The toothless dormouse snails move

Recently, snail expert Jörg Rüetschi, together with rangers from the Zurich Wilderness Park, began relocating the toothless slug (lat. Balea perversa) from the Wilderness Park to the Schnabelburg (see box). "The effort involved in the relocation is greater than expected," says Rüetschi. The snails are specialists in playing hide-and-seek: Often only the tiny tip of the snail protrudes from a hole that is barely larger than the diameter of the shell. This is only one millimeter. The mini snail is also hardly distinguishable from the rest of the tree in terms of color. The search is therefore a great challenge even for experts. Nevertheless, the more trained the eye, the quicker the success. The weather conditions are also crucial for the rescue operation: "The ideal conditions are high humidity, drizzle and sufficient bright light," explains Jörg Rüetschi. Otherwise the snails retreat too far under the bark. The old chestnut trees, on which a large population of toothless slugs was found, once formed a shady avenue. The trees had to be felled for safety reasons.

Uncomplicated bark dwellers

Toothless slugs need little to become at home in a location. They feel at home on all trees with rough, torn bark. They prefer to live on old, moss-covered trees. Small cracks in which a minimal amount of residual moisture remains even during longer dry periods are important for the survival of the mini-snails. It's not just trees that are suitable: slugs also find ideal living conditions on old walls with crevices to hide in.

Will the reintroduction succeed?

The snails' new home is in the Sihlwald forest on the ridge between the Hochwacht and the Schnabelburg. There, the mini-snails are freed from their moving boxes with tweezers and released onto sycamore and ash trees - "anointed", as the technical term goes. Twenty toothless slugs are to provide offspring on each of the old trees with their rough bark. Both the trees and the snails have been marked with a colored dot. Jörg Rüetschi will search the sites again in a year's time at the earliest and hopes to find as many of the marked snails as possible and thus ensure a successful reintroduction.

The Schnabelburg - a well-known home for the slipper snail

The area around Schnabelburg Castle on the Albis mountain range is not a new habitat for the toothless slipper snail: the population of the toothless slipper snail was severely decimated by the renovation of the castle ruins, which were in danger of collapsing, in summer 2011. The archaeologists plastered the walls so thickly that the habitat of the small snail was destroyed. They only left a few small sections of wall untouched, as the Tagesanzeiger newspaper wrote at the time. Even the artificial cracks that were made in the new plaster in further renovation stages did not lead to the hoped-for success. The snail population has not recovered.

Go on a search!

The toothless slug is on the Red List of endangered species. Toothless slugs can only be found in very few locations in the canton of Zurich. However, as only a few experts know and search for the animal, more locations are possible. Look for old trees with rough, torn bark in the park, garden or forest. Found it but not sure if it really is the toothless slug? Take a photo of the snail so that the mouth is clearly visible. Send the picture with details of where you found it to the snail expert Jörg Rüetschi(joergrueetschi@gmail.com).

An adult toothless mouth snail is only about ten millimetres long and one millimetre wide. This makes it somewhat smaller than the other mouth snails. Its name says it all: it is the only one without "teeth" or "lamellae" among the various, sometimes frequently occurring mouth snails. This means that there are no special structures such as wrinkles or calcium deposits in the mouth of the shell. With the help of a magnifying glass, it is therefore easy for trained eyes to recognize. However, with a little flair and ambition, even interested amateurs can quickly recognize the snails.

Further information

Bianca Guggenheim
Communications, Zurich Wilderness Park Foundation
Tel. 044 722 55 22
bianca.guggenheim@wildnispark.ch