I didn't realise that it was a touch sensors, and was wondering through the article how on earth a slug was pushing the buttons to bell people, and maybe somehow its slime was conductive enough to get inside and short things?
if you look on the top of its head its got two arm like appendages that it can touch things with, probably did it with those
Those are its eye stalks. I don't imagine pressing with a lot of force on its eyestalks is something a slug likes to do, but then again I haven't asked any yet.
it was ringing the bell somehow, what else could it have been? even a particularly fat slug would have trouble pressing the bell as its vertically aligned.