The valleys of Yerse and Aguée via Arriousec to Peyras

This route requires you to leave one vehicle at the finish (E) (Peyras, Monastère de Béthléem, in Saint Pé-de-Bigorre) whilst the other takes you to the starting point (S).
For the starting point, take the road leading from Nay to the Col du Soulor. After Arthez-d’Asson, head for the hamlet of Les Aoules.
Park near the houses in the hamlet known as l’Arriou-Sec.

(S) Take the path, marked in yellow, which follows the course of the Arriou Sec stream upstream. The climb is gentle.

(1) At the Ravin de Castéra, take a dip in the spring of the same name (marked by a sign and several markers in the trees).

(2) Pass through the Ravin du Monbula, which is more striking than the others.

(3) At the 812 m mark, fords the Arriou Sec and begins a steeper climb towards the summer pastures.
Depending on your pace, 1½–2 hours after setting off, you’ll reach the first mountain pastures at an altitude of around 1,000 m.

(4) You’ll soon find yourself back in the woods for a short while.

(5) A quarter of an hour later, you’ll emerge onto the large mountain pastures.
From there, progress may be hampered by ferns and brambles in the middle of the path.
It is the outcrop of the Sainte-Suzanne marl (black, schistose rock, often yellow on the surface due to weathering) that encourages the growth of grasses particularly favoured by livestock.
You will then reach the stream bed, which you cross and follow until you turn off towards the Cabane de Yerse, situated on the left-hand side.

(6) The Cabane de Yerse nestles on the heights of the valley of the same name, right in the heart of the mountain pastures at an altitude of 1,275 metres, overlooked by the Pic d’Estibette (1,851 m). It has been beautifully renovated in true mountain style, although an attic floor has been added, which does not detract from the overall appearance.
It is open all year round to walkers, cavers, photographers and herders.
After a well-deserved break of a good quarter of an hour, it’s time to set off again, as it’s a long way to go – this isn’t the place for a midday snack!

You have the choice of heading back down into the valley floor or staying on the contour line to reach the Col d’Espadres, which can be seen to the east.

This unmarked route largely follows the contour line, taking us through the young beech forest that stretches across a magnificent and vast sharp limestone pavement. This marks the boundary between the limestone rocks of the karst landscape and the marl of Sainte Suzanne. It is along this boundary that the most remarkable cavities (chasms, etc.) are generally found; the route passes close to several of them.

(7) 25 minutes after the Cabane de Yerse, you reach the Col d’Espadres.
Whether to the east, towards the Aguée, or to the west, towards the Yerse, the view is magnificent and the place is steeped in mystery. Herds of horses are often found here, and sometimes with donkeys.
In winter, a snowfield blocks the eastern face of the pass, hindering the descent towards the Aguée. But in summer or autumn, there’s no problem at all!
So continue the route by descending the pass towards the head of the Aguée valley, either passing north of the ruined Espadres hut or to the south amongst the sinkholes, several of which have collapsed or are flooded by the numerous nearby springs.
Descend at a leisurely pace through the entire Aguée valley, along unmarked paths or cattle tracks, through an area with little or no woodland. Find a lovely, lush meadow to enjoy your long-awaited snack.
Then resume the path, passing close to old shepherds’ huts (ruins or traces) and reaching a large clearing at 960 m, with a grassy area sloping up the southern hillside of Sarro Pourcou (Serre Pourcou), the mountainous ridge that overlooks the Aguée to the north and ends at Cap des Litas (1,300 m) to the east.

(8) Continue eastwards until you reach the edge of the forest at a place known as ‘Cul de l’Aguée’.

(9) Of the various streams in the Aguée, one of them disappears into a small sinkhole in the middle of a large pool covering a few square metres beneath the beech forest.
A path leads off from here to the Picharrot waterfalls, but as it is difficult to follow in this direction, it is best to avoid it.
Including breaks, it took me 5 hours to get there from Arriou Sec.
Turn back to the large clearing you crossed shortly before.

(8) Head up to the right, through woods and bushes, climbing almost 300 metres in altitude to Cap des Litas. Avoid getting too close to the edge of the State Forest (green line on the map), as a few rocky outcrops make progress difficult.

(10) Descend the opposite slope through fairly sparse woodland and head towards the bottom of the valley, known as Bat Séco or Cabane des Italiens (names not shown on the IGN map).
At the 1,130-metre mark, in the middle of a vast beech forest, you reach the bed of the Ruisseau de la Fontaine d’Ariails (not shown on the IGN map); the path then branches off eastwards, joining the bank of the Ruisseau de la Gargante at the 969-metre mark.
Here, amidst the beech trees, it is the bed of a small, gentle stream, but further downstream it becomes a deep, impenetrable and treacherous ravine flowing into the Génie Longue!
Here you’ll find the yellow markings (wide and quite old) for the Nature Reserve and a blue marking (recent) for the Saint-Pé Integral Biological Reserve (RBI).

(11) Here you have the choice of heading back into the valley via the Tachouères (badgers) path on the right, which seems quicker in terms of time but is an infinitely longer route, or the Aülhet path, which involves a slight climb. This particular walk favours the latter.
So turn left, carefully following the yellow markings clearly marked on the trees.
The route passes south of the Soum de l’Artigue, at a clearing with a watering trough, at a place known as Hount-Débat.

(12) You’ll reach the Cabane d’Aülhet without any difficulty; it has been clad in new timber panelling (since October 2016).
Then take the yellow-marked path (recent but very narrow) which descends from the mountain pastures to Peyras, via an ancient pastoral track that is quite steep and very slippery in wet weather. If the weather is dry, runners will be able to give it their all.

At the Pla dé Bers junction, at an altitude of 824, leave the Tachouères path on your right and continue straight up the slope to reach the car you left there that morning or the kind soul who has come to collect you (S/E).

As is often the case, I’m taking you along little-known, unmarked paths that can sometimes be rather hostile to walkers: particularly here, along the edge of the Picharrot cliffs and the heights of Sarro Pourcou.
Sarro Pourcou, or Serre Pourcou, is this vast expanse of forest on the ridge (the serrat) of the mountainous hilltop stretching from the Col d’Espadres to the Cap des Litas.
All these ancient places, their shepherds and, at times, the paths are briefly described by Abbé B. Abadie in his 1969 book *Le Sanglier du Picharrot*.

Warning!
This hike takes place in the heart of the wilderness in an environment that can be challenging: steep slopes, rocky outcrops, crags, thorny undergrowth, and at times a complete lack of signposting or even a proper path… This is why it is reserved for experienced walkers with a good sense of direction. A GPS device may also prove very useful.
Shortly before waypoint (7) and up to waypoint (11), there is no marked path on the map. However, this does not mean there is no path at all…
Furthermore, the Visorando track for this hike between the WPs (10) and (11) is only approximate due to poor satellite reception in this area.
I have classified this hike as “Difficult” due to the difficulties described above, particularly the numerous sections off the beaten track and without signposting, and above all because of its length and elevation gain. It is a challenging route, suitable only for experienced hikers.
In winter, if there is snow, the difficulty rating would rise to ‘Very difficult’.

Estimated time
I completed this route in just under 8 hours, including breaks and a picnic. This is a reasonable time, given the route’s difficulties, but also the time spent exploring around the Porto de la Gleize (below the Col d’Espadres) and the Cul de l’Aguée. So set off early and allow at least 8 hours to be on the safe side.

Water sources
There are no fountains along the route known to provide drinkable water.
However, the one at Castéra is acceptable, as no livestock graze nearby.
If necessary, from June to October, you can top up your supply of non-potable water at the Yerse hut (there’s a tap nearby) or at the Aülhet hut, and boil it to make it safe to drink.
You should be wary of all other springs or water sources you come across, as drinking water in the mountains is not guaranteed to be risk-free...

Places to stop and take shelter
In the event of heavy rain or thunderstorms, the two mountain huts (6) and (12) are the only places offering proper shelter along the route. There are also a few makeshift shelters provided by low walls or rock faces dotted here and there.

Equipment
Bring the usual equipment for a mid-mountain hike (hiking boots, suitable clothing, rainwear, water, food, a survival blanket, a knife, a compass, a map, a whistle, a GPS, etc.).

Visitor numbers
In spring and summer, between waypoints (WP) (S) and (7), then (12) and (E), you may come across a few hikers, cavers, shepherds or the occasional livestock farmer. Very rarely anyone in winter.
Elsewhere, the route is completely deserted, in both summer and winter, apart from herds of cattle, sheep and horses from June to November.

Spelling of place names
Several place names are spelled in different ways: in Occitan, Bigourdan, Gascon, Frenchified Gascon, French, distorted IGN spelling, etc.

Flora and fauna
The vegetation of this mountain range reflects the severity of soil drought caused by the terrain and the highly permeable nature of the subsoil
which are highly permeable, but this is offset by very high rainfall and cloud cover: boxwood, beech, lime and hazel are ubiquitous… This is why the wooded slopes are very damp and can sometimes be very slippery. (source: Saint-Pé Tourist Office).
Part of the walk, between waypoints (9) and (11), takes place within the Saint-Pé ‘Integral Biological Reserve’, covering 1,010 ha of the 2,588 ha of the undivided forest of Saint-Pé (see the onf.fr 1 and Natura 2000 websites).
Regarding the rationale for leaving ‘dead’ trees in place, there are some interesting articles on the Wikipedia pages ‘Deadwood’ and ‘List of ancient primeval forests’.

With a bit of luck, you may also come across a wealth of wildlife. In particular, wild boar, roe deer, chamois, occasionally mouflon, countless birds and various insects, and sometimes amphibians (frogs, toads, salamanders).

Alternatives
You can enhance this route by:
- a detour of a few minutes via the Porto de la Gleize (and its nearby chasm), to the north between Espadres and the Source d’Arials,
- continuing beyond the Cul de l’Aguée, for experienced walkers or climbers only and with the utmost caution, to admire from above the vertiginous cliffs of the Picharrot and the deep gorges, carved out by ancient waters and perhaps still by the fury of modern storms,
- a visit to several caves, chasms and karstic caves, most of which are not marked on the IGN map (1,600 cavities are recorded in the massif), provided you have the necessary skills and equipment!

A bit of history
The forest of Saint Pé is also known as the forest of Très-Croutz (or Très-Crouts or Tres Croutz or Tres Crouts or Tres Crots).
The origin of the name ‘Très-Croutz’ is thought to derive from the ‘Trois Croix’ (‘très croutz’ in Bigourdan/Gascon) carved into the stone at a place known as ‘la Toue’, right in the heart of the massif, at an altitude of around 1,400 metres.
The Three Crosses bear witness to age-old pastoral disputes between Asson, Salles and Saint-Pé-de-Bigorre.
In 1569, the Bearnese Protestants from the Asson valley decided to attack the Bigourdans of the Estrèms de Salles, with whom they were disputing the Azun and Maumula mountains. The 1,500 men intended to lay waste to the village of Salles and seize all the livestock from Vergoun. But the battle was won by the Bigourdans. These conflicts became so serious that the King’s army had to be called in. It was impossible for the Bishop of Tarbes to restore harmony. Source: Abbé B. Abadie, *Le Sanglier du Picharrot*, published by Marrimpoey Jeune.
At a place known as “Très-Croutz”, the bishoprics of Tarbes, Lescar and Oloron converged on this mountain.
Today, all that remains are three crosses carved into a rock, along with the inscription ‘1716’. They can be found on the IGN map between the ‘u’ and the ‘e’ in ‘La Toue’.

Nearby attractions
- The town of Lourdes and the Marian shrine;
- The Batsurguère Valley;
- The village of Saint-Pé-de-Bigorre: the village itself, its cultural heritage, its events, what remains of the Très-Croutz Forest and the trails in the Pibeste-Aoulhet Regional Nature Reserve, as well as water sports;
- The story behind the reserve’s new signposting in autumn 2014;
- A little further on, the Gaves Valley

Find out more...
- It is well worth consulting the website and publications of the Pibeste-Aoulhet Regional Nature Reserve. The most notable is the “reserve guidebook”, packed with information, routes and anecdotes!
- The Saint-Pé Tourist Office also publishes numerous brochures and detailed walking itineraries. One of the brochures may be of interest for discovering the massif’s flora and fauna: the ‘Karst Trail’ brochure, even though it does not cover this particular walk.
- The former Peyras Farm, now the Bethlehem Monastery.
- You can immerse yourself in reading local books:
Abbé B. Abadie, *Le Sanglier du Picharrot*, published by Marrimpoey Jeune,
Jacques-Emile Mengelle, *Bigorre of My Childhood*,
Jean-Claude Mengelle, *Le solitaire de la Gargante*.