

• Achatina fulica is the largest and commonest giant African land snail, and although originally from East Africa is now distributed throughout the tropics. It may reach maturity in captivity in just over one year but this can take four or five years in the wild. It lays small yellowish white eggs about 4 mm in diameter. With a shell length averaging in adults at 250 mm the snail weighs about 250 grams. The shell is a brown colour with weak darker markings that appear as bands across the spiral. The mantle, the fleshy part inside the shell through which the foot protrudes, is a pale yellowish colour. The columella, the smooth inner surface to the opening of the shell is also yellow. The ‘head’ portion of the foot is light brown but the rest of the foot is paler with thin net-like markings.

• Achatina achatina grows to about 200 mm and has a much more patterned shell than A. fulica the shell is slightly more yellow with distinct brown jagged bands. On the shell can be seen striations that are distinctly and regularly broken. The columella is purple and the eggs are about 6 mm in diameter and obviously yellow in colour. This species comes from West Africa from Liberia to Nigeria.

• Archachatina marginata is again about 200 mm when full grown. The shell is much less pointed than the Achatina species and this ‘roundness’ is especially obvious in young animals. The columella is white and the eggs are comparatively large at 17 x 12 mm. The striation on the shell may give the appearance of a ‘woven’ texture, especially when looked at under a magnifying lens. The head is a dark grey but the rest of the foot is a lighter shade. Its ranges from Zaire to the Ivory Coast. The snails’ ability to eat virtually any form of plant material combined with their capacity to build up large populations rapidly, means that they can be serious agricultural pests. Indeed, in suitable habitats the snail is able to maintain populations averaging 150 per square meter.

Achatina fulica has been introduced into a number of tropical eco-systems in the Far East and Pacific islands, sometimes by accident but also deliberately. In 1928 the giant African land snail was introduced into Sarawak as poultry food and during the Second World War the Japanese forces took the snail as human food to New Guinea and other occupied territories, Related West

African species are also extensively used as a food source. In Ghana, for instance, they constitute the greatest single source of animal protein.

In Europe and North America the snails are also eaten, but in up-market gourmet restaurants. The traditional European species of ‘escargot’ is relatively small and slow growing, so the demand for snail meat has been partially satisfied by the flesh of the giant African land snail, ‘Escargot achatine’. The commercial success of farming and ranching ‘Escargot achatine’ may be appreciated by the observation that as far back as 1977 over 1,500 tons of canned snail meat, worth U.S. $3 million, were shipped to Europe from Taiwan alone. The giant substitute is said to be slightly inferior to the edible European snails as it is ‘rubbery’ and too often ‘swampy-tasting’. When highly flavoured with garlic, chopped and stuffed into the shells of genuine escargot, however, most of the people eating the African snails are effectively deceived. Although these maintenance notes have been written specifically for giant African land snails, most of the essential details apply equally well to other species of terrestrial snail or slug, including native British species. Native species, however, will only thrive if they are kept in conditions below room temperature. A north-facing windowsill, in an unheated room, will often be suitable.

H ousing

The Giant African Land Snail can be housed in many types of container but all of them must be able to withstand the warm humid conditions that are necessary. An aquarium or plastic pet cage would make a suitable home and one sized 40 cm x 25 cm x 25 would house an adult snail or several smaller specimens. An escape-proof (but not airtight) top is necessary and preferably one that allows for some ventilation. A sheet of glass or perspex, slightly raised on small pieces of Plasticine, will often suffice to seal the container for small to medium specimens. Larger animals are quite strong and will require a more secure lid. Purpose- built metal tops for aquaria (with space for a Basking Spot Lamp fitting) are available. There also needs to be some method of general heating. A Habi- Stat™ heat mat taped to the rear wall would provide most of the heat needed but could be supplemented with a small Basking Spot Lamp for daytime use in the larger cage. Although providing heat from a light source is convenient, it does have one drawback. The snails are mainly active in darkness and it is then that they feed most readily. Thus in bright light the snails feed less and grow more slowly. A coloured lamp could be used, but if not, it will be necessary to accept the snails’ inactivity and slower growth. A temperature of between 25ºC and 30ºC should be aimed at. The base of the container should be covered with some sort of substrate and Rain Forest Substrate will stand up to the warm damp environment without rotting. Alternatively, sphagnum moss peat could be used. A layer about twice the width of the largest snail housed will give sufficient depth for the animals to burrow. A light misting may be appreciated, as high humidity may be an essential factor. Snails should be able to freely approach water, usually provided in a water dish. This they may drink or simply ‘wash’ themselves. The environment should also contain other surfaces over which the snails can move. Cork bark logs will offer softish but irregular surfaces and as they are hollow, will double as convenient hides. A limp of chalk or limestone is the other essential cage furnishing. Snails have a huge requirement for calcium to build the shell, so this mineral is very important. Note that ordinary ‘blackboard’ chalk should not be used, as this is not calcium carbonate. Do not use live plants to decorate the tank as they will be eaten or severely damaged.

Husbandry

Snails can be kept in groups, usually of similar sized individuals but sometimes different sizes will live together if not too crowded. Many will just sit motionless for most of the day, so plenty of flat smooth should feature in the cage design.

These animals do not really like being handled, so if it is necessary to move them, pick them up by grasping the base of the shell. If the body is extended and gripping a surface, it may be a little difficult to lift them. In such cases, slide a finger under the foot to release the vacuum that attaches them to the surface. The growing margin may be especially thin and it is best not to touch this area at all. To induce a contracted snail to emerge from its shell, it can be placed in a little tepid water for up to ten minutes (but not much longer). Be very careful to wash your hands before and particularly after handling these creatures. As with many mollusks, there is a slight possibility of Salmonella bacterial contamination. This is particularly true if the snails are not cleaned out regularly.

They have two basic defenses. One is to play dead and retreat into their shells. The other is to produce copious amounts of slime. It is best not to irritate them into this action, as the secretion is very sticky and difficult to clean off. However revolting the slime is, it is not harmful to humans and is intended to ‘gum up’ potential predators not poison or chemically corrode them.

Food & Feeding

Giant African Land Snails will eat a huge variety of food. In the wild they mainly eat fresh or rotting leafy vegetation but any sort of fruit, salad or other vegetable matter may also be offered. As pets they will also tackle bread, cooked meat and sweet milky foods like puddings; in fact just about anything you care to offer them. This is not to say that everything is good for them. The food should remain in the cage for a reasonable time without rotting or causing a smell. Also, if a lot of loose, wet food is consumed, the snails’ waste droppings tend to be rather foul. A good diet for pet snails that will also last for some time without causing offence is a mash of rabbit pellets mixed with about 10% Repti-Sand as a source of calcium carbonate. This paste will last for a couple of days without deteriorating. Food should always be available. Water is occasionally sipped from droplets on the leaves but if a moist diet is offered, drinking water is often ignored.

Reproduction

Snails, like many mollusks, are hermaphrodites that are all individuals carry both sex organs. They mate with each other and both animals go on to lay eggs. Mating is proceeded with a courtship that involves the suitor piercing the body of the other individual with a stimulating dart. This can sometimes be seen as a white splinter sticking out of the skin. The eggs that are usually concealed in a buried chamber. Giant snails begin breeding when about a year old. Eggs are deposited 40-500 at a time, in or on the soil every two or three months. The young hatch usually within ten days. A single snail, by presumably storing sperm after mating, can lay eggs months after isolation and can found a complete colony. Once eggs are laid it is advisable to remove them carefully using a spoon or something similar and place them in a small tank on their own, the small tank being a miniature of the adult container. Removal of the eggs will avoid damage to them and to the small young snails as they hatch. Not much information is available on these pets but a few booklets have been published. There is even some interesting facts and pictures on the Internet.

Health & Disease

These snails seem to be relatively disease- free; certainly their resistance to most ailments has contributed to their success. Records show that the giant African land snail can live for over nine years in captivity. As the snails can have periods of inactivity, sometimes lasting up to a year, it is difficult to draw precise conclusions about the snails’ longevity.

Not much is known about the natural diseases of these animals but it is thought that they can catch infections from native species. This makes it inadvisable to keep African and British species together as there are reports of tropical snails dying when housed alongside native species. The snails also die if kept too cold or too dry.