Today is the International Bat Appreciation Day, with over 1,440 species worldwide, bats are true examples of biodiversity among mammals. Approximately 20% of all mammal species are bats. The order Chiroptera, a Greek-origin name meaning “winged hand” (cheir = hand, pteron = wing), encompasses all bat species.

Bats are distributed throughout most of the planet, except for the poles. They are found on continents as well as on islands far from the mainland. They can live from mountain ranges to desert oases, from tropical regions to boreal ones. They can take refuge in caves, tree hollows, rock crevices, buildings, or amidst the lushness of vegetation. Some even hide among the pebbles along riverbanks.

Unlike birds, bats fly with their hands while birds fly with their arms. They are the only flying mammals. The forelimbs of bats have evolved by elongating fingers and forearms. The bony structures we see in their wings are the fingers of the hand and support a thin, naked membrane called the patagium, which has muscular fibers and many blood vessels. The aerial life of bats has led to various flight-related adaptations. Like birds, bats have a highly developed pectoral musculature that allows them to move their wings and perform flapping flight. However, this musculature requires a rigid bony anchoring structure. This is the sternum, which is also quite developed and in many species has a keel-like shape. The size of bats varies greatly depending on the species.

Bats have other flight adaptations that, while not as evident as wings, are also important for flight. Most species only have one offspring, a characteristic that allows greater maneuverability for gestating females, thereby increasing the probability of survival.

The seasonal movements of bats can vary greatly from one species to another or even among populations of the same species. Some can make long seasonal migrations that in some cases exceed thousands of kilometers. This is the case of the lesser noctule bat (Nyctalus leisleri), very abundant in the forests of the Pyrenees.

In Catalonia, the most well-known migrations are those of the Schreiber’s bat (Miniopterus schreibersii), a species that flies relatively quickly and can make seasonal movements exceeding 300 km.

Another interesting aspect of bat biology is their longevity. It is longer compared to what would be expected based on their body size.

Bats exploit a wide range of food resources, from those that eat fruit to the mythical vampires. There are bats that eat frogs, birds, fish, small reptiles, scorpions, or even carrion. Another type of diet is nectarivorous, which corresponds to feeding on the nectar and pollen of flowers. Bats with this dietary regime contribute to pollinating a large number of plants.

There are even plant species whose pollination is highly specialized and depend on certain bat species. However, the majority of species (70%) of bats eat insects.

They have the ability to emit ultrasound for orientation, communication among themselves, and also for locating and hunting prey

The calls emitted for communication among bats, also known as social calls, are used between mother and offspring in breeding colonies, for mating, for marking territory, or for defense when they feel threatened. The process by which animals locate objects they cannot see or touch through the emission of acoustic signals and the analysis of their echoes is called echolocation. Ultrasound calls are produced by the vocal cords. The ultrasound emitted undergoes reflection when it encounters obstacles, and the echoes are captured again by the emitting bats. Echolocation allows measuring the distance between the emitter and the obstacle, but it also enables calculating the relative speed of the prey, since normally neither the bat nor the prey are stationary. Bats also use echolocation to receive information about the shape, size, and texture of the surface of the object in front of them.

Contrary to popular belief, bats are not blind. They have eyes that allow them, when there is sufficient light, to perceive the world in black and white.

Tracking 7 species of bats

One of the novelties of this new LIFE compared to the previous one is the study of some bat species. The studied bats are insectivores that feed on large quantities of insects and usually hunt around ponds.

The project includes tracking 7 species of bats: the Barbastelle bat (Barbastella barbastellus), the Greater mouse-eared bat (Myotis myotis), the Alpine long-eared bat (Plecotus macrobullaris) present in the Pyrenees and the Alps, and the Lesser horseshoe bat (Rhinolophus hipposideros), the Greater horseshoe bat (Myotis blythii), Bechstein’s bat (Myotis bachsteinii), and the Greater noctule bat (Nyctalus lasiopterus).

Technologies and tools for studying bats

The study of bats is complex and for this reason, it is the most unknown group of mammals that exists. They are difficult animals to observe because they hide in places that are inaccessible or not easily accessible and they fly at night, which makes their observation difficult. Some of the methodologies used to study them are:

• Bat captures
• Shelter boxes
• Shelter monitoring
• Listening stations with ultrasonic detectors
• Radio tracking

In the case of the LIFE project, the study of bats is carried out through the installation of ultrasonic recording devices emitted by bats and the installation of networks that allow specific identification of individuals, provide data on the biological cycle, and allow the collection of feces for analysis of their feeding and health status.

Thanks to ultrasonic recording devices, the activity of bats and the species that frequent ponds can be known. Their excrement allows us to know what they eat.

They have an important ecological role

Bats provide significant ecosystem services: they pollinate plants, act as seed dispersers, and help control insect populations – a bat can consume up to 3000 insects per night – making them natural pest controllers in agricultural and forest environments. They are major consumers of mosquitoes and therefore help us keep these insects, which are major disease vectors such as malaria or dengue, in check.

One of the interesting tasks of the project is to compare the presence of bats in ponds with fish and ponds without fish. When there are fish in a pond, the entire biodiversity of the pond is affected and modified. The study aims to determine if this mentioned impact on biodiversity also affects the structure of the bat community, that is, the abundance and diversity of bats.

Fonts:

• Serra-Cobo J, López-Roig M, Bayer X, Amengual-Pieras B i Guasch F. 2008. Els ratpenats: ciència i mite. Publicacions i Edicions de la Universitat de Barcelona.
• Serra-Cobo J, López-Roig i Bayer X. 2015. El tresor ecològic de les mines de Can Palomeres: els ratpenats. Publicacions de l’Ajuntament de Malgrat de Mar.
• Serra-Cobo J, Sanz V i Martínez-Rica JP. 1998. Migratory movements of Miniopterus schreibersii in the north-east of Spain. Acta Theriologica, 43(3): 271-283.
• https://secemu.org
• Guia de camp. Els ratpenats de Catalunya
• https://www.batmonitoring.org/v0/CAT/coneguem/coneguem.php