Dutch water boards say they have increased their efforts to combat muskrats and coypu after their number spiralled following last year’s wet weather, catching nearly 68,000 last year.

Muskrats and coypu, which are not native to the Netherlands, cause flooding by tunneling through dykes and other coastal and river defences.

They also threaten biodiversity by eating  reeds and bulrushes, which are the main food sources of black terns, bitterns and reed warblers.

In 2024, the combined 21 water boards caught a total of 65,811 muskrats, some 15,000, or 29%, more than in 2023 while 1,862 copyu were trapped and killed, 13% up from 2023.

Long periods of high water levels in Germany deprived the animals of their burrows prompting them to find shelter further downstream in the Netherlands. Most were caught in the border area with Germany.

The Netherlands has had no coypu population since 2013, with 95% of the invasive species caught at the border while the aim is to make sure no viable population of muskrats exists by 2034. That means that cross border agreements will have to be in place to make that happen, water boards spokesman Vincent Lokin said.

“We have some 3,500 kilometres of dykes to protect the Netherlands from flooding caused by high seas, rivers and lakes. Weather extremes will only make this worse. Preventing muskrats and coypu from damaging these dykes remains the priority of our team of 400 specialised catchers,” Lokin said.

Muskrats and coypu are not the water board’s only headache. American crayfish are causing major damage to weirs and the banks of ditches and canals and their number is thought to run into the billions.