The garden snail (Cornu aspersum) is one of the most widely recognized land mollusks. This gastropod is frequently encountered in environments shaped by human activity, particularly in gardens, agricultural fields, and urban green spaces. Its presence is common across many temperate zones, making it a familiar sight worldwide. The shell of an adult snail is typically brownish-golden, marked with darker, often interrupted, spiral bands.
Global Presence and Spread
The garden snail is historically native to the Mediterranean Basin and Western Europe, ranging from Northwest Africa and the Iberian Peninsula north to the British Isles. However, this species has become cosmopolitan, meaning it is now found on every continent except Antarctica. This extensive distribution is primarily a result of human activity, a process known as anthropochory.
Humans have transported the snail both intentionally (e.g., introduced to California in the 1850s for use as a food source) and accidentally, often hidden within shipments of plants or agricultural goods. The garden snail is now naturalized in regions with climates different from its native Mediterranean home, including North America, Australia, New Zealand, and South Africa. In many of these new territories, it is often classified as a garden or agricultural pest due to its wide range of plant hosts.
Essential Microhabitat Requirements
For its daily survival, the garden snail relies on specific microhabitat conditions that protect its soft body from desiccation. Because its skin is highly susceptible to water loss, it must seek out environments with high relative humidity, ideally ranging between 70% and 90%. This need for moisture explains why snails are most active at night, in the early morning, or immediately following rainfall.
During the day, they retreat to cool, shaded locations to avoid the direct heat and drying effects of the sun. Preferred shelters include damp, dense foliage, under rocks, beneath logs or garden debris, and even in crevices in walls. Snails also require a source of calcium to maintain and grow their hard shells. They obtain this mineral by consuming calcium-rich matter in their environment, such as decaying organic material, soft soil, or even concrete and crushed shells.
Surviving Extreme Conditions
When environmental conditions exceed the snail’s tolerance for heat or cold, it enters a state of dormancy to survive. During periods of hot, dry weather, the snail undergoes aestivation, which is a form of summer dormancy. When temperatures drop and winter arrives, the snail enters hibernation to survive the cold.
The snail secretes a thin, protective membrane of dried mucus called an epiphragm across the aperture of its shell. This structure, which can contain calcium carbonate, significantly reduces water loss during aestivation and insulates against cold during hibernation. The snail typically seeks out a sheltered location called a hibernaculum to endure these extremes, such as burrowing deep into the soil, clustering in protected crevices, or adhering to vertical surfaces like fences and walls. By slowing its metabolism and sealing its shell, the garden snail can survive for months, and occasionally even years, until favorable, moist conditions return.