Question: I have found several of these large black slugs in my garden. I haven’t come across them before. Can you tell me what they are? I was also wondering if they are native or introduced and whether they are likely to cause much damage in my garden. Answer: Thank-you for sending your slug to the Discovery Centre at Melbourne Museum. We sent it to our invertebrate department and they have identified it as the species Arion ater (commonly known as the Black Slug). Black Slugs are large land slugs; a fully-extended adult can be 15 cm long. They have a dark brown to black body, occasionally mottled to variegated with rows of prominent tubercules. Their foot is fringed with black and orange or yellow stripes. Black Slugs cover themselves in thick, sticky mucus which serves to keep them moist and protect them from predators (it apparently tastes quite foul). This mucus can be quite difficult to remove from our skin. Black Slugs are native to Europe. They are considered not to be good world travellers and, until recently, their presence in Australia has only been recorded in a few localities. The Melbourne Museum Discovery Centre first received a request to identify a Black Slug in 2001 and we have only received one or two enquiries about this species each year since then. Black Slugs are still not considered to be established in Australia. However, from what we’ve learned from the members of the public who have sent them in, there is a population of these slugs in the Dandenongs (one enquirer reported that he had collected 4000 Black Slugs on his Dandenong property).
In 2005, we received a specimen from the Otway Ranges (this was the museum’s first record of Arion ater from this area). Records from other museums show that the species is also present in parts of New South Wales and South Australia. So far at least, they seem to be restricted to gardens and similar cultivated habitats. Black Slugs are regarded as garden pests in Britain and Europe. They can cause damage to seedlings in spring, but their preferred diet consists of rotting vegetation, fungi, manure and even dead animals. Despite their unpleasant-tasting mucus, Black Slugs do have some natural predators. These include hedgehogs, badgers, shrews and moles. None of these species occur in Australia.
Thanks for your query about slug eggs. We've sent this to one of our experts and will get back to you with an answer as soon as possible.
Sounds serious, Carol. We'll get back to you as soon as we've heard back from the relevant Collection Manager.
Okay, Carol. We've been in touch with staff in both our Live Exhibits and Invertebrates areas who have come back with their advice. Regarding the eggs, it's likely that the salt-water solution will have been sufficient to rupture the walls of the eggs and kill them effectively. Ammonia would be another effective solution. As for the outbreak, our records suggest that populations of Arion ater seem to occur between November and March, usually following periods of wet weather. As recently as 2007, the species was reported as "no longer in Australia," despite isolated pockets in the Dandenongs and Otways that provide suitable conditions for them to establish breeding populations. It's because they are not widely recognised as "established" in Australia that there is such a dearth of literature on their potential distribution and their effect on native fauna and flora.
Thanks for this information, Abigail. We've passed it on to staff in the Museum. Unfortunately we cannot offer advice about controlling the pest. You may consider contacting a professional pest-controller about the problem. The Department of Sustainability and Environment would be the people to contact about any collective response to the outbreak; we're sure they would appreciate localised reports such as these.
We love receiving comments, but can’t always respond.
We really need to see an image or examine a specimen to be sure.
It sounds like it could possibly be Arion ater, (a large & black slug introducer from Europe) however we really need to examine the specimen in order to provide an accurate identification.
Based on the few records that we have, population explosions of Arion ater seems to occur from around November - March, usually following periods of wet weather.
It is interesting that as recently as 2007, Arion ater was reported as “no longer occurring in Australia”, however contrary to this report, it seems that a few isolated pockets in the Dandenongs & Otways provide suitable conditions to for them to be able to establish breeding populations.
Since they are largely not regarded as being established, there is a dearth of literature available on their potential distribution or their effect on native fauna & flora.
Unfortunately, Museum Victoria is not qualified to provide advice on how best to eradicate slugs.
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