|MadSci Network: Zoology|
Dear Melanie, The African Land Snail (Achatina fulica, or one of its many cousins found throughout tropical forest areas) is probably your snail as it is one of the most invasive, and introduced, snails. As well as being a splendid pet, it is also excellent to eat or as a spreader of several diseases and zoonoses (animal-to-human pathogen). Like many land snails it is prone to fall because of the shell's weight. All Pulmonate (lunged) Gastropods have habituation responses in which they fail to react to regular stimuli. The shelled species retract into their shells and either drop or use suction to hold on. Instead of losing suction, your friends could be reacting to a change in light or noise background or a vibration. Perhaps you should study to see if new recruits to your cage drop more often than the longest serving members. Most related snails seem to have a homing system that returns them to their exact shell location that they left before feeding. This too would affect whether they climb regularly to the warmth and dampness of a lid nd adjust to sleeping there. My advice would be to experiment on disorientation with a strange tank or area to see if they can settle down in a new environment within a day. If they are like garden slugs or limpets, they will find it difficult to travel in straight lines to a suitable environment area. Disorientation like this can be the death of many garden pests if they are slung onto a path area. Learning however, would be hinted at if you return them to their tank and they resume the positions in which you would normally expect them to appear. Some snails can travel 1.5 metres at least before returning to their homes every night. If you marked their shells with different coloured pens, the results would be obvious to their owners but the cause of discourteous comment from less conchophile members of the human community. The only problem with the experiment is that it doesn't prove learning has raken place. The snails, rather like the pheromonic ants, could simply be following a chemokinetic route in their slime or even more simply looking for the most favourable conditions. People have struggled for a century now to research these common habits, but learning can only be proved with associative or conditioned learning. This has been done with one or two species of water snail which remembered the information for four days before forgetting all about it!
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