For generations, shepherds in the region have steered sheep up the mountains in summer to graze on higher pastures, against breathtaking backdrops of sheer precipices and plunging valleys.
But the arrival last year of two more bears – brought over from Slovenia to boost the area's tiny bear population – has made the herdsmen jittery.
Clouding the bucolic scenes of sheep grazing in mountain meadows is the fear that the bears, one of whom has already killed several sheep in the region, will strike again.
“Before we took the sheep up, there was an uneasy atmosphere in the valley,” Nicolas Bengoechea, part of a father-and-son shepherd team that keeps watch over a flock of 1,500 sheep, told AFP.
France's growing bear population, like its burgeoning wolf population, is a source of tension in mountainous areas, pitting farmers against the authorities and animal rights activists.
The state began reintroducing brown bears from Slovenia about 20 years ago in a bid to increase numbers of the omnivorous mammals, which had been hunted to near extinction.
Last October, two female bears were helicoptered into the western Pyrenees, bringing the total bear population in the French Pyrenees to an estimated 40, up from just five in 1996.
Since then, one of the bears has given birth to two cubs.
The new arrivals received a hostile reception, with farmers blocking roads and scattering bloody sheep remains in front of a local town hall in protest.
“When I saw the bear in that cage in October, I knew that eight months later, it would be on my farm,” said Nicolas.
The young shepherd's grim prediction came true when one of the bears, Claverina, killed one of his sheep and sent the rest bolting into the distance on the family's enclosed meadow in April in the border village of Larrau.
Local authorities later told Nicolas he had been a victim of “bear damage”, with Claverina's GPS collar revealing her to be the culprit.
With Claverina having already killed eight sheep on the Spanish side of the border in May, shepherds are sleeping fitfully.
From around 30 huts dotted across the Iraty border area, shepherds take turns watching over the 80,000 sheep and cattle that spend June September mowing the mountain pastures as part of the summer migration known as the “transhumance”.
Nicolas and father Jean-Marc's perch are grassy hills at the foot of the Pic d'Orhy mountain, 1,300 metres above sea level.
While the French government compensates farmers affected by bear attacks and subsidises the pay of extra shepherds, its recommendation to keep sheep locked up in pens overnight would spell the death of transhumance, said Jean-Marc.
“Putting 1,500 sheep in enclosures would mean bringing them down (from the mountain) every day. It would be hell,” Jean-Marc said.
The farmer also voices “strong doubts” about the ability of enclosures to prevent bear attacks.
“It doesn't work in Ariege, so I can't see why it would work here”, he said in his sing-song southwestern French accent, referring to a region 280km east of Larrau which has been the scene of repeated bear attacks.
In June, more than 250 sheep plunged off a cliff to their deaths after apparently being chased by a bear.
A similar incident last month, in which 61 sheep fell off a cliff, prompted local authorities to declare a low-level bear alert, allowing farmers to use lights and whistles to scare away the creatures.
Farmers can also shoot but not kill bears if local authorities declare a high-level alert.
But for Nicolas, protecting flocks from bears is the responsibility of the state rather than farmers.
“I'm not going to be the one going out shooting bears. Who knows how it would react!”
If the bear population continues to climb, he said he will stop taking sheep up the mountains.
“And then I'll no longer be a shepherd,” he said.