There are approximately 1500 species of land snails and slugs in Eastern Australia. Most snails found in urban gardens are introduced species, the common Garden Snail was introduced from Europe in early 1800s. Native snails are usually restricted to natural habitats and unlike the introduced species do not adapt well to environments disturbed by human activity.
A snail has a hard calcareous shell which it creates by releasing liquid from its body which hardens and acts as protection for its soft body. Over time the snail releases more liquid and this allows the snail to gradually increase the size of its shell as it grows. Because snails are so slow they rely upon their ability to retract their body into their shell to escape predators.
Snails require a moist environment and have adapted to conserve water. The body of a snail is covered by a slime that is described as hygroscopic i.e. it attracts water, the slime coating and thick muscular mantle reduce evaporation and its ability to close its breathing hole controls air flow and water loss through exhalation.
Snails have one or two pairs of retractable tentacles depending on the species. They have invertible eyes located at the tip of the tentacles which can be maneuvered to provide expansive vision; the tentacles also contain chemical, olfactory and tactile senses.
Snails move slowly. Their locomotion is by use of a long muscular organ called a foot which spreads out under the snail's body. The muscle ripples along the ground, as it moves it secretes slippery mucus which coats the ground to reduce friction and maintain body hydration. The slime has remarkable properties, it is both slippery and sticky, so while it helps a snail to slide over the ground it also enables a snail to stick to a surface so that it can travel over any terrain and can even negotiate extremely sharp objects without harm.
If conditions become hot or dry, snails can enter an inactive state called aestivation, when it becomes too cold they hibernate. In both dormant states snails retreat into their shells and seal the opening with a mucous membrane that leaves a small hole to allow the snail to breathe.
The diets of snails depend upon the species; they may be carnivorous predators, herbivorous or omnivorous scavengers. Snails eat by grinding, grating and tearing their food with hard tongue like organs called radulas which are covered by rows of thousands of tiny teeth.
Most terrestrial snails are hermaphrodites which possess both male and female organs. After courtship and mating both individuals lay eggs in small holes which they cover with dirt and slime. After a few weeks the baby snails hatch, they have soft shells and most fall victim to predators before reaching maturity at approximately two to three years old.