Giant African snail  (Achatina fulica)

The giant African snail has yet to be classified by the IUCN.

Classed as one of the world’s most invasive species, the giant African snail (Achatina fulica) has been introduced around the world from its native home in eastern Africa (2). In general, the shell of the giant African snail is a reddish-brown colour, with pale yellow vertical markings (2) (3), although colouration can vary depending on the surrounding environmental conditions (2). When fully grown, the shell of the giant African snail has seven to nine whorls, and is most often narrow and conical in shape; however, some individuals appear much broader and shorter, while others are much taller and more slender (2) (3) (4).  

The giant African snail naturally occurs throughout the coastal area and islands of East Africa, ranging from Mozambique in the south, to Kenya and Somalia in the north. It has also been introduced to many other areas of Africa, including Morocco, the Ivory Coast and Ghana (2) (5). Worldwide, the giant African snail has been introduced to the Indian Ocean islands, throughout parts of Asia (particularly in the South East and Pacific regions), and is also known to occur in the Caribbean and Australia (2) (5) (6).

Within its natural East African range, the giant African snail is often abundant in forest margins (5). Elsewhere, this species appears to be well adapted to modified habitats, including plantations, gardens and disturbed sites at low to mid elevations, as well as invading primary and secondary forests (2) (5). The giant African snail also occurs in agricultural areas, along the edges of streams and rivers, in scrublands, and in urban areas (4).

The giant African snail is a hermaphrodite, meaning that each individual has both male and female reproductive organs (2) (3) (4) (5). Courtship begins as soon as it encounters a prospective partner, with one individual approaching the other from behind, and mounting the shell. If the snail that has been mounted accepts the potential mate, it will bend its head backwards and begin to rock its body, and the pair will then proceed to mating (5). In order to reproduce, the two individuals must engage in a reproductive behaviour known as ‘reciprocal copulation’, where sperm from one snail is used to fertilise the eggs in the other, and vice versa (3) (4) (5). The eggs are usually laid between 8 and 20 days after copulation has taken place, although the giant African snail is capable of storing sperm for much longer, and the eggs are generally deposited in a nest that has been excavated in the soil, or among leaves and stones (4) (5). The number of eggs laid in each clutch depends on the age of the snail, although it is usually between 100 and 500 eggs. The young snails hatch after around 11 to 15 days, depending on the temperature and the local conditions (4) (7).

Mainly active at night, the giant African snail feeds on living or dead plant matter from as many as 500 different plant species, including many economically valuable crops such as cabbage, cauliflower, cacao and banana, as well as many others (2) (3) (4).

There are no known threats to the giant African snail.

In fact, the giant African snail is widely considered one of the worlds’ most invasive species, and has been listed among the “100 World's Worst Invasive Alien Species” by the Global Invasive Species Database (2) (4). It is illegal to import this species into many countries (2). Outside of its natural range, this snail is considered a major agricultural pest, and may also threaten native snails and ecosystems in areas where it has been introduced. It is also a carrier of several parasites, some of which are harmful to humans if ingested, while others increase the spread of plant diseases (particularly the black pod disease in cacao plants) (3) (4).

There are currently no conservation measures specifically targeted at this species. In some areas of the world where the giant African snail is considered to be a pest species, eradication programmes have been established to prevent further damage to crops and to native plants, snails and ecosystems.

For more information on the giant African snail and its role as an invasive species:

• The Asia-Pacific Invasive Species Network:
  http://www.fao.org/world/regional/rap/invasives/invasives/fact_sheet1.pdf