The queen of killer slugs

A light drizzle is falling as Stine Slotsbo crouches down in front of an overgrown flowerbed, where two orange-brown killer slugs are making their way through the vegetation. Her dog, Darwin, is keeping watch. The hot, dry summer has kept slug numbers down, but now, in late August, the shift to wetter weather has given them renewed hope of reproducing. For Stine Slotsbo, the pattern has been much the same as usual: whenever a new slug season gets under way, her phone starts ringing. Journalists from Go’ morgen Danmark, Vejret, Politiken, Jyllands-Posten and Ekstra Bladet want to know more about the invasive species that has occupied the green battlegrounds of gardens across the country. Spanish slugs have, over time, become the glue – or rather, goo - that binds Danish gardeners together.

“I remember how incredibly nerve-racking it was to read the first newspaper article I appeared in 16 or 17 years ago. What if I had said something wrong? You think it’s set in stone and will be there for ever, but eventually you realise that it’s forgotten the next day. Fortunately, my head of research at the time, Hans Lykke, took me under his wing and taught me how to handle it: stick to my area of expertise and be very clear about what I know and what I don’t know. I know nothing, for example, about the feelings of killer slugs. That isn’t my field of research, so I’ll leave that to others,” says Stine Slotsbo from her garden in the village of Elev.

Know your enemy

It was her interest in ectothermic animals that originally led her to write her master’s thesis on freeze tolerance in earthworms. Then, in 2008, while working as a research assistant at the National Envi-ronmental Research Institute of Denmark, she was given the opportunity to pursue a PhD on the biology of killer slugs and the effects of climate on them. This marked the beginning of a years-long battle in the laboratory to understand the enemy – and, in doing so, find an effective way of controlling it. Knowledge that many gardeners would probably kill for. More on that later. In September 2026, Stine Slotsbo will receive the Else Kai Sass Award, named after the first female professor at Aarhus University. The award is presented to a candidate who brings knowledge from AU into wider
society and who has made a particularly positive contribution to research communication, collaboration and innovation.

“I’m very grateful, but at the same time I have slightly mixed feelings about awards. After all, this has been a joint effort involving a great many of my colleagues, and I could never have done it alone,” she says.

Two queens meet

Although Stine Slotsbo has become something of Denmark’s queen of killer slugs, there is still room for other research projects. Together with a wide range of collaborators, she has secured two major grants to investigate the potential for producing sustainable fish feed. The aim is to reduce fish producers’ dependence on conventional marine-based feed, including small crustaceans, and replace it with something as simple as worms. In a way, this takes us back to the beginning of Stine Slotsbo’s research career and her freeze-resistant earthworms. During the project, she and her colleagues discovered that the worms can themselves produce omega-3 fatty acids, which are important for fish growth and health. This means fish feed no longer needs to be enriched with fish oil, potentially simplifying production while making it more climate- and environmentally friendly. Full circle for both fish and researcher.

“It’s great fun when you actually manage to create a consortium where people genuinely work together and those competitive dynamics aren’t there. People are open, and the project itself is what matters,” says Stine Slotsbo, referring to collaborators including the Technical University of Denmark (DTU), Aalborg University and several companies.

As project leader, she even had the opportunity to present the idea of sustainable fish feed to a real queen when Queen Margrethe visited Aarhus University’s University City campus in 2023. Stine Slotsbo was given three minutes in a room with Rector Brian Bech Nielsen, The Kitchen’s Director of Enterprise Lone Ryg Olsen, and Margrethe II accompanied by her lady-in-waiting. It was a small, exclusive performance that in several ways reminded her of Forsker Fight many years earlier, when she won an internal competition to explain her PhD project in just four minutes.

“It’s a great constraint, because if you’re well prepared, you can say an incredible amount in three or four minutes. Even though meeting the Queen like that was a unique experience, what I was really thinking about was making sure everyone could understand what I was saying. And that’s always the case when I communicate my research. The only difference here was that I had to remember to address her formally rather than informally,” says Stine Slotsbo, before we have to interrupt the interview for a while and head indoors to escape the rain. Darwin barks, and the killer slugs rejoice. Because surely they have feelings?

The price of communication

There is another question that demands an answer. How much can you simplify your research before you begin to compromise its academic rigour? It is a dilemma Stine Slotsbo recognises:

“In the past, it was almost considered cheating if a researcher communicated something in everyday language, because if you didn’t use all the sophisticated terminology, you somehow weren’t as clever. It’s not that our specialist terminology is unnecessary – it’s actually really useful when I’m talking to fellow researchers. I can use exactly the right technical term without having to explain a whole host of things. But when you’re speaking to the general public, the jargon has to go, because no one becomes any wiser if people don’t understand half of what you’re saying. Fortunately, I find that young researchers have a slightly different approach to science communication from my own generation. They think it’s fun.”

The two killer slugs have now made their way indoors as well, sitting on the living-room table in a plastic container, and they appear capable of coping with all kinds of weather. At the beginning of her PhD project, Stine Slotsbo had a theory that the killer slug was not freeze-tolerant, and that this could provide the key to killing it. But the only thing that died was the idea. Since then, she has devoted a large part of her career to understanding the animal – and helping the rest of us understand it too.

The cold, hard fact is that the killer slug is here to stay.