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Snails’ Deep Slumber

Hibernation is convenient when you live in a shell

Wiggling antennae poke out from under coiled shell of the second-most prolific species on earth, the gastropodal snail. On land and in oceans and freshwater, 43,000 snail species live. North America has 500 land species, which brings them, usually stealthily, to all our gardens.
    But you won’t see them this time of year, for many snails hibernate from October until April. Hibernation is convenient for snails as they carry their beds on their backs. In dry areas, snails can hibernate for years.
    Covering their bodies with a thin layer of mucus to prevent drying out, snails live off the stored fat in their bodies. They dig a small hole in the ground and bury themselves or find a warm patch to slumber the winter away. Then, they close off the entrance of their shells with dried mucus — called an epiphragm — that hardens into tough skin. This snail-made mucus door prevents predators from harming them during hibernation and keeps them warm and cozy all winter.
    The epiphragm is usually transparent and sometimes glues the snail to a surface, like a shady wall, rock or tree branch. In hibernation, a snail’s heart slows from about 36 beats per minute to only three or four, and oxygen use is reduced to one-fiftieth of normal.
    Snails often group together over winter. If you find one, expect many more in that protected hiding place. They burrow under loose flaps of bark, behind stacked paving slabs, around planters and pots and in gaps and holes in walls.
    “I retire within myself and there I stop. The world is nothing to me,” said the snail in Hans Christian Andersen’s tale, The Snail and the Rosebush. And with this, the snail withdrew into his house and blocked up the entrance.