Heliciculture - Pens and Enclosures

Pens and Enclosures

The U.S. Animal and Plant Health Inspection Service (APHIS) Standards for Snail-Rearing Facilities were revised March 2001 and are available at

Enclosures for snails are usually long and thin instead of square. This allows you to walk around (without harming the snails) and reach in the whole pen. The enclosure may be a trough with sides made of wood, block, fiber cement sheets, or galvanized sheet steel. Cover it with screen or netting. The covering will confine the snails and keep out birds and other predators. Fences or walls are usually 2 feet (0.61 m) high plus at least 5 inches into the ground. Fencing made of galvanized metal or hard-plastic sheets helps keep out some predators. A cover will protect against heavy rain. Shade (which may be a fine mesh screen) on warm winter days helps keep the snails dormant. Use 5 mm mesh or finer for pen screens or fences. Pens containing baby snails will need a finer mesh.

Snails like hiding places, especially during the warm daytime. For example, purchase plastic soil drainage pipes from the local garden center, split them in two lengthwise, and stack one layer one way and the next layer at a right angle. This will provide shelter and will increase by 50% the number of snails you can put in the pen.

A sprinkler system will ensure moisture when needed. Turn it on at sunset. If turned on early in the day, the moisture may drive snails out into hot sunshine. Monitor temperature and humidity using a thermometer and a hygrometer.

Although you can use fencing for the enclosure's sides, the bottom, if not the ground or trays of dirt, must be a surface more solid than screening. A snail placed in a wire-mesh-bottom pen will keep crawling, trying to get off the wires and onto solid, more comfortable ground.

Preventing escapes: In an open pen, curve the top of the fences inward in a half circle to confine the vineyard snail. H. aspersa will escape from such an open pen, so you could use an electric fence to contain them.

Another technique to confine snails is to bend the fence top inward into a sharp "V" shape with about a 20 degree angle. The snail's shell will hit the bent-back part of the screen before he can reach up and start crawling on it. This blocks him, and the angled screen automatically compensates for the size of the snail.

Another alternative, especially handy for solid wall enclosures, is to attach to the wall a horizontal piece of screen that projects inward several inches over the enclosure. Make the screen with material like nylon monofilament that is moderately stiff and springy yet easily flexible. On the inside edge of the screen, remove the cross fibers until you've created a fringe several inches wide. As the would-be escapee crawls on the underside of the screen and moves out onto the fringe, his weight pulls several individual fibers down. One by one, another fiber gets away from the snail and springs back up out of reach. Eventually the snail is dangling by a thread. He then falls because the surface area is not big enough to crawl on.

Since snails usually will not cross a copper band, another solution is to top the fence with 3-inch-wide (or wider) copper band. You could bend the band so that part of it faces inward and is parallel to the pen floor. If the band is placed too close to the ground, rain may wash soil against the copper and leave a residue that may enable the snail to cross it. Also, be sure to bury the bottom of the fence deep enough into the ground so that the snails don't dig under it.

Pens with gardens: An alternate method is to make a square pen with a 10-foot (3.0 m)-square garden in it. Plant about six crops, e.g., nettles and artichokes, inside the pen. The snails choose what they want to eat. If it has not rained, turn sprinklers on for about 15 minutes at dusk, unless the snails are dormant. A disadvantage to this method is that, if the snails are not mature at the end of the year, it is difficult to replant fresh plant crops in the pens.

Plastic tunnels make cheap, easy snail enclosures, but it is difficult to regulate heat and humidity. The tunnel will be 10 to 20 warmer than the outside, and snails become dormant as the temperature climbs above 80 °F (27 °C).

Indoor pens: With snails raised indoors under controlled conditions, reproduction varies according to the geographic origin of the breeding stock. For example, one researcher found that H. aspersa snails from Brittany seem to do better indoors than snails from another region. To breed snails indoors, keep the temperature at 70 °F and the relative humidity at 80% to 90%; some sources say 95%. Another source recommends 75% humidity by day and 95% at night. The Center for Heliciculture once recommended 65-75% humidity during the day and 85-95% at night at 68 F. In any event, avoid humidity higher than 95% (some say 90%) for any length of time. Excessive humidity can kill snails. Optimum temperature and relative humidity depend on several things, including the snail variety and even where breeding stock was gathered. For H. aspersa, the optimum temperature for hatching eggs seems to be 68 °F (20 °C)at 100% relative humidity. The second best temperature/humidity combination depends on where the snails came from and results can drop drastically to 0% hatching at 17 °C (63 °F) and 100% humidity. Err on the side of a few degrees warmer or a small percentage dryer. Do not keep the soil wet when the humidity is maintained at 100%, as the eggs will absorb water, swell up, and burst.

Use fluorescent lights to give artificial daylight. Different snails respond differently to day length. The ratio of light to darkness influences activity, feeding, and mating andegg-laying. Eighteen or more hours of light apparently stimulate H. aspersa growth, while less than 12 hours inhibit it. Some snail species may associates the long hours of light with the start of summer—the peak growing season. Eighteen hours of daylight also appear optimal for breeding (mating and egg laying), but snails will breed in darkness.

Breeding boxes and cages: Snails can be bred in boxes or cages stacked several units high. Use an automatic sprinkler system to provide moisture. Breeding cages should have a feed trough and a water trough. Plastic trays that are a couple of inches deep are adequate; deeper water troughs increase the chance of snails drowning in them. These trays may be set on a bed of small gravel. Fill small plastic pots, e.g., flower pots about 3 inches deep, with sterilized dirt (or a loamy pH neutral soil) and set them in the gravel to give the snails a place to lay their eggs. Remove and replace each pot after the snails lay eggs. (Set one pot inside another so that you can easily lift one out without shifting the gravel.)

After the snails have laid their eggs, put the pots in a nursery where the eggs will hatch. Keep the young snails in the nursery for about 6 weeks. Then move them to a separate pen as young snails do best if kept with other snails of similar size. Eight hours of daylight is optimal for young snails.

The following is an example of starting H. pomatia in boxes: Build wooden boxes measuring 25 by 35 cm and 25 cm high. Cut a 6 cm-diameter hole (to drain excess moisture) in the bottom and cover the hole with plastic screening, well secured. Cover a frame with plastic screening to create the box lid. The lids either must open or be removable. Keep the boxes on shelves so they are easily accessible. Fill the boxes one-third full with loose, uncompacted garden soil baked to kill all organisms (insects, nematodes, bacteria, etc.). Partially cover the soil with moss, but leave enough room for the snails to crawl around on the dirt. Sprinkle water on the moss.

Move to boxes (three per box) those snails in the outdoor pen that are starting to make holes in which to lay their eggs. After the snails lay eggs, return them to the outside pen. The soil in the boxes must not dry out. Always keep the moss slightly moist. Too much moisture is dangerous, however, as the eggs may swell up and burst. The eggs hatch in about 25 days, but the baby snails remain in the egg "shells." They then work their way out of the nest for about 10 additional days before they appear on the moss and on the sides of the box. Snails on the wood sides of the box are in danger of drying out and must be carefully removed and put on the moss. Shells are very fragile at this time.

Feed the baby snails tender lettuce leaves (Boston type, but head type is probably just as good.)

Three weeks after the snails appear on the moss, carefully remove the baby snails and put them together in a temporary container. Carefully remove the moss and dirt, watching for any more baby snails. Replace the dirt and moss with fresh (sterilized/baked) dirt and fresh moss. Count and return the snails to the box.

The young snails can be kept over winter in these boxes. Stack the boxes in a cool room protected from frost. The room should never get colder than 0 °C nor warmer than 3 °C (32 °F to 37 °F). Snails will become active again the following spring when the temperature rises above 5 °C (41 °F). Feed them for 4 weeks. They should now average about 8 mm. Move them to a pen, carefully clean and dry the boxes, and prepare the boxes for the new season. H. pomatia matures in 18 months to 4 years.

Mixed system: A variation of the method above is to let the snails lay the eggs in the outdoor pen, then carefully transfer the eggs to the boxes. In the pen, look for snails that have dug holes and are in them laying eggs. The tip of their shell will be visible. Stick a marker in the ground next to the hole. When the snail is finished and leaves, use a garden trowel to dig up the eggs and move them. This task is difficult. The eggs can be both physically damaged and covered with dirt.

Example: Five stages of snail raising

Some who raise H. aspersa separate the five stages: reproduction, hatching, young, fattening, and final fattening.

In a typical example, the breeding box has concrete sides, soil with earthworms (to cleanse the soil) on the bottom, vegetation, curved tiles to provide shelter, feeders, and a chicken waterer. Mosquito netting or screening covers the top. These breeding boxes may be outside, or you may get better results when the boxes are inside a greenhouse—as long as the greenhouse does not get too hot or too dry. One researcher reported that in outdoor boxes, each breeder snail had about seven young. In greenhouses, each breeder snail had about 9 to 12 young. The researcher felt that under better weather conditions than those he had that year, each adult breeder snail would have produced 15 young snails.

Fattening pens may be outside or in a greenhouse. High summer temperatures and insufficient moisture cause dwarfing and malformations of some snails. This is more a problem inside greenhouses if the sun overheats the building. A sprinkler system (e.g., a horticultural system or common lawn sprinklers) can supply moisture. Make sure excess water can drain.

Fattening pens may contain 2-foot (0.61 m) by 3-foot (0.91 m) pieces (or other convenient size) of heavy plastic sheets, hung from boards resting on a rack that lets the tips of the plastic sheets just touch the ground. The plastic sheets are about 4 inches apart. The sheets give the snails a resting and hiding place. Feeders may be located on the rack that supports the plastic sheets.

Put a layer of coarse sand and topsoil with earthworms on the fattening pen's bottom. The worms help clean up the snail droppings.

You can put snails that hatched the previous summer in a chilled room for hibernation over winter. Then, about the 1st of April, (adjusted for your local climate), move them to the final fattening pen. If you have several fattening pens, put the smaller snails in one, medium in another, large in another. Do not exceed one-third pound of H. aspersa snails per square foot of pen. Since snails lose weight when they estivate in summer, some growers do not stock pens by weight but by count. For H. aspersa, 10 to 12 snails per square foot is about the maximum.

Breeding pens can be set up just like the fattening pens or the fattening pens can be used as breeding pens after you harvest the mature snails. Harvest some snails and leave some to breed.