I asked this very same question to a friend who is an evolutionary biologist, because where I live we do not have "snails" so I wondered if maybe these slugs that we have in abundance would be a good "survival" food. He says that while they may be "safe" to eat if cooked properly, the reason you don't already see indiginous people eating them like they do snails is that the taste is beyond horrible, and the nutritional value is not very high.