Expert is concerned Endangered sand lizards in Bonn live dangerously

Dransdorf · The sand lizard is native to Bonn. However, their population is endangered, says biologist Peter Schmidt. Why the species has to fight for survival.

 A male sand lizard. They are the most colourful lizard species in Bonn.

A male sand lizard. They are the most colourful lizard species in Bonn.

Foto: Biologische Station Bonn/Rhein-Erft

Frown, worried expression on his face. Biologist Peter Schmidt has a problem child: the sand lizard. The native species lives on the outskirts of city centres. Areas that lie fallow, offer some light grass, sand and places to retreat, warm sunny places - that's where the animals are at home. "These are areas that are often built on. People take away their habitat by building on it and tarmacking it," says Schmidt, an employee at the Bonn/Rhine-Erft Biological Station. One example is the old abattoir in Weststadt. It lay derelict for a long time, allowing lizards to nest there. When it was due to be demolished, an expert first had to look at which species had taken up residence there over the years, including sand lizards.

Schmidt is also concerned when he thinks about the potential development area between Kessenich and Dottendorf. He is certain that sand lizards also live there. "That's because there are a lot of allotments there," he says. When the railway renovates the tracks and replaces the ballast, this often means certain death for the animals. They are scared away, "or they are picked up directly with the ballast and die," says the biologist.

Humans and their building projects are not the only danger for the small animals. Kestrels and cats are too. "Cats are actually a danger to all native small animals," emphasises Schmidt. What's more, lizards are at the bottom of the food chain. The reptiles are also an important source of food for birds of prey and smooth snakes. Even robotic lawnmowers can be dangerous for sand lizards. "Real lawn mowers cause the ground to vibrate and make a lot of noise. The animals run away. Modern robotic mowers are quiet and more of a danger," says Schmidt.

Where do the lizards live in Bonn?

Schmidt would like to know where the different lizard species live in Bonn. Because there is still the common lizard and the wall lizard. However, both species are doing well. The Biological Station is calling on Bonn residents to photograph any lizards they see and report them to the Biological Station by email. "In the past, this has worked well with stag beetles, grass snakes and slow worms," says Schmidt. "Thanks to the reports from Bonn residents about grass snakes, for example, we found out that the entire Kottenforst is colonised and not just part of it," explains Schmidt. And such campaigns also help to awaken Bonn residents' interest in nature and native animals. Because he has the feeling that many people are no longer interested in wildlife. "But it seems to be slowly increasing again," he says.

There are three species of lizard in Bonn: wall lizards, sand lizards and forest lizards. The wall lizards often sit on walls or rocks. "These are places that warm up quickly," explains Schmidt. They also flit through the quarries in Oberkassel. The common lizard favours clearings in the forest and likes to sit on or between fallen trees or on tree stumps. Attentive Bonn residents can observe them with a little patience in the Kottenforst.

Schmidt is not worried about either species. The Biological Centre takes care of the animals by clearing walls or mowing areas. According to Schmidt, not much needs to be done for the common lizard. "The species is doing well thanks to the fallen trees on which they live," he says. Visitors to the Kottenforst can help protect the animals by staying on the paths.

Relocation is not the solution

When lizards are disturbed by construction projects, such as at the old abattoir, they are sometimes relocated. According to Schmidt, this is not always a good solution. This is because it is difficult to catch all the animals in a population. And the new area has to be prepared several years in advance. "Lizards are relocated too spontaneously. The new areas are usually too small and too fresh." This means that fallow land has to be created for sand lizards. This often takes two to three years. This is because the lizards need sparse grass that is around half a metre high. This only reaches the right height after a certain period of time.

Construction sites or buildings also have a different effect on the animals: they cut them up. Schmidt explains this as follows: "If the animals are isolated by a building site or a wide road, there is no longer enough genetic diversity. The animals only mate with conspecifics that live in the area. There is a risk of inbreeding." Explains Schmidt. The animals are then no longer well protected against diseases. If things go badly, an entire population can die out.

Help from the population

Allotment gardens and a diverse habitat are the best conditions the animals can find. However, deliberate cultivation only helps to a limited extent. This is because the grass in gardens is often too dense and too high, and the areas are too small for the animals. "Lizards are more likely to occur in allotment gardens because there are different conditions there. For example, sometimes a pile of old wood or stones and open ground," says the biologist. The animals prefer that. Otherwise, protecting the lizards is a matter for the city, says Schmidt. Bonn residents can help by reporting lizard finds to the Biological Station.

Call for a count

Anyone who sees a lizard in Bonn can report it to the Bonn/Rhine-Erft Biological Station. Bonn residents and residents of the Rhine-Erft district should report the animals by e-mail. There is a reporting form on the Biological Station's website. The place and time of the sighting and additional information such as the colouring, size of the lizard and special features of the animal are requested. You can also upload a photo. The Biological Station will get back to you after the report. The animals can also be reported using the Obsidentify smartphone app. The animals are automatically identified based on the photo. The data is retrieved regularly.

Original text: Maike Velden

Translation: Mareike Graepel