Alien animals can destroy the ecosystem

An American red-eared terrapin (red-eared slider / Rotwangen-Schmuckschildkröte) was spotted in the Choller area and in the Steinhausen Waldweiher. This alien animal is a threat to the native amphibian species. Simply releasing pets into the wild is, in fact, illegal, and often has unpredictable consequences for the native flora and fauna.

Pictures of sunbathing turtles in the Steinhauser Waldweiher are repeatedly sent to our newspaper, and numerous reports of sightings are also received by Stefan Rey, project manager for Species Protection and Databases at the Zug Office for Space and Transport (Amt für Raum und Verkehr). "However, you do have to be able to distinguish between the foreign, American red-eared terrapin, and the native European terrapin, which is under threat and is being protected from extinction. This animal also occurs sporadically in our region," emphasizes Stefan Rey. The two are easy to distinguish from each other. "The American species has white-yellow stripes and a typical red spot behind the eyes. The terrapin, on the other hand, has yellow spots."

In the 70s and 80s, the terrapins were considered to be uncomplicated pets, and they were often purchased without knowing much about them. "They can reach a size of 30 centimetres, however, and an age of up to 40 years," explains Niklaus Peyer from the Coordination Office for Amphibian and Reptile Protection Switzerland (Karch), Regional Representation of the Canton of Zug. When people had had enough of their pets, they would often simply release them into nature. "This is illegal, punishable and very dangerous for the local amphibians."

Diseases introduced with catastrophic consequences
Red-eared terrapins belong to the class of alien animals, the so-called ‘neozoa’. They often manage to survive in the wild, and, on the one hand, can spread diseases, while eating the spawn of native amphibians and insect larvae on the other, among other things. "Introduced diseases can have devastating consequences and can decimate native species within a short time," notes Niklaus Peyer. The two experts recall the crayfish plague (Krebspest) that was introduced 20 years ago by an American crab, and that practically eradicated the European crayfish that were native here.

Photo 1: The European terrapin can be found sporadically in the Zug region. It can be recognized by the typical yellow speckles.                                               Pascal Halder/PD
Photo 2: This is also a native animal, a typically black-speckled grass snake, as has already been spotted in the Choller area in Zug. It is completely harmless and can be found near the water.                                                                                                           Image: Niklaus Peyer/PD

The trade in red-eared terrapins is prohibited in Switzerland in the meantime. Where possible, any animals that are sighted are captured and taken to reception stations, animal shelters or zoos. "We have only been able to detect reproduction in the wild in isolated cases in Ticino, among other areas," says Peyer. However, as the terrapins have a very long life expectancy and the climate is changing in their favour, it is possible that this may change in the future.

"If they reproduce, we’ll have a huge problem."

Because what can be done against it? "There’s only the unpleasant possibility of using poison, which will also kill other animals, or to introduce predators, which in turn can have unforeseen consequences for the ecosystem of the water," explains  Niklaus Peyer. As a further measure, ponds would occasionally be emptied and animals captured. "The variety of alien fish species that you can find is unbelievable, from goldfish to sunfish."

"These processes are usually irreversible," adds Stefan Rey. It has not even been possible to eradicate the American crabs. That’s why the cantonal authorities repeatedly carry out educational work and appeal to the population not to release pets into the wild under any circumstances. "People are often not aware of the chain reactions they are setting in motion. It's very important that they understand this." It's definitely not an act of animal love to give pets their "freedom".

Animals travel by train
Foreign animals not only spread through being released into the wild. They sometimes also travel on trains, planes or ships as stowaways. "We notice that wall lizards (Mauereidechsen) have spread strongly along the railway transit routes," says Peyer. They like to stay on the sunlit stone walls of the stations, can hide into waiting freight trains and sometimes travel long distances with them. Another example is mussels, which adhere to hulls of ships and are transported with them to other waters. "If you’re planning to move your boat, it is absolutely necessary to clean it thoroughly before transport."

"Numerous insect species enter Switzerland with fruit and vegetable imports from all kinds of continents."

Some eggs or larvae, such as those of the dreaded Asian long-horned beetle (Laubholzkäfer), hide in pallet frames and are brought into the country in this way. These consequences of globalisation can hardly be controlled any more, nor can the damage that has already been caused be reversed.

Networking protected areas
A lot is being done in Switzerland to preserve the native flora and fauna, and the cantons are working together to network the various nature reserves. explains Stefan Rey:

"It's about creating an ecological infrastructure to give animals and plants the opportunity to colonise new areas."

Contrary to popular belief, it’s not a case of simply re-settling amphibians and reptiles in locations where their species have been expelled or displaced. "If the animals come from a different area, they may also have a different genetic disposition."

“Stepping stone” biotopes are therefore made available, and attempts are made to network these in such a way that the animals themselves can migrate safely and repopulate the areas. The pond in the Steinhauser Forest is an amphibian spawning areas of national importance. With the connection to Zurich areas and the Reuss Valley, an important networking axis is created. "The natural colonisation of the areas also enables intermixing, which prevents the genetic impoverishment of the populations, i.e. inbreeding." This process requires a lot of time and patience, however, and suitable areas, of course.

Rare encounters of the somewhat eerie kind
"We often get calls from people who are horrified to report an encounter with a snake," says Stefan Rey. In addition to the blind lizard, which belongs to the family of lizards, but is often thought to be a snake, two real snake species are native to the Zug region. "The grass snake (Ringelnatter) can be found near the water. It is typically grey in colour and has black speckles." This excellent swimmer can reach a length of up to 140 centimetres, and is occasionally encountered while bathing in Lake Zug.

The smooth snake (Schlingnatter), which has a maximum length of only 75 centimetres, prefers dry areas. It can be grey or brown, and also has black speckles. Both snake species are very shy, completely harmless and non-poisonous. Anyone seeing them should remain calm and enjoy this rare sight.

A year ago, an Aesculapian snake, a snake native to Ticino, was spotted in the Seeliken Badi in Zug, and was even filmed. "We were able to capture it some time later," reports Niklaus Peyer. The experts can only speculate how it got to Zug. As its exact place of origin was not known and it was not known whether it had lived in freedom at all, a resettlement was out of the question. "That's unpleasant for us. We then only have the option of killing such an animal or housing it in a reception centre." The snake was lucky, however, as Niklaus Peier gave it a new home in a private terrarium.

Further information is available at: www.umwelt-zentralschweiz.ch and www.zg.ch/reptilien

Foreign plants are also dangerous
Human beings are almost always involved when it comes to the settlement of alien organisms. This also applies in the plant world. "The Confederation and the cantons spend large sums every year on combating invasive, alien plants, so-called neophytes," reports Stefan Rey, project manager for Species Protection and Databases at the Zug Office for Space and Transport. The best-known examples of this are the goldenrod and the cherry laurel. "It is incomprehensible that while we are actively fighting the plants, they are still being offered in some garden centres. The legislation is clearly lagging behind here." The expert strongly advises people to seek advice from a horticultural company that specialises in native plants.