"It is not at all unusual to see the silvery slime trails of slugs and snails heading up walls and trees and the molluscs perching in bushes and tall herbs. This poses the chicken-and-road question: Why do they do it? I have seen one of the banded snail species two metres up a rose. You would think that the thorns would create something of an obstacle course, except that the pinpoint sensitivity and control in the snail's foot allow it to climb over a razorblade without coming into contact with the cutting edge."