SVW #0: Gary The Snail Returns!
The is a park ‘n’ grab cache hidden along the access road for the Silvermine Valley Walk off Ou Kaapse Weg. For this reason, although it is not actually along the route of the walk itself, it is included in the series.
It was placed in acknowledgement of a previous cache at this location, family Behrens’ popular GC4FDGG Gary The Snail which was hidden on 2/7/13 and archived on 11/6/22 after 135 finds, garnering 7 FPs in its almost 9 year lifespan.
Gary the Snail is SpongeBob SquarePants’ primary pet who lives with him in their pineapple house. Known for his intelligent behaviour and ‘meow’ sounds, Gary acts as the underwater equivalent to a cat! This is all in an American animated comedy TV series which first aired in 1999 and chronicles the adventures of SpongBob and his aquatic friends in the underwater city of Bikini Bottom.
Snails are small, soft-bodied invertebrates that belong to the class Gastropoda, which is part of the phylum Mollusca. They are characterised by a coiled shell, a muscular foot used for movement, and a soft body that must remain moist to survive. Snails move by gliding along surfaces using waves of muscular contractions in the foot while producing mucous, which reduces friction and helps them travel over rough or sharp surfaces without injury.
Most land snails have two pairs of tentacles on their heads. The longer pair contains the eyes at the tips, allowing them to detect light and movement, while the shorter pair helps them sense smells and chemicals in their surroundings. These senses help snails locate food, find mates and avoid predators.
Snails play an important ecological role in many ecosystems, including the fynbos of the Cape Peninsula. They are mainly detritivores and herbivores, meaning they feed on decaying plant material, fungi, algae and sometimes living vegetation. By breaking down organic matter, snails contribute to nutrient recycling, helping return minerals to the soil where plants can reuse them.
In natural areas such as Silvermine they live in moist microhabitats such as under rocks, in leaf litter, or among dense vegetation. The Mediterranean-type climate of this region, with cool wet winters and dry summers, strongly influences snail behaviour. During dry periods many species enter a state of dormancy called aestivation (‘summer sleep’) sealing themselves inside their shells with a thin layer of mucus to prevent water loss (see here for a fascinating short video of waking a snail up). If conditions are too dry or cold, some land snails can hibernate for up to 3 years until conditions improve.
Although often overlooked, they are an important part of food webs, providing food for birds, small mammals, reptiles and insects. Because many species are sensitive to environmental change, they are also useful indicators of ecosystem health. Their presence and diversity often reflect the condition of soils, vegetation and moisture levels in natural habitats.
Some QI snail facts . . .
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There are over 70,000 snail species – c.35,000 land snails, c.30,000 sea snails and c.5,000 fresh water snails. 1,000s of others are still undiscovered, especially in tropical forests and deep ocean habitats.
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A snail’s mouth has a radula - like a tiny ribbon covered with teeth. Some species have >20,000 microscopic teeth used to scrape food off surfaces.
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Most land snails are hermaphrodites - having male and female reproductive organs, so two snails can both lay eggs after mating.
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The fastest snail ever recorded reached 0.05 km/h.
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Marine snails in the Cone Snail group can inject venom using a harpoon-like tooth. Some species are dangerous enough to harm humans.
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Some snails can regenerate damaged tentacles and other body parts.
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Fossils show snails existed during the Devonian Period >400 mya, long before dinosaurs appeared.
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Largest Snail: Syrinx aruanus (Australian trumpet) lives in the waters around Australia, Indonesia, and Papua New Guinea, can reach 91 cm in shell length and may weigh up to 18kg with the animal inside
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Edible Snails: up to 50,000 tonnes are eaten annually (approx. 5 billion snails @ average weight of 10g). France consumes around 40% of this total. Other large consumers are Spain, France, Italy & Portugal.
One of the most common snails found in coastal areas of the Western Cape, including Silvermine, is the white garden snail aka dune/sand hill/white Italian/Mediterranean (coastal) snail (Theba pisana) which originally comes from the Mediterranean region but has spread to many other parts of the world, including South Africa, Australia and the United States. It is an edible, medium-sized, air-breathing, land snail - a terrestrial, pulmonate, gastropod mollusk in the family Helicidae, the typical snails.
It is particularly well adapted to dry coastal environments and sandy soils. Although not native to the Cape Peninsula, it has become a familiar part of the local invertebrate fauna. It was introduced into South Africa prior to 1881 and has invaded the fynbos biome. Given the very high densities can be reached at some sites – it can reach up to 700 snails per sq.m - plus its apparently not particular feeding habits, its potential impact on the vegetation is cause for concern and needs further investigation.
In South Africa, it appears to have an annual lifecycle, breeding in autumn to winter and growing to adult size of about 14 mm diameter by the end of the following summer. Maturity is reached at half maximum shell size after 1 year with maximum shell size attained after 2 years. This species of snail makes and uses love darts (see image below) which are fired at each other by snails prior to mating. It is active mostly at night and especially during periods of high humidity, irrespective of temperature.
Its shell is usually small, rounded and typically cream or white to yellow-brown in colour with brown spiral bands - the species is known for having great variation in shell colour between individuals. The light colour of the shell helps reflect sunlight, which reduces heat absorption and helps the snail survive in hot conditions.
A distinctive behaviour of the dune snail is its tendency to climb vegetation, fences and other vertical surfaces during warm weather. Large groups of snails may gather on plant stems or shrubs, sometimes forming clusters. This behaviour helps them avoid the extreme heat of the ground surface and reduces water loss. During dry periods they become inactive and seal the opening of their shell with a thin mucus layer, allowing them to survive until conditions improve.
It feeds mainly on plants, algae and decaying vegetation. Because it can consume many types of plants, it may become an invasive species and serious agricultural pest in areas where populations grow very large. In addition to the direct negative effect of it feeding on agricultural crops, it also uses the stalks of cereals as aestivating sites, which in turn clogs machinery and fouls produce during mechanical harvesting.
In natural habitats such as Silvermine however, the snail can also contribute to ecosystem processes by helping break down organic matter and recycling nutrients in the soil.
The species reproduces by laying small clusters of 2.2mm diameter eggs in moist soil. Under favourable conditions these eggs hatch into tiny snails that gradually develop their shells as they grow. Because the life cycle can occur relatively quickly, populations can increase rapidly after rainy seasons.
See here for more information on this exotic gastropod.
