For centuries, the Tagus River (Between Spain and Portugal) witnessed the silence of an absence. Its waters, once a refuge for a creature that engineers ecosystems, had been orphaned of its presence. However, the passage of time has finally seen the return of the beavers.
In June 2024, in the heart of La Alcarria, a team of researchers made an unexpected discovery: the return of the European beaver (Castor fiber) to this river basin, from where it had disappeared hundreds of years ago.
Confirmation of the beavers’ return to the Iberian Peninsula
This finding was confirmed by researchers Marco Ansón and Celia García Prendes, who, during an expedition to study the kingfisher, spotted this rodent crossing the river. “I saw a beaver and identified it immediately. I knew it was a significant discovery, as until now there were only records in the Ebro, Duero, and Guadalquivir, but never in the Tagus,” Ansón explained to EFE news agency.
Subsequent studies confirmed that it was not an isolated case. Along the riverbank, researchers found multiple signs of their activity: gnawed branches, partially stripped trunks, and footprints in the mud. According to their estimates, the beavers could have been inhabiting the area for at least three years, although the exact population is still unknown.
History and conservation of the European beaver
The European beaver is the largest rodent in Europe, measuring up to 90 centimeters in length, with about 35 of those belonging to the tail, and weighing between 15 and 30 kg. Although human pressure and hunting led it to extinction in this region, there are records confirming its presence since Roman and Visigothic times.
In the rest of Europe, the species also experienced a dramatic decline until the 20th century, when conservation efforts began. In Spain, their reintroduction dates back to 2003 when specimens were released into the Ebro basin without an official management plan. Since then, their presence has grown, gradually colonizing other rivers.
Challenges and future management
Despite the good news, there are still unanswered questions. How did these beavers reach the Tagus? Given that the nearest colony is over 100 kilometers away with no intermediate records of their presence, researchers suspect that they were introduced by human action.
The challenge now is to effectively manage this new population. The authorities of Castilla-La Mancha have begun monitoring the situation to assess the impact of the beavers in the area. So far, no significant damage to crops or infrastructure has been reported, reinforcing the possibility of a sustainable coexistence between this species and local communities.
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