Hello Roland, Thanks for the information. As I read your post, a few questions came to mind, some more serious than others: How do you define an "occupied bottle" - does it actually have to have an octopus in it when you find it to qualify as occupied? I'm kind of confused by the terminology here, because you speak of relative numbers of shells in occupied vs. unoccupied bottles. Presumably the presence of any shells indicates that the bottle was occupied at some point? If the octopus favor brown and encrusted bottles, presumably darkness is the condition they seek? Is this therefore a shallow water species? Where did this species live before beer bottles arrived on the scene? Do they still live there? Is the species found in areas that are not littered with bottles? Are there enough "naturally occurring" (so to speak) beer bottles to support the population, or did you have to "seed" an area for the sake of the study? In your 6-month experiment, will your final examination for deterioration be based on weight loss, or just visual evidence? Could the dissolution of shells in occupied bottles be due to, or accelerated by, acids resulting from: (1) waste products of the octopus (anybody know the pH of octopus poop?) (2) carbonic acid formed from CO2 produced by the respiration of the octopus in such a small, restricted space? (3) decomposition of snail tissues not thoroughly removed from the shells by the octopus? Just a few thoughts. Don't feel obligated to answer - I'm not trying to make work for you. Regards, Paul M.