American bullfrog now definitely turning up outside known areas too
The American bullfrog is a non-native invasive species that arrived in Belgium from North America. This frog threatens native species through competition for food, predation and disease. The valley of the Grote Nete in the Antwerp Kempen region forms the main stronghold in Flanders. There are also smaller isolated populations in Arendonk and Huldenberg. In all these places bullfrogs are already being actively controlled.
Earlier sightings were also reported outside this known range, such as in the Zegge (Geel) (since 2001), Ravels (2006), Mol (2021), and the Rupelstreek (2024) in Antwerp, the Dommelvallei in Limburg (2006), and between Aalst and Ghent in East Flanders (1997). Because these were often one-off observations that were not verifiable, alarm bells failed to sound.
To keep a finger on the pulse, INBO monitored the wider environment of these sightings, as part of the LIFE 3n-bullfrog project. Environmental DNA (eDNA) allows us to cost-effectively investigate the presence of a species in larger areas. In the past, we could only rely on sight observations. From this study came the alarming confirmation of the presence of bullfrog in several water bodies in all the above regions. The strength of the eDNA signals picked up indicates latent invasion stages at an early stage at all sites surveyed, provisionally without successful reproduction. To prevent permanent establishment and expansion, rapid intervention and additional eDNA monitoring are now crucial .
Teun Everts, Charlotte Van Driessche, Rein Brys
Image above: bullfrog (photo Rollin Verlinde - Vildaphoto)
