I struggled with slugs in my garden this Winter. I live in a mild weather location, an island in the middle of the North Atlantic Ocean. Our Winters are chilly but not cold. We have no snow, but we have a lot of rain and wind, and with that rain comes a lot of snails and slugs.

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Two-Toned Gulella (Huttonella bicolor) is a predatory snail introduced around the world.

In my readings on snails and slugs, and ways to eradicate them, I came across the predatory gastropods. I had known that there were a large number of these in the ocean (from my time scuba diving), and I recalled at least one in the Pacific Northwest. However, I was unaware that there are in fact a number of terestrial predatory gastropods… land-living, carnivorous snails and slugs. Cool!

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Gray Lancetooth Snails (Haplotrema concavum)

Here are a few quick facts:

  • Most predatory gastropods live in the ocean
  • The terestrial predatory gastropods will eat other snails and slugs if given the choice, but if none are available, they will eat plants.
  • Predatory slugs and snails may eat their victims whole. If the victim is too large, then the predator will eat as much as it can and leave the rest hanging out of its mouth until the first part is digested. This can sometimes lead to a slug or earthworm being digested from it bottom up and still being alive to watch and feel it!
  • Predatory slugs and snails may just take “bites” out of their victims. This is accomplished with rows of teeth (radula toothlets) that rasp away at the victim… kind of like a file being slid across soft wood.
  • Snails will often pull themselves into their shells to hide from the predators. This may save some snails, but a few predators can get past this defense. Some predators will cut a hole in the shell which breaks the vacuum and allow the snail to be pulled out. One predatory gastropod can even excrete acid to burn its way into the shell!
  • There are a number of terestrial predatory gastropods in the world, and there is a good chance you have a native one near you.
  • It is best to encourage native predatory gastropods by learning to identify them and giving them a free pass in the garden, even if they do eat some of the plants.
  • I see no problem with relocating native predatory gastropods from one location to another as long as they are in their native range… i.e. you come across some in the woods near your home and you carry them back to your garden.
  • There is a BIG problem with relocating non-native predatory gastropods… e.g. the Florida Rosy Wolfsnail was relocated to Hawaii, on purpose, in an attempt to eradicate the Giant African Snail that had become invasive in Hawaii. The Florida Rosy Wolfsnail has decimated the natural Hawaiian snail population and has not touched the Giant African Snail population
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Rosy Wolf Snail (Euglandina rosea) about to eat a slug.

Here is a quick rundown of some of the more well-known predatory gastropods:

  • Rosy Wolf Snail (Euglandina rosea, Family Spiraxidae): In the United States, it is found in Alabama, Florida, Georgia, Hawaii, Louisiana, Mississippi, South Carolina and southeastern Texas. It is widespread, but usually found singly in hardwood forests, roadsides and urban gardens.
  • Decollate Snail (Rumina decollata, Family Subulinidae): Native to the Mediterranean area, but introduced widely in the United States, Bermuda and Mexico. It is widespread, but localized, in the Sun Belt from California east to Florida and north along the Atlantic coast to Pennsylvania. (Top Photo: a bunch of Decollate Snails attacking a Brown Garden Snail)
  • Gray Lancetooth (Haplotrema concavum, Family Haplotrematidae): Southern Canada to the Gulf States and west to eastern Nebraska and Oklahoma.
  • Two-Toned Gulella (Huttonella bicolor, Family Streptaxidae): Introduced from Asia or southern Africa. Widespread in the Caribbean region. In the United States, it is found in Florida, Louisiana, Mississippi, South Carolina, and Texas. It is also found in Brazil, Nicaragua, Australia (Northern Territory), and the Pacific area.
  • Unnamed Predatory Snail (Varicella gracillima floridana, Family Oleacinidae): Found only in the southern tip of Florida.
  • Predatory Glass Snail (Daudebardia species, Family Oxychilidae): Found in central and southern Europe.
  • Dalmation Predator (Poiretia cornea, Family Spiraxidae): Found in western Europe to eastern Asia (related to the Rosy Wolf Snail above).
  • Worm-Eating Slugs (Testacella species, Family Testacellidae): Found in Europe, Africa,  Britain, and Islands in the North Atlantic. These slugs with a shell (yeah, they are still called slugs, not snails) primarily eat earthworms and live most their lives underground. There are some reports of these slugs eating insect larvae as well.
  • Ghost Slug (Selenochlamys ysbryda, Family Trigonochlamydidae): Found in the UK and Europe down to Turkey. Also a earthworm eater.
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Ghost Slug (Selenochlamys ysbryda)

 

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Photo References:

  • http://farm4.staticflickr.com/3587/3590414352_08d80e1cdc_o.jpg
  • http://www.associatesinsectary.com/resources/2/decollates-snail.jpg
  • http://www.jacksonvilleshells.org/70582.jpg
  • http://entnemdept.ufl.edu/creatures/misc/gastro/snail_eating_snails08.jpg
  • http://upload.wikimedia.org/wikipedia/commons/c/cc/Ghost_Slug_adult.jpg