Snails are common garden pests that are part of the same family of creatures also claiming oysters, octopus, squid and clams, being part of the class Gastropoda. Snails are mollusks, with more than 60,000 species being known in the world. They vary from aquatic to land or freshwater mollusks and they can be differentiated by several characteristics, but when it comes to the most common species which play the part of the pest in your garden, you will see that snails are quite alike.
Description and distribution of snails
Most snails are grey, but their shells can range from white to brown or almost black, and be mottled or striped. The snail’s head has two pairs of tentacles; a large pair holding his eyes and a smaller pair beneath for smelling. His mouth is below the lower tentacles, and the slime gland is beneath the mouth. Snails have a very rough tongue (called a radula) and most also have thousands of microscopic teeth that they use to scrap against the food, which helps them rip it into small pieces. The snail’s shell holds his visceral hump, where the organs are located. The shell joins the snail’s body, providing him refuge when he’s disturbed.
As mentioned above, there are different types of snails, that can be separated into three main categories de pending on their habitat, and two categories, depending on the way they breathe:
- land snails;
- freshwater snails;
- sea/maritime snails;
and - those that breathe using a lung, that belong to the group Pulmonata;
- those that breathe using gills, that belong to a polyphyletic group.
Snails can be found in a very wide range of environments, including ditches, deserts, and the abyssal depths of the sea. Most often, though, snails can be found in places where humans also live. Although they do not particularly enjoy the heat, they can survive perfectly fine by finding refuge in the shade, and if they live in the desert, they compensate by simply spending the majority of their time inside their shells, which stops their moist bodies from drying out. Some species of snails even live underground, about 2.5cm below the surface, in which case the only time when you might see them is when it rains, as they are forced to come to the surface so that they do not drown. If food is scarce during the summer or spring months, snails also have the ability to bring their bodies into a state of hibernation, which allows them to conserve energy and food. This is also used to survive in difficult conditions such as extreme cold or drought.
Breeding and dietary information regarding snails
Due to the fact that they have a poor vision, snails both use their sense of touch when it comes to finding food. They are nocturnal animals, that also hibernate during winter and manage to survive due to the fat they stacked up during the year. Most of the species are herbivores, eating plants and vegetables, but also decaying plants, fungi, ground lichens and the aquatic species, consume algae. There are also land species and some aquatic ones that can also be omnivore or carnivores. Some species of aquatic snails are considered top predators because they can annihilate their pray in a flash, by using deadly venom that they inject through their radula. Marine snail venom is more potent than morphine, but acts differently, as it can be deadly even for humans.
Some species, such as the land snail, can cause damage to agricultural crops and garden plants, and are therefore often regarded as pests. They can consume up to 40 times their weight in a single day. Most species feed on a broad variety of organic materials such as leaves, lichens, mushrooms, various vegetables and fruits, different herbs, and seedlings, being considered pests as well.
Although snails are hermaphrodites, they do have to mate with individuals from their own species before laying their eggs. Once a snail has located a mate, they encircle each other and sperm is exchanged through their protruded genitalia. A few days later, they lay approximately thirty eggs in a hole in the ground, or beneath the cover of an object such as a fallen log. This can be done in different locations that comply with the necessary environmental conditions (the most important of which is humidity), such as a hole in the ground, beneath a fallen log, etc.
Garden snails bury their eggs in shallow topsoil primarily while the weather is warm and damp, usually 5 to 10 cm down, digging with their foot. Egg sizes differ between species, from a 3 mm diameter in the grove snail to a 6 mm diameter in the Giant African Land Snail. After 2 to 4 weeks of favorable weather, these eggs hatch and the young emerge. Snails may lay eggs as often as once a month. The snail’s shell develops while it is still an embryo; it is, however, very weak, and needs an immediate supply of calcium. Newly hatched snails obtain this by eating the egg from which they hatched. The cannibalisation by baby snails of other eggs, even unhatched ones, has been recorded. At this stage, the young are almost completely transparent and colourless. Their shell is usually slightly smaller than the egg they hatched from, but their length when out of their shell is slightly greater than the egg diameter. After a few weeks, the snails will begin to show their first tinge of colour, usually slightly blue, before they turn their adult colour. Roughly three months after they have hatched, they will look like miniature versions of their mature kin. They will continue to grow, usually for two to three years, until they reach adult size.
The general lifespan of most snails is around 5 – 7 years. Still, only a very small portion actually reach maturity, with the majority washed away by rain and water people use in their yards and gardens or eaten by predators.
Snails as pests
Both these two types of mollusks can become pests, whether in your yard and garden, or even inside your house. In large numbers, they can cause severe damage, consuming a lot of what has been sowed to grow. They can cause a lot of problems in industries such as agriculture and horticulture. This is because they feed on plants, destroying foliage much faster than it can grow, as well as fruits and vegetables, and they can also cause holes in the crop, making the items unsuitable to sell due to aesthetic reasons, as well as much more vulnerable to rot and numerous diseases.
As control measures, baits are the norm in both agriculture and the garden. In recent years, iron phosphate baits have emerged and are preferred over the more toxic pesticides, especially because domestic or wild animals may be exposed to the bait. It is of scientific interest that salt kills them by causing water to leave the body owing to osmosis but this is not used for agricultural control as soil salinity is detrimental to crops. Traditional pesticides are still used, as are many less toxic control options such as concentrated garlic or wormwood solutions. Copper metal is also a snail repellent, and thus a copper band around the trunk of a tree will prevent snails from climbing up and reaching the foliage and fruit. As alternative control measures, one can also use beer traps, diatomaceous earth, crushed eggshells, or coffee grounds sprinkled around the garden plants.
Snails have many natural predators, including members of all the land vertebrate groups. Invertebrate predators include decollate snails, ground beetles, leeches, certain land and even the predatory caterpillars. Different types of reptiles, such as snakes, frogs or lizards, even owls, ducks or vultures, and foxes and badgers are also some of the most common predators of these mollusks. Humans also pose great dangers to snails in the wild. Pollution and habitat destruction have caused the extinction of a considerable number of snail species in recent years.
On the other hand, they can also play an important role in the ecosystem, by eating fungi and decaying plant material. Or they can be used in gastronomy, considered to be delicacies in certain parts of the world. Snails are also of use in the cosmetic industry, where skin creams derived from species such as Helix aspersa (where research shows that secretions produced by these snails while under stress facilitate regeneration of wounded tissues) are sold for use on dry skin, acne, scars, and even wrinkles. Du to their use in certain industries, heliciculture, which is the farming of snails, has also developed in the last years.
All in all, despite their diverse positive use, snails can create serious problems, should they become pests and affect a garden. Preventive measures must be taken and control measures applied once you are already facing a snail infestation. You can find more details regarding this on our relevant articles about how to prevent a snail infestation and also, how to get rid of an infestation caused by these mollusks.
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