Dutch species first: Brabant battles American bullfrog

First there was the invasion of the American crayfish, and now the American bullfrog may be providing a new threat to Dutch native species.

Traces of the bullfrog, an invasive species, have been found in a Brabant nature reserve, Jeroen Delft of herpetology research institute RAVON told broadcaster NOS.

Delft and his fellow researchers are keeping a close eye on developments both in the Netherlands and nearby Flanders, which is currently combating a bullfrog invasion of its own.

The American bullfrog will “eat anything that will fit into its mouth,” Flemish researcher Lucas van Passel said. “That includes waterfowl chicks, salamanders, and anything else it comes across. Apart from that, it carries diseases, fungi, and viruses.”

Van Passel and his team have been successfully fighting the spread of the bullfrog by catching them in nets and killing them, he said.  “We see it as an oil spill that has to be contained. And it’s working,” he said.

“This year, we will focus on getting a grip on spread here in Brabant. We will be in frequent contact with our Flemish colleagues to see what they are doing,” Delft said.

It is not the first time the bullfrog has invaded the Netherlands. In 2018, the Netherlands was declared bullfrog-free after they were found and dealt with in Limburg.

The same cannot be said for the American crayfish, which are continuing their quest for dominance of Dutch waters despite many attempts to make life more difficult for them.

The crayfish – Procambarus clarkii, or red swamp crayfish – are thought to have travelled from their native United States in the ballast tanks of large freighters and are well adapted to local waterways. They are – currently – particularly common in Utrecht, Noord-Holland and Zuid-Holland.