Bat colonies choose Endesa

Bat conservation (chiroptera) is an outstanding issue in Spain and a topic is arousing interest in Europe. Their troublesome decline and their ecological importance as a bioindicator of the healthiness of ecosystems, as well as their work at reducing plagues and regulating insect populations make it a mammal of great importance that should be protected, in accordance with the IUCN (International Union for Conservation of Nature).

32 chiroptera species have been found breeding, hibernating or being reproduced. All these species are included in the Spanish List of Wild Species with Special Protection: twelve are considered to be vulnerable, and one (Myotis capaccinii) is endangered. Fourteen of them are classified within the Habitats Directive (43/92/CEE); eleven in Annex II (species of Community Interest) and the remaining three in Annex IV (Species of Community Interest that require strict protection).

Tunnels in hydroelectric power stations are typical bat habitats due to their combination of darkness, quiet, humidity and even temperatures in winter and summer. Bat colonies have been found in Endesa facilities on many occasions, particularly in side tunnels or access tunnels to gates. In some cases, the type of tunnel closure makes it hard for them to get in and breed. This situation it is improving by suiting them to make them perfectly compatible with the infrastructure management.  

With the Endesabats Project, and working with experts from the Laboratorio de Biodiversidad y Conservación Animal del Centre Tencològic Forestal de Catalunya (Biodiversity and Animal Conservation Laboratory at the Catalan Forestry Technology Centre), we aim to gain more knowledge and improve conservation of cave-dwelling bats, their ecological requirements and how they affect hydroelectric power station operations. We also want to emphasise the importance of these infrastructures for endangered chiroptera species, and to propose management measures to help their conservation and their presence in this type of facilities as well.

The study has been conducted in a number of phases:

• In 2013 and 2014, there was a study of the populations of bats that lived in the power stations and in the infrastructures located up-river. In 2015, the study focussed on the middle stretches of the Noguera Pallaresa, Noguera Ribagorzana and Valle de Arán river basins. An inspection of the shelters was made, a census of the populations was taken and a characterisation study of individuals was made. That year, 918 bats of 11 different species were captured, of which four were considered vulnerable and one (66% of those captured) in danger of extinction (Myotis capaccinii), according to the Spanish Catalogue of Threatened Species. We also realised that more than 60% of the galleries studied had been inhabited at some point by bats.
• In 2015, an important colony of bats was discovered in one of the galleries belonging to the power station in Camarasa (Lleida) with approximately 400 individuals of Myotis Capaccinii, and about 200 individuals of the species Miniopterus shreibersii, all of them considered vulnerable. In the following years, Endesabats continued to focus on the study of installations located in down-river stretches and on monitoring the most important colonies discovered in previous years.
• During 2019, we continued with the sampling to increase the information we have on the bats in our installations. This involved studying the population of bats in power stations in Galicia and the population dynamics of the colonies of the Loong-fingered Bat (Myotis capaccinii) and their movements between areas in the Mequinenza region.
• In that same year, 1,190 bats of 13 different species were captured in 4 localities (3 in Galicia and 1 in Catalonia). 4 female long-fingered bats were tagged with transmitters to study their hunting areas and find other breeding colonies in the Ebro and Segre rivers. This resulted in the location of an important breeding colony of 1,000 individuals in an old mine in the municipality of Serós.
• In 2021, we incorporated twelve recorders to monitor the behaviour of the colonies established in the areas surrounding our hydraulic power plants. These devices were developed by the Centre for Forest Science and Technology of Catalonia (CTFC in Spanish) in collaboration with the Museum of Natural Sciences of Granollers, and they enable sounds to be recorded one night a week without the need for human interference. By reducing intrusiveness, much more real information is obtained about the behaviour of these species:
• In Aragón, these devices were placed in different caves and tunnels of water origin and in Catalonia they were installed within the surroundings of the Camarasa and Canelles power plants. With the data extracted during the first months, we have been able to ratify these locations as mating refuges of great importance, as well as establishing very precise phenological patterns. In Galicia, we studied 8 of our infrastructures (Campañana, Peñarrubia, Eume, Quereño, Ventureira, Ribeira, Bárcena and Cornatel) and found more than 15 species of bat that we identified by capturing individuals and taking ultrasound recordings.
• In 2023, light sensors were installed that detect and count the people entering different caves linked to hydraulic installations in Catalonia (in the Noguera region) to determine whether or not human presence has an impact on the colonies of bats. The results obtained will be cross-referenced with the data collected with the sound recorders and camera traps that were also installed to be able to draw better conclusions and contribute to the conservation of the bats. 

This project highlights the key role played by the infrastructures of most of the plants providing shelters for bats, enabling them to successfully complete their life cycle (breeding, mating and hibernation). It also shows how reservoirs favour the community of bats by providing them with hunting areas, such as the calm waters that are concentrated in the dam, and the riverside forest that thrives in the vicinity.

These years of study and data collection are enabling Endesa to take a number of actions to adapt hydraulic installations and be able to protect bat colonies. These measures include the following: Conditioning the entrances to the tunnels, installing specific shelter boxes and reducing luminosity in certain points that are critical for bats.