Strange snakes can often be seen in damp areas of the city, such as the Britzer Garden. They look like a house snake – like them, they have two bright crescent-shaped spots behind their heads. But unlike the long-established ones in Berlin, they do not have a simple gray back. Instead, two light stripes run across the body.
A Berlin research team has now assessed more than 400 sightings of snakes in the city that nature lovers have made using identification apps such as iNaturalist.
The rare specimens are actually snakes, explain researchers from the Berlin Natural History Museum. The bright markings on the back come from a subspecies native to the Balkan Peninsula and Turkey: the Balkan snake (Natrix natrix moreotica).
Over the past three to four decades, these animals have interbred with local populations, which have since carried genetic parts of the southern snake. Berlin has long been an important transit point for terrarium animals in Europe. To this day, hobbyists keep reptiles at home. This has left its mark on local wildlife.
Striped snakes have appeared in seven locations across the city, according to the journal Conservation Genetics. Among others, in the Tegeler Flies, in the Spandauer Forest, in the Britzer Garten and in the Spreepark in Treptow. Almost all British snakes are striped.
Study author Frederick Griesbaum sees no evidence that the snakes arrived in Berlin hidden by building materials or rubble. “The responsible owners have probably abandoned the animals,” he tells the Tagespiegel newspaper in several places in the city.
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Until the 1980s, getting a stylish striped snake was easy. Many vacationers brought a snake with them from Croatia or Albania, which is now strictly prohibited. The animal could also be purchased in Berlin pet stores for 20 marks.
Concerns about local snakes
Snakes are harmless to humans and there is no need to be afraid of them, says the scientist: “Even if you catch a snake, you don’t have to worry about being bitten.” Animals tend to defend themselves by spraying smelly secretions.
He experienced this first-hand when he and his colleagues collected 27 snakes for a study to analyze their genome. Fishing is prohibited without permission from the authorities.
It turned out that another subspecies from Hungary, Austria and the Czech Republic crossed with local snakes. Their scales are reddish and have no stripes. It migrates from these regions and is increasingly found in southern Germany.
The researchers have “reason for concern” because mixing of gene pools is undesirable from a conservation perspective, they write in their essay. When subspecies are crossed, species diversity suffers. The animals may also have a survival disadvantage: the lighter Balkan snakes are adapted to warmer climates and different flora and fauna.
The Berlin snake (Natrix natrix natrix) is typically light to dark gray in color and without stripes. Characteristic are yellow spots behind the head.
© imago/blickwinkel/M. Kun
Contain the spread
In theory, the spread should be contained, the researchers write. However, in practice, catching snakes is very difficult, Griesbaum said in an interview. Since there is no immediate threat to local wildlife, he advises waiting. It is possible that the stripes will disappear again in a few generations. However, populations should continue to be monitored.
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Berliners can help by using apps like iNaturalist or Species Finder from the Berlin Conservation Foundation. If you want to observe shy snakes, you should visit the ponds in the protected biotopes of the city. Gadi are excellent swimmers and feed mainly on fish and frogs.