Actually, an interesting point is that those guys were never placed there by humans, rather one day, they decided to invade boat decks in Piper 39, and stayed there ever since (See http://www.cbsnews.com/stories/2009/11/24/eveningnews/main5764873.shtml). Crowd loved them, and soon they were a major attraction, which allows those snaky invaders to stay there unmolested
