Donostia / San Sebastian City Council fosters the protection of bats in the Enobieta dam

11/02/2026

An EHU study characterises the colonies of bats that take shelter in the Enobieta dam in Artikutza and defines measures to minimise the impact of its future demolition. 

Donostia / San Sebastian City Council has launched a study to characterise the colonies of bats that take shelter in the Enobieta dam in Artikutza, in order to guarantee their protection in light of the infrastructure’s future demolition. The action is included in the LIFE IP Urban Klima 2050 project, as part of the actions to improve the territory’s green infrastructure and strengthen its resilience. 

The research, carried out by EHU researchers between July and December 2025, follows on from a previous study carried out in 2016, which highlighted the exceptional diversity of bats in Artikutza. Despite the reduced size of the area and the scarcity of natural shelters, such as caves or rocky areas, the study identified the Enobieta dam as a site of special interest for bats and recommended a detailed analysis of its use as a summer refuge. 

Colonies of endangered species 

The latest study has enabled the colonies that occupy previously identified inner cavities and new chambers located inside the dam to be characterised. During the breeding season, these areas are home to important colonies of greater horseshoe bats (Rhinolophus ferrumequinum) and lesser horseshoe bats (Rhinolophus hipposideros), both of which are classified as 'vulnerable'. 

Specimens of the big greater mouse-eared bat (Myotis myotis), have been detected in smaller numbers, whereby this species is included in the 'endangered' category, reinforcing the need to adopt specific protection measures during the works. 

Measures to minimise the impact of the works 

Based on the results obtained, the research team has defined a series of measures aimed at minimising the effect of the works on bat colonies. Operational objectives include avoiding direct mortality of the animals, maintaining the physical conditions of the existing shelters as far as possible and reducing factors that may alter the behaviour of the animals during and after the works. 

Other actions include adapting the demolition schedule to respect breeding seasons, involving bat specialists in the environmental management of the works and introducing adaptations to improve the conditions of the inner cavities used as shelters.