"This year, the number of voles increased immeasurably," Ernst Romang notes. In Turbach, the extent of the vole plague is evident: meadows littered with churned-up soil look more like fields than pastures.

Such an invasion occurs in a cycle of about ten to twelve years, says Toni Reichenbach. "The spread of the rodents increases every year until it finally reaches its peak," he explains. Due to inbreeding and lack of food, the population eventually collapses. Reichenbach is convinced that the plague will end this year.

Unexplained cause, significant consequences
The reason for the exponential increase in the mouse population is unexplained. Reichenbach suspects that the mild winter temperatures favour reproduction. The voles begin their mating phase a few weeks earlier than usual, which consequently drags on.

The plague results in a considerable crop loss. "The rodents eat all the roots below the surface," explains Romang. As a result, the farmer has to sow new grass to secure the yield. The cows also suffer from the rampant disaster: Due to the loosened soil, the animals sink in and cause massive damage. They are usually only taken out to pasture in dry weather when the soil is firm. The cultivated field no longer yields much grass anyway, which increases feed costs for the farmer.

Traps and gas machines
Farmers can delay the infestation by using mousetraps at an early stage. Above a certain population density, however, the result is more like a drop in the ocean. "Last year, I caught 600 voles, but even ten times that number would not have been enough," says Reichenbach, illustrating the devastating situation.

Gassing proves far more effective: a sensor locates the subterranean vole tunnels, which the machine then fills with gas. Reichenbach warns, however: "Despite its effectiveness, this option should be taken with caution. After all, the gas also affects the composition of the soil." Besides mousetraps and gas machines, only one measure works reliably: Wait until the mice population decreases by itself.

Based on AvS/Sophia Grasser