American bullfrog expands habitat to Limburg
In order to monitor the distribution of American bullfrogs in Flanders, INBO carried out an eDNA-screening in the surroundings of the nature reserve De Rammelaars by order of the municipality of Ham. In 6 of the 15 ponds examined, American bullfrogs were detected. Until now, this invasive exotic frog species was only known to be present in the neighbouring province of Antwerp.
The American bullfrog has been able to establish itself in Flanders since 2000, probably through introductions into garden and natural ponds. Since then, this huge frog has expanded its habitat in the province of Antwerp over dozens of kilometres and hundreds of ponds, mainly in the valley of the Grote Nete. The voraciousness of this invasive exotic species combined with the absence of natural enemies has an enormous impact on native species. In addition, it is feared that the frog is spreading germs that are harmful to our native amphibians. To stop the further spread in Flanders, several eradication campaigns have been launched since 2012. One of these is the LIFE 3n-bullfrog project, in which an integrated approach is central.
Recently, the suspicion grew that bullfrogs had also set foot in the province of Limburg. We were able to confirm that suspicion with this research. For the time being, it is only a few individuals, probably defectors from the large bullfrog population around Balen. They could have ended up in Limburg along the Dessel-Kwaadmechelen canal.
Based on these findings, the province of Limburg will release additional funds for further screening and the start of an intensive control programme. The Life project will coordinate this. The aim is to prevent the definitive establishment and expansion of this invasive exotic species in Limburg at all costs. This approach is therefore a good example of an early-detection-rapid-response system in practice, and how eDNA analysis can play a key role in this.
Rein Brys, Teun Everts en Sabrina Neyrinck
Photo above: American bullfrog (foto Rollin Verlinde - Vildaphoto)