Aesculapian snakes in Bratislava: from observations to scientific research
A research team from the Faculty of Natural Sciences of Comenius University Bratislava (CU) has examined how the Aesculapian snake (Zamenis longissimus) has adapted to urban life. Their Bratislava-focused study was published in the highly regarded international journal BMC Ecology and Evolution. The project also actively involved the public. The effectiveness of this approach is reflected in nearly 600 verified observations collected over four years, providing insight into how this protected snake species has adjusted to city conditions.
Zoologists from the Faculty of Natural Sciences of CU mapped the occurrence of the Aesculapian snake across Bratislava. Their research on Slovakia’s largest and most endangered snake was supported by public participation via social media. Based on processed observations gathered through citizen science, the team published their findings in BMC Ecology and Evolution.
Methodology and data collection challenges
The researchers created a dedicated Facebook page to collect data, restricting observations to the cadastral area of Bratislava. “The first and essential requirement was a photograph of the snake, followed by the most precise possible coordinates of the sighting—when and where it was seen, the type of environment, and its behaviour,” explains Petr Papežík, one of the study’s authors. Not all observations were complete, but most records were usable and included in the study.
Public data collection took place between 2019 and 2022. The team gathered approximately 600 observations of Aesculapian snakes and 200 of other snake species. Processing the data was resource-intensive: “At peak activity, we received 12–16 observations per day, and each took 15–20 minutes to process, ultimately requiring the capacity of two people.” After the study was published, the Facebook page was placed in hibernation and now serves primarily as an online advisory platform for snake identification across Slovakia.
Thanks to cooperation with Bratislava residents, zoologists from FNS compiled the data into a final scientific output—a study published in December in a leading journal. “The study provides the most detailed overview to date of this species’ ecology in an urban environment and shows that citizen science can be an effective tool for monitoring reptiles in large cities,” confirms Petr Papežík. He believes the project’s success lies in public engagement, which helped create a unique dataset. Beyond mapping distribution, it also raises awareness of reptile conservation in urban settings.
Key findings on the Aesculapian snake
The species favours a mosaic of open woodland, less intensively used structures, and gardens, while avoiding agricultural land. Its daily activity peaks in spring and early summer, mainly around midday and in the afternoon. “It is a species that does not avoid humans, remains faithful to its territory, and occupies relatively small areas. It often lives close to people: in sheds, compost heaps, gardens, garages, or around houses. It typically retreats into tight shelters where it can feel secure from all sides, emerging mainly to feed or, in spring, to mate. Even the ancient Slavs revered the ‘housekeeper snake’ as it eliminated rodents and helped protect households from disease - something it effectively still does today,” says Papežík.
Spatial distribution in Bratislava
The data indicate that the Aesculapian snake is relatively common in Bratislava, occurring mainly in the Little Carpathians and along the Danube. The city is distinctive in its close connection to natural environments. “If you park near the Lanfranconi bridge, within 15 minutes you can reach the Pečňa Forest on the Petržalka side near the Austrian border, where the species lives in a natural habitat. You may also encounter it at Železná studnička or near Devín Castle. In the Botanical Garden of Comenius University, you can observe not only the Aesculapian snake but all four snake species found in Bratislava - the grass snake, dice snake, and smooth snake,” notes Papežík. The analysis also shows that the species uses a diverse mosaic of urban and natural habitats, while being less common in the highly urbanised city centre, suggesting ecological differences between the Bratislava population and those at the northern edge of its range.
As part of the project, the zoologists also organised several field excursions. Participants included reptile enthusiasts as well as families with children, who learned both how to identify snakes and how to behave around them.
Recommendations for protection and the public
“As the species is protected, the basic rule is not to kill it and ideally not to handle it; any handling requires a permit,” advises Papežík. The Aesculapian snake can grow quite large, with males reaching 1.5 to 2 metres in length. It feeds mainly on rodents and birds. It poses no danger to humans; its bite is harmless and comparable to a few pinpricks. “If necessary, thick winter gloves are sufficient to handle it and move it outside carefully, but handling should be kept to a minimum to avoid injury to the animal. Alternatively, the police or fire brigade can be called for assistance,” he adds.
P. P. archive photos