The attack of the killer slugs!

Mark Leach is the membership marketing manager for the Society of Biology, as well as being amateur biologist in residence!

Further to my initial amateur biologist blogs, as my turn on the blogging rota approached I asked my colleague Becky if she had any ideas on where I should focus my quest for knowledge. I really wasn’t expecting the question ‘What do you know about killer slugs?’, and my response (while confirming my amateur biologist status) probably provides a better insight into my DVD watching habits than anything else.

However, as suggested I fired up Google (other web browsers are, of course available!), and discovered that my initial reaction had been way off target! Wikipedia (often a good starting point) revealed that the killer slug, more properly known as Arion vulgaris, (or the Spanish slug to its friends) is a member of the Arionidae (roundback slug) family. Having increased my slug knowledge quite significantly (if you consider ‘those nasty things that ravage our Hellebores and hate salt’ to be knowledge), I read on, to discover that the Spanish slug is a highly invasive breed.

Opinions vary on whether it did indeed originate from Spain, France or Southern England. DAISIE (Delivering Alien Invasive Species Inventories for Europe) lists it among its top 100 invasive species, and I understand it’s the only land gastropod to make the list.

My research then unearthed the SlugWatch website, which provides the discerning slug spotter with all the slug-related resources you can imagine. Their comprehensive section on our Spanish friend explains that the species was first seen in the UK in Spring 2012, and suggests that they may have entered the UK on imported salad leaves, bare root trees or potted plants. They are notable by their voracious appetite, not just limiting themselves to plants, but also tucking into dead animals, and even dog excrement (feel free to join me in a cringe!)

Typically coloured bright orange or reddish brown they breed in a similarly voracious manner, producing more than twice as many eggs as their indigenous counterparts (and it’s additionally worthy of note that they are self-fertilising!), and usurping them from our flower beds, gardens and other areas.  And it seems the situation could worsen. Just when you think you couldn’t love them any more, it appears that they produce massive amounts of mucus (ew!) which deter normal slug predators such as hedgehogs – so they have plenty of time to reach their full size of 8-15 cm, while producing copious amounts of eggs in the process. And they could even (indirectly) cause a hazard to humans as their propensity for eating roadkill has been reported to make roads slippery.

So what can we do in the face of this onslaught?  The SlugWatch website provides instructions on making your own slug traps (although rather less guidance on what to do with a boxful of slugs). They are also encouraging members of the public to report unusual slug sightings to help them to discover as much as possible about the UK slug population, and they also invite you to upload photographs.

So let’s be careful out there!