The Tale of the Roman Snail

A Roman Snail on a mossy tree.

Inconspicuous gastropods glide through our garden soils and along our sidewalks, emerging particularly in dewy mornings or drizzling rain. Topped by their delicate shells or seemingly unhoused, these slimy creatures go about their day at a much slower pace— gliding between our feet on a damp sidewalk, clinging to a leaf, or traversing our gardens.

Snails and slugs are both terrestrial gastropod molluscs which are not formally differentiated. Generally, those lacking an external shell or with a comparatively small shell compared to their body size are considered slugs, whereas snails are those with an adequately large shell [1]. With a beige body, the Roman Snail (Helix pomatia) adorns a round, brownish shell with 3-5 light brown bands and 4-5 whorls that reaches approximately 4-5cm or 1.5-2in in diameter [5,4].

The Roman Snail was first classified by Carl Linneas in 1758 [2,4]. Although native to central and southeast Europe, humans have spread Roman Snails across Europe, Asia, and the Americas. Often being nocturnal, Roman Snails require mild, humid environments, avoiding heavy rain or direct sunlight. While they prefer low-lying limestone and chalk areas, they also frequent gardens, vineyards, and thickets. In the cold winter months, snails will dig a hole in the soil and lay shell-mouth up, secreting a mucus covering called an epiphragm that seals themselves within their shells during hibernation [5].

While foraging, Roman Snails secrete slime to traverse various surfaces, leaving a slime trail behind. To prevent drying out, they also use a particular part of their foot sole to "jump" forward [5]. After a foraging journey, the snails will follow their slime trail back home and return to the food they discovered the following day. Feeding most often occurs at between dusk and midnight, using their minute toothed tongue to brush food into their mouth. While they need calcium rich food to grow and maintain their shell, they also feast on the flowers, leaves, fruits, and vegetables of various plants [5]. As a generalist herbivore, the Roman snail selects its next meal based on the local density of plant species, essentially choosing whichever plant is readily available and avoiding very few plant species [2].

Terrestrial snails are in danger of drying out while feeding — especially in the intense summer heat— as they are not fully protected by their shell [2]. Although their slime can act as a deterrence, their predators include birds, mice, toads, and insects [5]. However, they have long been a culinary delicacy enjoyed by peoples of the past.

Heliciculture, or snail farming, is a branch of agriculture that was heavily practiced in Roman times. Loads of discarded snail shells have been excavated around ancient Roman settlements [3]. While some scholars believe eating snails may have been eaten only by the Roman elite, others think all people would eat snails as they were nutritious and readily available in nature [6,3]. While the practice of eating these molluscs occurred much earlier in many regions, the Romans’ taste for snails led to the spread of the now accordingly named Roman Snails all across Europe [3].

Aside from personal snail foraging, heliciculture developed where snails were fattened with flavorful herbs and traded. In the Middle Ages, snail gardens were kept at many monasteries, particularly in the Swabian Mountains of southwest Germany, where monks would cultivate the snails as an alternative to fish or meat during Lent. Swabian snail merchants would send boats holding 500 tonne barrels of snails down the Danube River to Vienna, where the barrels would then be returned over 373 miles (600km) by foot. This trade between Swabia and Vienna continued into the 1700s, but eventually Paris became the new great importer of these mollusc morsels. By the 1900s, the Swabian snail trade largely came to an end due to modern conservation efforts. While snails are considered a delicacy, 18th and 19th century peasants would eat snail dumplings, sausages, or snails with horseradish and cabbage. Most culinary snails are now imported from Eastern Europe, Africa, and Asia [3].

Thanks to conservation efforts, Roman Snail populations are less threatened by commercial collection— their current greatest threat is habitat destruction [4]. While some snail species— including the Roman Snail in some regions— may be of conservation concern, at a local scale snails and slugs can act as pests to cultivated plants and crops [2], particularly in temperate regions around the world. Across many countries including the U.S., the U.K., France, Ireland, and the Netherlands, individual species can cause millions of dollars of loss due to infestations, having devastating effects on agricultural production and economic profit of crops like legumes, cereals, rapeseed, vegetables, and fruits [1].

Unfortunately, chemical molluscicides are commonly utilized to control slug and snail populations, which are often not native species to the region. These chemicals, including metaldehyde or iron phosphate, can harm nontarget organisms and pollute water systems, which has led to efforts to ban metaldehyde in some countries. Due to their devastating impact on crops, the need to control non-native and pest snail populations is apparent. As a solution, biocontrol agents (spiders, rats, frogs, lizards, beetles, centipedes, millipedes, mites, flatworms, etc.) or bio-rational control agents (essential oils like garlic or spearmint, caffeine, plant extracts, etc.) could be utilized to avoid the use of toxic chemicals. However, the optimal control agents are still being researched [1], as it is important to be cautious to avoid causing more damage when hastily applying a solution.

I hope you enjoyed learning about these slimy little creatures with me. You likely would not come across a Roman Snail in Pennsylvania. Even though they have been spread across the world, they have only been found in small populations in the Northeast and in states like Illinois, Michigan, and Wisconsin— which is a good thing as they are a non-native species [7]! Regardless, I hope you can appreciate the history and impact of the Roman Snail, and I hope you can take a moment to appreciate any snail or slug as your paths cross on a dewy day.

Roman Snails (1,2) and other snail species (3,4,5) in southwest Germany. While not readily apparent in these photos, Roman Snails are quite a bit bigger than the other snail species pictured. (Photos by Faith Forry)

Written by Faith Forry — October 29, 2024

[1] https://www.mdpi.com/2075-4450/12/6/541

[2] https://www.tandfonline.com/doi/epdf/10.1080/00222933.2023.2203335?needAccess=true

[3] https://www.molluscs.at/gastropoda/terrestrial/helix.html?/gastropoda/terrestrial/helix/history.html

[4] http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/species?id=812

[5] https://animaldiversity.org/accounts/Helix_pomatia/

[6] https://publichistory.humanities.uva.nl/blog/my-roman-empire-snail-eating-and-elitism-in-ancient-times/

[7] https://heliciculture.us/about/