One of France's celebrated and controversial brown bears, introduced from Slovenia, has been found dead in the Pyrenees.

Experts say the animal, aged just 11 – who boasted actors Gérard Depardieu and Fanny Ardant as "godparents" – appeared to have fallen.

Balou was in competition with the alpha male of the southern European mountains, 26-year-old Pyros, who is believed to have fathered all other males in the region and is jealously protective of his harem.

Spanish officials are considering castrating or segregating Pyros – one of the oldest bears roaming the mountains – amid fears that his sexual dominance is threatening the genetic diversity of the species.

Pyros had previously excluded Balou from his bear group, leaving the younger male alone. He was frequently spotted wandering huge distances between France and Spain in search of a mate.

"The theory that he fell seems the most probable from the initial information we have been given. He was found in a relatively dangerous area and had injuries to the back and one of his paws consistent with a fall," the local prefecture announced.

The National Office for Hunting and Wild Fauna said it had sent specialists to the area after the Réseau Ours Brun (Brown Bear Network) reported seeing the body of a bear. Experts confirmed it was Balou, named after the clownish bear in Rudyard Kipling's Jungle Book.

An autopsy is under way to establish the cause of death.

The Pyrenees mountains are one of the last great strongholds of the European brown bear in southern Europe. There are about 22 animals in the area, all of them from Slovenia and reintroduced as part of a controversial government programme after the last female brown bear native to the Pyrenees, Cannelle, was shot dead by hunters in 2004.

Pyros was born in Slovenia in 1988 and released into the French Pyrenees in May 1997. He was already the dominant male in his group in Slovenia and immediately impressed the female bears – and researchers – by his ability to reproduce. He is the father of nearly all the bears born in the mountains since 1997.

Balou was born in Slovenia in 2003 and released in 2006 wearing a tracking collar. He appears to have established his territory in the east of Pyros's domain but was, according to trackers who last filmed him last month, mostly alone. He was the only male in the area not fathered by the older bear.

The French authorities say bears are a native species and should be present in France. Farmers counter that the bears are unwelcome and kill their livestock. Several bears have been shot by hunters, allegedly by mistake. Balou was injured in a shooting in 2008.

Brown bears originated about 600,000 years ago in China and were first reported in Europe about 250,000 years ago. They are the same species – ursus arctos – as the American grizzly.

• This article was amended on 12 June 2014. The earlier version said "the last of France's indigenous brown bears, Canelle, was run over and killed in 2006"; the picture caption including that information was also corrected.