It is very common to find these snails (formerly Achatina fulica, not sure if the revision is widely accepted) behind trees. Or on trees, or on the street, or under a table, or on a wall, or simply everywhere. But finding them in 2nd place as worst alien on our planet, behind a tree, that was a surprise. So how could a snail take over the world? They originate from East Africa. And at least a few times they were brought in on purpose, on nutritional purpose to be more exact. Sure, it’s like a large, easy to bread land clam, what’s the difference? The difference for sure was, and is, people don’t like it! They for example don´t like the dark color of the flesh. Modern cuisine ideas? Please note the warnings about parasites in the snails. After a rain, these snails will be everywhere, and on sidewalks they are under constant risk of death by trample.