By Lily Moffatt, Assistant Producer
Incredibly, the UK is home to the largest land slug in the world – the ash-black slug.
Despite its name, they come in all different colours, from toffee-blonde to brown and deep charcoal. Juveniles are usually lighter in colour. These formidable beasts (or gentle slime souls) are found in ancient woodlands, where they feed on fungi, lichens and algae.
On moist summer nights, these creatures become aroused, searching for a mate with whom they will undertake one of the most intricate and elaborate mating rituals in the animal kingdom. As a crew, we were aware of the mating behaviour that we wanted to capture, yet getting the slugs into prime position to ‘do it’ wasn’t so simple.
The mating ritual of the ash-black slug has to be seen to be believed…
Filming this required patience, persistence and a little help from our friend John Walters. John had witnessed this behaviour in the wild on several occasions, so he had a pretty good idea of when and where it might happen.
Our crew were briefed on how to make the slugs feel at home and comfortable so that we had the very best chance to capture the performance. It required the perfect overhanging, moss-covered branch, that was kept moist with natural rainwater, a full moon to set the scene and many, many hours of waiting during the middle of the night.
If we were going to have a shot at filming it, we’d only get it once – so we had to be on our guard, primed and ready to roll when the slugs changed tactics.
Fortunately, we had with us wildlife cameraman Alastair MacEwen – one of the most experienced camera operators in the wildlife filmmaking industry and a seasoned pro, especially when it comes to macro filming. Alastair has a gift – for one, I have never met anyone more patient and dedicated, as Alastair. His ability to set the scene with cameras, to create a wild studio, all the while lighting it in darkness, is something to behold when on location!
The ‘green room’ was created so that we could pair up numerous slugs and watch how their behaviour towards one another unfolded. What we were on the lookout for was incessant following by each slug. This would be a very good sign that mating would soon be on the cards.
The words, “we’ve got a follower” were music to my ears as the clock struck 1am. This could be it. Placed carefully on the branch (which was methodically sodden from John’s sprayer), the slugs still seemed enticed by each other, so we watched on.
What slowly unfolded in front of us was quite simply, beautiful.
Intertwining together, the two slugs locked into a tight corkscrew formation. As they did so, their excess slime formed a bond, allowing them to dangle down like trapeze acrobats.
For the final act, it gets wilder still. From behind their large mantles (a section of their body right behind their head), two penises emerged, almost acting independently, they immediately bonded and wrapped around each other. This is when fertilisation occurs between the two hermaphrodite slugs. The penises that are interlocked fan out, and laterally flatten to increase their surface area. They turn from a light bluish-hue to an angelic translucent white, and with the moonlight dancing off the scene, they became magical pendulums of love.
Awestricken is the only word to describe how we felt behind the lens when watching this mating ritual play out in front of us. I’ve been lucky enough to witness some incredible species and behaviours in the natural world, but this is easily in my top 5 of the very best!
You’ll either love it or hate it, but try and relish in the beauty of one of the most elaborate displays of love in the natural world, by the biggest land slug found in our ancient woodlands.