In answers to What kind of hot pink eggs are these? and the linked duplicate I found out that snails that live in the water will climb up a smooth stick or branch to deposit their eggs. Today I saw several large (8 to 10 cm) snails climbing trees both a relatively smooth one and one with considerably rough bark.
How do these large and heavy snails manage to adhere safely to the sides of trees and climb so high? Is it adhesion? Is suction involved?
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above: June, northern Taiwan lowlands in a damp area. They look similar to the species discussed in answers to What are these four large snails doing? below: from What kind of hot pink eggs are these?