Hamster (Cricetus cricetus) and ground squirrel (Spermophilus citellus) in the metropolitan area of Vienna, Austria: Urban development vs. species protection

Although European hamsters and European ground squirrels are listed as critically endangered on the IUCN Red List of Threatened Species , their habitats are becoming increasingly smaller due to the rapid expansion of the city of Vienna. The distribution of both species over the period 2000–2023 was documented by compiling a map based on georeferenced data from scientific monitoring and citizen science collections. Based on this, the population sizes in the metropolitan area of Vienna were estimated at 4000 hamsters and 16000 ground squirrels. An overview map was also created for each of the two species, which contains the names of the most important local occurrences. Satellite images were used to document populations that became extinct during the study period or in which animals lost large parts of their traditional habitat due to new urban development. This is considered particularly important in terms of conservation, as future generations would otherwise see the absence of wildlife in cities as normal, an effect known as shifting baseline syndrome. The Court of Justice of the European Union clarified key concepts for strict species protection. These also include eco-offsetting, i.e. creating habitats to replace ones lost to development, which was already applied before a recent construction project was implemented. On the occasion of this project, the application of eco-offsetting to protect the local ground squirrel population was documented and critically discussed.