Hungry Slugs Can Inhibit Grassland Biodiversity by Eating Too Many Seedlings

Selective grazing by garden slugs may be inhibiting grassland biodiversity by preventing key species from becoming established in the UK's hay meadows, according to research from New Castle University.

The large-scale impact that grazing slugs may have on grassland conservation projects is not well understood, but for the first time, researchers have shown that the presence grazing slugs may reduce the presence of certain plant species.

"We know a lot about the benefits -- and drawbacks -- of grazing by larger vertebrates such as cows and sheep but we haven't studied in detail the impact slugs might have, particularly on very young plants in meadows that we are trying to restore," said Sara Barlow, who carried out the research while employed at New Castle University.

The slug in question is Deroceras reticulatum -- otherwise known as the field slug, and Barlow's research suggests that in order to establish and conserve key grasses and plants, species management of the field slug would be helpful.

"What these initial studies have shown is that Deroceras reticulatum may actually be very damaging in this situation due to it finding some key species particularly tasty," Barlow said.

One key species, red clover, is "particularly important due to the symbiotic bacteria which live in its roots and help to fix nitrogen into the soil, benefitting not just the clover but all the meadow seedlings."

One reason why slugs can have such a great impact on grasslands is because they prefer to eat seedlings rather than grown plants. Among the grasses and wildflowers in the meadow where the researchers worked, the slugs had clear dining preferences.

"Just like us, slugs have their favorites and will eat some plants in preference to others," said Newcastle University's Gordon Port, a senior lecturer and an expert in pest management.

"We have to cope with native slugs in our gardens and crops, but this research shows they can be equally damaging in natural systems. If invasive species, like the Spanish slug establish in the UK it will move the battle against slugs to a much higher level."

Barlow and her colleagues' work is published in the Annals of Botany.