I encourage this kind of thing in my garden:
The leopard slug or great grey slug / boasnegl (Limax maximus) is an introduced species, but unlike the spanish slug /brunsnegl almost never causes any damage in the garden despite large numbers of them…but they can eat your vegetables if your garden is too neat and tidy as their preferred food is dead and decaying vegetation! They have also, I believe, kept the dreaded spanish slug at very low numbers (they reportedly eat young spanish slugs and eggs and being highly territorial, returning to the same hiding place every morning, defend such hiding places from the spanish slug! A good guy in my opinion!!
Want to know more about what happens after the video ends? This is from Wikipedia:
“The mating habits of Limax maximus are considered unusual among slugs: the hermaphrodite slugs court, usually for hours, by circling and licking each other. After this, the slugs will climb into a tree or other high area and then, entwined together, lower themselves on a thick string of mucus, evert their white translucent mating organs (penises) from their gonopores (openings on the right side of the head), entwine these organs, and exchange sperm. Both participants will later lay hundreds of eggs”