Slugs and snails, the gardener’s fiends

 

Slugs and snails, the gardener’s fiends

                            White-lipped snail (Cepaea hortensis)

It is just emerging from its shell, its horns poking out

Why is it that slugs are so repulsive while snails are quite appealing? After all, they are effectively the same animal, the obvious difference being the slug’s lack of portable accommodation, although some slugs have an internalised soft shell, which is used to store minerals.

Both are gastropods in the classification of molluscs, belonging in the same family as clams, oysters, and other shellfish. They have one muscular foot by which they move, aided by the mucus secreted from glands. Not only is the slime a lubricant, it also acts as a kind of fixative, which allows them to climb up vertical surfaces and not crash to the ground. Slugs evolved from snails, in much the same counterintuitive way that snakes evolved from lizards.

Their most noticeable retractable tentacles are the ones that end in eyes, the other less evident ones being used to sense the surface they are moving across. Slugs and snails have poor eyesight, though they can tell the difference between light and dark, meaning that they can navigate towards darker, safer places. They rely on taste, smell and vibrations to find food and potential mates.

Snails live for two to three years in the wild, but may live longer in captivity.

In cold weather, snails hibernate in sheltered places, like drain covers or plant pots, sealing the entrance to their shells with mucus.

Slugs live for six to twelve months, exceptionally about eighteen months, and do not hibernate. They lay eggs in the autumn which hatch in the spring. Mature slugs burrow underground if the temperature falls below 5˚C (41˚ F) although they can withstand freezing for a short period.

In extremely hot periods, both slugs and snails aestivate, which is a kind of summer hibernation.

Gardeners attempting to foil the depredations of slugs and snails employ many deterrents, like beer traps, copper wire, cloches, or grit. Strongly aromatic plants, particularly herbs like rosemary or thyme, mint, or basil, deter the gastropods because they dislike strong smells.

 However, these animals also serve a useful purpose in clearing the ground of dead leaves and corpses and dung, returning nutrients to the soil. They are also a valuable food source for birds, reptiles and mammals like badgers and foxes.

There is one species of snail that is protected in England and Wales under the Wildlife and Countryside Act of 1981. Anyone contravening the act, even handling a dead snail, is liable to a fine of £5,000 or six months in jail. It is illegal to handle them without a licence.

Roman snails (Helix pomatia) are about the size of a chicken’s egg, almost twice as large as a garden snail, and are long-lived, attaining ten to twenty years of life. They are the escargots of French cuisine and were introduced by the Romans, as a source of food. Numbers were greatly increased by mediaeval monasteries in England cultivating them for food. They are widespread in southern England, principally in the Chilterns, the North Downs, the Cotswolds, and the borders of the Mendips, all of which are largely chalky areas, but are most uncommon in suburban gardens.

The law was enacted because by 2008 some of the populations of Roman snails had been reduced almost to extinction by people collecting them to eat, either in domestic settings or in restaurants.

Roman snail (Helix pomatia) empty shells 

Image courtesy Wikimedia Commons

I found this rather haunting Australian Aboriginal poem in a book of children’s poetry.

SNAILS

Sound of snails – crying

Sound drifting through the brush, sound of crying

Slime of snails, dragging themselves

Along the low-lying plain, crying;

Snails with their slime, crying.

Sound drifting through the bush: dragging themselves along, crying,

Snails, their sound blowing overhead from among the bushes.