The only brown bears that have managed to dodge extinction and move forward in Spain without reintroductions of foreign specimens are those of the Cantabrian mountain range, distributed in two subpopulations: the western and the eastern. But with different luck. While in the western part it is estimated that there are around 250 specimens, with 35 females and 64 pups in 2017, in the eastern one, it drops to about 40, with six females and nine pups, according to the data of the Junta de Castilla y León. Both groups are separated by a strip of between 50 and 80 kilometers. The other redoubt, that of the Pyrenees, with 44 copies, shared with France and Andorra, comes from the transfer of Slovenian brown bears of the same species (Ursus arctos arctos). The last autochthonous bear died in 2004.
Despite the years of study, the reasons for the differences in the population growth of the two subpopulations, which are distributed in the communities of Asturias, Galicia, Cantabria and Castilla y León, have still not been clarified. Guillermo Palomero, president of the Bear Foundation Pardo (FOP), focuses the problem on the habitat. "The mountain of Palencia is less productive because of the type of food. In the autumn the bears depend on the oaks and beech trees, while in the western zone they have chestnuts, acorns, beech … They have a greater guarantee to endure the winter, "he explains. Remember also that when you started to manage the bear, there were more individuals in the western area with more individuals. "In the worst years," clarifies Castilla y León, in the western part they survived between 50 and 60 specimens and at least 10 reproductive bears. In the east, however, the population dropped to about 20 and no more than two breeding bears. A circumstance that increased their consanguinity.
The Fund for the Protection of Wild Animals (Fapas), which is also dedicated to the conservation of the bear in the Cantabrian mountain range, warns that in the eastern part the mortality is greater. "There is a continuous trickle of deaths linked to the hunting activity. If they were natural, the corpses would not be located, because it is an animal that covers itself if it is sick or injured, "says Roberto Hartasánchez, president of the organization. "It is a less rustic environment, so if you open clues, as has happened, reduce the places of refuge and the bear needs quiet places," he says.
This year is being especially tragic. Four dead specimens have been discovered in the eastern zone. "We are waiting for the necropsies, if they give them to us, because you can not lose that many bears like that, all at once," complains the president of the FOP. He discards, however, hunting or poaching as the source of the problem. "It would be the same in the western part, where there is more human pressure," he says.
For four years now, research group formed by experts from the Higher Council of Scientific Research (CSIC) and of the University of Oviedo, they study the case of the Cantabrian brown bear. Vicenzo Penteriani, head of the team, believes that from the point of view of resources, both in terms of food and habitat "there is not so much difference as to explain the inequalities in the growth of the species between both areas". In addition, it maintains the productivity of the females is similar, therefore, the reason for the disparity in the number of specimens is not there either.
The FOP shows its doubts in this regard, because their research indicates that the Cantabrian females are less prolific than is usual in the species. The western bears return to win, with an average litter size of 1.87 puppies, while the Eastern ones remain at 1.5. The FOP biologist Fernando Ballesteros explains that his techniques may not be very sophisticated, but the fact of having so many years of observation -from 1989- makes his data "very robust".
Ballesteros maintains that the "trend of today is relatively similar between both populations". A good news to which it is necessary to add that both groups are mixing, with some incursion of males from the western part to the oriental one, verified with analysis of feces and hairs. The plantigrades will be more complicated to communicate with the population of the Pyrenees. "There is no easy connection," says the CSIC researcher.
The main objective of the researchers of the CSIC is to obtain the authorization to undertake a radiolabelling campaign, which they consider to be decisive in order to obtain more specific data of the species. "You can not raise a management program without knowing where you start from," warns Penteriani. The conservationist Hartasánchez shows his agreement, because "they would give fantastic information". From Fapas, however, they warn that radiolabel should be selected to answer specific problems.
"But it's a taboo subject, because 20 years ago they started a similar project and it went wrong," explains Penteriani. A bear died days after being captured in a trap in the Somiedo Natural Park (Asturias) to install a radio transmitter and the controversy was unleashed on the relevance or not of the method.