Tiger in the garden

After a night of heavy rain a corner of our lawn transformed to a biotope. It is where I detected this impressive specimen of a 'tiger slug'. That's what we call it around here, although I have seen that in proper English the name is 'leopard slug'. Anyway, they have an image problem, supposed to be a dangerous predator in the house garden. The bigger it appears, the bigger must be the appetite to eat all the green around.

Seems that it's all wrong and leopard slugs are considered to be beneficial and should be protected in garden areas. Mainly feeding on withered plants, and even better, feeding on the 'bad' slugs and their eggs. Even more exotic: their alien like mating behavior documented in this BBC clip.