De ringslang in Amsterdam, historie, onderzoek en dertig jaar broeihopen

The grass snake in Amsterdam; history, research and 30 years of creating egg-laying heaps This article discusses the history, methods, results and future of the ‘Amsterdam’ breeding heap project and other conservation measures concerning grass snakes (Natrix helvetica) in Amsterdam and surrounding areas. Until the 1940s, Amsterdam still had a connected habitat without any real obstacles. Since then, construction of infrastructure and residential areas has resulted in habitat reduction and separation between populations in the region. In 2012, the Amsterdam City Council established the Ecological Structure of Amsterdam. Ecopassages have been constructed specifically for the grass snake in various places. Studies have shown that these measures are effective. The number of traffic victims has drastically decreased. The first six egg-laying heaps for the grass snake were constructed in Amsterdam and the surrounding area in 1994. Thirty years later, this number has increased to a total of seventy heaps. Between 1994-2022, more than 98.000 eggs were counted, of which almost 87.600 eggs hatched. For a complete overview of all the results, please refer to the digital map ‘Ringslangen - locations breeding heaps’ (see: https:// maps. amsterdam.nl/ringslang/). Without the efforts and enthusiasm of hundreds of volunteers, this would not have been possible. This paper highlights how city councils and citizens can work together over extended periods of time in order to achieve a common goal: the conservation of grass snakes in an ever urbanized environment. In 1994 werden in Groot-Amsterdam de eerste zes broeihopen voor de ringslang aangelegd. Dertig jaar later is het aantal broeihopen in Amsterdam en omgeving uitgegroeid tot zeventig. Dit artikel gaat in op de geschiedenis van de ‘Amsterdamse’ broeihoop, de resultaten, het recept en de vrijwilligers. Het gaat ook over het opheffen van knelpunten, de lange traditie van onderzoek en de verspreiding van de ringslang in de Amsterdamse regio en wat betekent Rokjesdag in Amsterdam?