Experts in the Netherlands are puzzled by a huge number of field mice falling to their deaths from an aqueduct.
According to reports hundreds have been found in recent weeks - but no one knows why.
The strange phenomenon is happening in the city of Hommerts, where grim pictures show dozens of dead rodents strewn across the pavements.
On Monday, Sneeker Nieuwsblad reports, 351 dead animals were found around the aqueduct.
The previous day 140 of them were found.
But no one knows who is responsible for solving the problem, or who should clear the mouse corpses up.
It is unclear why they are dying in such high numbers, although some believe they are meeting their deaths after nearby farmers flood their fields.
Forced to move in big numbers, they are heading towards what they believe is safer ground.
One mouse expert reckons it's because the mice are being chased.
Nico Beemster told AD : "If space is limited, young animals are forced to look for their own place.
"If they are then chased by a competitor, I can imagine that they will fall over the edge."
Ecological adviser John Melis told Omrop Fryslan : "It just seems that if those mice want to go from one side to the other for some reason and do not stop at the edge, which they should normally do, but just walk on.
"They then fall down they are injured or walk on again."
