Farmers in a picturesque Swiss village are baffled after a herd of cows jumped off a cliff en masse to their deaths.

The 13 cows broke out of their pen near the Valais village of Levron, ran towards the cliff edge and either fell or threw themselves off the 50m drop, local media reported.

12 of the mostly Herens herd died in the fall, with the lucky thirteenth thought to have survived only because it landed on the other cows.

It was taken to an animal hospital in Bern to be treated for a broken jaw, while the other animals were transported to a disposal facility.

"The cows broke through several lines of wire around the pasture before finding themselves on the ridge. They fell into the void, as if they had been driven back," Norbert Terrettaz, president of a farming insurance company in the region, told local paper La Nouvelliste.

In total, the cows were thought to be worth about 20,000 Swiss francs (£16,000, $20,500). The herd belonged to several owners but were all grazing on land owned by a local couple, Aurélie Fierz and Thomas Gabioud.

The couple blamed the incident last Wednesday night (24 May) on some kind of predator who spooked the animals.

Cows wandering at high altitudes is a common sight across much of the Alps, where farmers allow them to graze on green pastures surrounding villages.

Benoît Berguerand, member of a local breeders' association, said he was baffled as to why the all the cows plunged to their deaths at the same time.

"They must have been blocked somehow," he said. "One or two cows falling off, that's possible. Thirteen, that's a new and incomprehensible phenomenon. It is unlikely that they threw themselves off without pressure."

Terrettaz agreed the incident was unusual. "Cows don't follow each other like sheep, when they are scared, they have a tendency to disperse," he said.

He gave two plausible explanations: that a dog was let loose in the area by its owner or that wolves recently spotted in a neighbouring valley had come across the herd.

There is no evidence the cows suffered any claw or bite marks, however. Four yaks who were grazing nearby were also unharmed.

"We are calling for more information," Terretaz said, appealing for any witnesses to come forward.

This is not the first time cows have been mysteriously killed while falling from a cliff edge in Switzerland.

In 2009, some 28 cows and bulls were found in a crumpled heap at the bottom of a mountainside after plunging hundreds of metres to their deaths.

The incident, in the Swiss village of Lauterbrunnen, was blamed by some locals on the cows being spooked by violent thunderstorms.