Fight against the bullfrog: Volunteer divers in action!

Fight against the bullfrog: Volunteer divers in action!

North of Karlsruhe, in the idyllic surroundings of Linkenheim-Hochstetten, the fight against the invasive bullfrog is heating up. The native amphibian species obviously feels right at home in the region, which is a real problem. The North American bullfrog (Lithobates catesbeianus), which was introduced here in the 1990s and can grow up to 20 cm in size and weigh almost 1 kg, has no natural predators and poses a threat to the native species. Fighting this species is therefore a top priority SWR reports.

To control the bullfrog population, an innovative research project is being launched using trackers and specially trained dogs. 19 volunteer scuba divers are currently collecting bullfrog tadpoles in the Streitköpfle quarry pond in order to learn more about the spread of this invasive species. State Secretary Andre Baumann from the Baden-Württemberg Ministry of the Environment is actively interested in what is happening and supports the measures.

The combat methods

The measures to combat the bullfrog are varied. Recreational divers and biologists use small-caliber weapons to remove the animals. Since 2016, an average of 4,500 tadpoles have been caught from the quarry lake every year. In just 20 minutes, the divers can retrieve up to 330 tadpoles from the water. A comprehensive removal of reproductive females should help to sustainably prevent egg-laying.

But it's not just diving that's on the agenda: from autumn 2025, species detection dogs will also be used to help track down bullfrogs in their winter quarters. The Karlsruhe Regional Council sees itself as having a duty to actively implement the legally prescribed measures to combat this. Although extinction of the bullfrog is considered unlikely, the city's goal is to control and reduce its population.

Criticism and challenges

However, the control methods are not only met with approval. Some anglers express concerns and believe the measures are ineffective. Nevertheless, the regional council remains stubborn when it comes to maintaining the balance between combating invasive species and protecting native animals. The area around the quarry pond is considered a strong distribution area for the amphibians, and both specialists and volunteers are required to prove their skills here.

The bullfrog is spreading not only locally, but also throughout the entire Rhine plain, as Süddeutsche reports. Future research, which will last until 2026 and will even equip the animals with transmitters, should help to better understand their behavior and movements. The nature around the quarry lake is both vibrant and challenging, with storks circling over the lake and the sounds of fishing boats and occasional shots from a nearby shooting club in the background.

The challenge faced by the invasive species has not only an ecological but also a social dimension for the region. Successful management of the bullfrog could not only guarantee the preservation of the native species in the long term, but also ensure the quality of life in the region.