Euuuurgh! I've trodden on so many snails this year, luckily in shoes, then spent TIME stamping on them to make sure they're dead.
Apparently UK slugs mainly self-fertilise and are ridiculously inbred, and now Spanish slugs are coming over taking their jobs and bringing with them diseases to which our slugs have no resistance because of their limited genepool. The Spanish slugs are also larger and breed at 4x the rate ours do. Save our slugs... if only because the other option's much worse.
Slugs are drawn by the aroma of a squashed slug as they like to feast on other slug's corpses. Apparently in some places which are heavily infested with the Spanish variety they have formed slicks on roads where one slug has been squashed by a car, four have popped down for a spot of cannibalism and in turn been squashed, sixteen have come down to eat them and so on and so forth until there's a huge olfactory beacon for the slimy little fuckers and they're drawn from miles around, all getting splatted and creating a danger to traffic.