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Giant Garden Slug

Limax maximus

Identifying Characteristics

  • maximum length 10-20 cm
  • pale-grey, ash-coloured, brownish or yellowish-white
  • body streaked or spotted with black markings that sometimes merge to form lateral bands
  • pneumostome (large pore through which the slug breathes) positioned in rear portion of mantle shield on right side of body
  • pale foot fringe with 48 rows of blackish tubercles
This is a photograph of a Giant Garden Slug on a leaf. 4 images
This is a map of British Columbia showing the spread of invasive species.

Watch it

This is a still from a video on slugs showing a Giant Garden Slug in a dish with a carrot.
(Video 2:00 3.81 MB)

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Video transcript

Slugs
Melissa Frey, Curator, Invertebrates, Royal BC Museum

My name is Melissa Frey, Curator of Invertebrates at the Royal BC Museum.

This is a still from a video on slugs showing a Giant Garden Slug in a dish with a carrot.

You identify a Giant Garden Slug typically by it’s size for one thing, they are large, they can measure somewhere between 10 and 20 centimeters. Although these individuals are a little bit smaller.

In terms of their colouration, their colouration can vary, but they tend to be brown to grey in colour.

This is a still from a video on slugs showing a Giant Garden Slug in a dish with a carrot, one of the slugs is trying to escape.

They’re mottled with these black to dark brown spots all the way along their body.  

They have a region called the mantle, which is up here near the head, and this mantle has little tiny concentric ridges or folds which, if you look closely enough you can see those.  This is characteristic of this species relative to something like the native Pacific Banana Slug because the Pacific Banana Slug has on the mantle, little tiny granules.  

The other thing about the Garden Slug here is that you can see here on the right side of the mantle, it is an opening. This opening is called the pneumostome, and the pneumostome is what they use to breath out of. The location of this pneumostome is slightly behind the midline of the mantle posterior. So that is another characteristic that you can use to key out the Garden Slug.  

The Giant Garden Slug, like many terrestrial snails and slugs that have been introduce to BC are typically considered pests. We don’t always know exactly how they interact with native snails and slugs but one of the trends that we tend to see is that in regions that these species are introduced we tend to see a decline in the native snails and slugs in that area. 

Report a Sighting

An alien visitor in your garden.

The Giant Garden Slug goes by a few names, including the Great Grey Slug and the Leopard Slug. It is a common garden companion that generally feeds on fungi and rotting vegetation, but might also snack on other slugs or snails.

This species of slug is one of the largest of its kind and lives three to four years. These slugs hide during the day and are active at night, but always stay close to home.

Impact on Communities and Native Species

The Giant Garden Slug though not a garden pest, may out-compete or prey upon native slugs or snails.

This species of slug is native to Europe and Asia but has spread around the world and to most of southern British Columbia, including the Greater Vancouver region, the Fraser Valley, the Okanagan, the Kootenays, the Cariboo, southern Vancouver Island and the Gulf Islands.

Invasion History

The Giant Garden Slug likely arrived in British Columbia through passive dispersal, perhaps hidden in pots of imported plant or as eggs mixed with soil. This is also how the species moves around the province, helped by humans in garden refuse or with wood, rocks, soil or other materials that are transported to a new location.

This species of slug is native to Europe and Asia but has spread around the world and to most of southern British Columbia, including the Greater Vancouver region, the Fraser Valley, the Okanagan, the Kootenays, the Cariboo, southern Vancouver Island and the Gulf Islands.