
A dusky slug dormant and fully retracted on a chilly day, in Olmsted Park.
Photo by
cottonmanifesto.
Urban species #307: Dusky slug
Arion subfuscusIt can sometimes be hard to believe that a creature very familiar to you, that you associate with your surroundings, is an alien.
Rabbits were introduced into Britain by the Romans;
dandelions were brought to North America from Europe;
pigeons were once a strictly Mediterranean species, but have become citizens of every urban place on Earth. In a similar way, today I learned that the slug that I see almost every day is originally from Europe. I already knew that the large and attractively patterned
leopard slug was introduced from the old world, brought across the Atlantic clinging to a leaf, or tumbled in a ship's hold full of soil. But I assumed that the more plain, grayish to yellowish, much smaller and more numerous slugs that are under every log I turn over, were native. These slugs, which have the common name "dusky slug" are even found at the rural wildlife sanctuary where I work--there are never leopard slugs there. As it turns out, the dusky slug's presence in North America was first detected in the early 1800s, in Boston.
Dusky slugs are quite variable in color, and produce an orange mucus that can make them look almost golden yellow. Like other slugs they are largely nocturnal, emerging from concealment at night and during wet weather. They perform lowly but important recycling duty, eating
fungi and animal feces, but will also become agricultural pests if they have the chance. They particularly favor soft plants like lettuce and strawberries.
( See them crawling on a warm wet June day. )