French, Italian and Swiss pranksters often describe the dahu as a mountain goat-like animal with legs of different sides having differing lengths to fit the mountain's side.
Regional variations on its name include dahut or dairi in Jura, darou in Vosges or darhutin Burgundy; also called a tamarou in Aubrac and Aveyron), and tamarro in Catalonia and Andorra. The dahu cub is called a dahuot.
In French lore, the dahu has the appearance of a deer or ibex, but with the principal characteristic that its legs on one side of its body are shorter than on the other side. This enables it to walk upright on the steep slopes of its mountain environment. It can only walk around the mountain in one direction. Legend attributes various differing descriptions to the animal, including the laevogyrous dahu(which has shorter legs on the left side, and thus goes around the mountain counter-clockwise) and the dextrogyre dahu (which has shorter legs on the right side, and thus goes around the mountain clockwise). These seldom interbreed according to French lore. However, when interbred, it is believed that there are two more types of dahu. These two variations have never been seen, but are believed to exist. These variations have the leg pairs across the diagonals. This means that the dahu can have a long front right and back left leg, or a long front left leg and back right leg. It is also said that male Dahus have legs shorter on the right side and that females have shorter legs on the left side, thus making them walk in opposite directions around the mountains enabling to find each other and mate. Also, the male dahu has testicles that drag down onto the ground leaving a scent trail for members of the opposite sex to trace. Males also use the scent trails to find their next molestation victim, for dahus are known for harassing each other to assert dominance.
French pranksters state that catching a dahu involves two people, one with a bag at the bottom of the mountain slope and another who is good at making dahu sounds. The latter stands behind a dahu and makes the noise. When the dahu turns around to see, it loses its balance and rolls down the hill to the person with the bag at the bottom.
Another method is to have pepper ground onto a large stone; when the dahu, while grazing, comes and sniffs the pepper, it would sneeze and knock itself out against the stone.
Princess Dahut of Cornouaille (Brittany), whose name is homophonous with that of the animal (but often spelled "dahud" in Breton language texts), is sometimes associated with the dahu in modern folklore, as in the following legend: One day she gave the key of her city, Ys, to the Devil, who used it to destroy that city. As a punishment, God transformed her into an animal with the odd and hairy form the Dahu has today.
The dahu is a staple of 20th-century French popular culture, known in Lorraine, in the mountainous regions of eastern France (Alpesand Jura), and in French-speaking Switzerland as a theme of jokes among natives and a spoof for fooling young children. Its popularity began to soar toward the end of the 19th century. The budding tourism industry brought to the mountains wealthy city dwellers with a somewhat arrogant attitude and a paltry knowledge of the countryside. The mountaineers working as hunting guides would take advantage of the gullibility of some tourists to lure them into the "dahu hunt" (in French "chasse au dahu"). The animal was touted as a rare and precious bounty, the capture thereof required waiting alone all night on a chilly slope, crouched in an uncomfortable position.In the second half of the 20th century, the supply of naive hunters had dried up, and the dahu hunt enjoyed a second life as a summer camp spoof.
Since the last decades of the 20th century, the dahu is widely recognized as a fictional creature, a joke, and a metaphor for a tall tale. This legend has been widely perpetuated by Swiss foreign language teachers intending to play pranks on their students. It has been adopted by other mountainous regions such as the Pyrenees. Recreational "dahu hunts" are sometimes organized as outdoor activities in France and Switzerland. There are dahu websites and dahu aficionados, such as Marcel Jacquat, former director, now retired, of the Natural Science Museum of La Chaux-de-Fonds in Switzerland, who wrote a monograph and opened on 1 April 1995 an exhibition devoted to the animal. On 1 April 1967, the Prefect of Haute-Savoie (France) officially made the mountainous suburbs of the small town of Reigner a "Dahu Sanctuary" where hunting and photography are forbidden. It was a joke, according to the 1st of April tradition, April Fools' Day. Since then, the Dahu became widely became in many parts of the french internet, including parodies and memes.