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Dragoș Ștefan Măntoiu BATS

Bats are the only mammals able to sustain active flight. Over the course of their evolution, which stretched for more

Dragoș Ștefan Măntoiu


General information on bats
Bats are the only mammals able to sustain active flight. Over the course of their evolution, which stretched for more than 50 million years, they have remained largely unchanged due to some very good adaptation capabilities in response to the environment. Bats populate most of the Earth’s biomes, except for the Arctic, occupying various ecological niches such as pollinators in tropical and equatorial areas, frugivores, nectarivores, carnivores, hematophagous and most commonly insectivores. There are over 1300 bat species in the world, out of which 45 are in Europe and 32 in Romania. Due to lack of food during the winter, temperate insectivorous bats use an adaptation called hibernation to survive in the cold season. They can lower their body temperature to that of the surrounding environment, which is usually between 3 and 10°C. During this time, their heart may reach one or two beats per minute. This adaptation allows their body to consume a very low quantity of energy, ensuring successful passage over the scarce food period, also increasing their longevity and their ability to fight various diseases. Bats give birth to one or two pups a year which are fed with milk between June and August. Most of the species from the temperate climate areas migrate between summer and winter shelters, reaching distances of over 2,000 km. Some of the bat migration routes cross over seas, but their pathways and orientation techniques that allow them to navigate in such conditions are still largely unknown. Generally, colonies return to the same shelters, learning from generation to generation which shelters are safe and climate-friendly. From all of the bat species present in Romania, only 5% roost in caves, the rest being largely arboreal or seeking shelter in rock crevices or fissures. All species of bats in Romania and the European Union are protected by law, because their populations have suffered a strong decline. Given the natural habitat loss and fragmentation, part of the bat species migrated to anthropogenic areas to carry out their biological cycles.

The importance of bats in the temperate climates
Bats eat a huge quantity of insects. A stable population of bats can significantly reduce the number of insects potentially harmful to humans, with beneficial effects in agriculture and the anthropic environments. The best example of ecological engineering by chance is the city of Austin, Texas, U.S.A., where a colony of over one million specimens of Tadarida brasiliensis found refuge under a bridge. The hunting ground of the colony is the city, and the locals have abandoned the use of insecticides because the bats have been able to significantly reduce the number of harmful insects in the environment. Apart from this, the community also sustains ecological and educational tourism, offering the opportunity to learn about the bats’ lifestyle as the animals leave the roost. The natural control of harmful insects with the help of the bats is preferable to insecticides, because the method can lower the amount of toxic substances released into the ecosystem. The compounds of these substances could bioaccumulate in the food chain, affecting the protected animal populations and wild plants, but also humans.

The Bats of Bucharest
There are 10 bat species in Bucharest, some of which are permanent residents, but most of them are migrants, traveling to northern Ukraine or central Russia to give birth (Nyctalus noctula). In the summer, species such as Pipistrellus pipistrelus, Pipistrellus kuhlii, Pipsitrellus nathusii, Pipistrellus pygmaeus or Eptesicus serotinus form maternity colonies in the cracks of residential blocks of flats or in the houses’ lofts. During the cold season, the migratory species return to the city to hibernate alongside their pups, which survived the migration (Nyctalus noctula, Nyctalus leisleri, Vespertilio murinus). Occasionally, the water bat is observed (Myotis daubentonii) in the northern area of the city, as well as a very rare species (Nyctalus lasiopterus) in the southwestern marginal forests.

Bats’ roosts in Bucharest range from old lighting poles, to subterranean subway networks, abandoned houses, cracks and joints of residential blocks of flats, old trees’ hollows, old forts and batteries surrounding the city, shutters of old houses, spaces between drainage pipes and building walls, churches’ towers without meshes or windows, the roof and the interior of public institutions, often in those built of stone blocks (the Free Press House, the Parliament), the office buildings’ ventilation system, the houses’ loft, and also the spaces between the thermal insulation of the buildings and the wall, with access via the utility holes (air conditioning, stove, etc.).

Because of the myths that surround these species (like they might plunge in someone’s hair or suck someone’s blood, or chew the wafer, etc.), taken from both national and international folklore, human-bat interactions don’t always end well. This is due to the bats’ nocturnal lifestyle, which is associated with superstitions. Most of the time, owners or administrators of buildings with bat roosts consider them pests, without taking into account the fact that they are protected by law and could bring certain benefits. The real inconveniences associated with the presence of bats near a working or living space are related to the noise they can produce when they move through the thermal insulation and the odor generated by the colony. These animals are insectivorous, so they will not chew the insulation or other materials, because they have very fragile teeth, unlike the rodents which they are so often confused with. On the other hand, the noise occurs only when their feet are trying to catch rough surfaces. Another problem might be the biological danger. Bats are animals that can carry various zoonosis. In Romania, there have been no recorded cases of rabies transmitted from bats to humans, and the chances that an animal might be infected are very small (the virus is more frequently found within a small number of species, which are very shy), but it is preferable that domestic animals or children walking below the colony to not come into contact with the guano or potentially dead individuals. This can be avoided by placing a small plastic shelf underneath the colony and regularly cleaning it. Collected bat guano can be later used as natural fertilizer.

One of the most common causes of the bat colonies’ extermination in Bucharest is the thermal envelope of the residential buildings. Workers often block the animals in the building cracks, without giving them the chance to escape. There are situations when bats are killed directly, by spraying harmful substances inside the cracks or by being impaled with long and sharp objects. Bat colonies can be heavily affected by the building renovations if the works are done while they hibernate. During this period, bats are inactive and they cannot fly away from the roost (often workers are not even aware of the bats’ presence). During maternity (June to August), if the colonies are disturbed, mothers can abandon their pups in the roost, in order to save themselves (the self-conscious instinct), skipping therefore a generation and increasing the risk of local colony extinction. Moreover, if the cutting of old trees with scabs is done without checking whether they are populated by bats (or nesting birds), the risk is similar. Also, the excessive use of insecticides in city parks considerably reduces the life expectancy of bats and it might cause hormonal disturbances that can affect their reproductive system.
To alleviate this human – bats conflict, Wilderness Research and Conservation Association (WRC) through the Bat’s Protection and Research Program (Facebook – Protection and Study of Bats), conducted in partnership with the Visul Luanei Foundation, performs safe relocation actions for both bats and humans. The program also provides round the clock consultancy in case of bat – human interaction. The Association’s volunteers respond to calls regarding wounded animals and transport them to the «Visul Luanei» Animal Rehabilitation Centre (L’ARC), where wildlife veterinarians intervene. In case of colony relocation during the cold season, the rehabilitation center takes the animals into protective care and performs regular feeding to ensure the colony’s survival. Hand feeding a bat is a lengthy process, waking up a colony from hibernation causes allot of stress for the animals. For this reason, volunteers are called upon to ensure a fast and efficient feeding process. Winter relocation causes bats to consume a lot of energy, and premature release can lead to a high mortality rate, so constant feeding sessions and special treatments need to be assured, in order to reduce the impact of the relocation. The educational programs and actions for the improvement of bats conservation status in the urban environment are carried out in the frame of the Urban Bats Project (Liliecii din Mediul Urban), initiated by Wilderness Research and Conservation Association and supported by the IKEA Fund for the Urban Environment, funded by IKEA Romania and managed by the Bucharest Community Foundation (Fundaţia Comunitară Bucureşti).

During the last 3 years, hibernating colonies of bats were treated, fed and safely relocated, with a maximum number of 497 individuals per season. The release of the animals is done in a controlled state, choosing a safe green urban area, where no insecticides are being administered, such as the Botanical Garden of Bucharest. In the case of the very large colonies, bats are released into Comana Natural Park or Văcăreşti Natural Park. Extracting a colony of bats from a building subjected to thermal rehabilitation is quite simple if done during periods when the integrity of the colony is not threatened (April – May and September – October). The biological discharge is carried out by chiropterologists. They observe the activity of the animals for at least 3 days, during which the weather conditions give bats the chance to feed: no rain and temperatures preferably over 20°C. The specialists identify the area where the animals leave the building, then cover it with a flap made of lightweight and flexible materials. Animals can push the flap to get out, but cannot access the shelter anymore. Once the specialists confirm that the extraction was a success, the enveloping process can begin, but the roost should be closed off during the day. There have been cases when the owners wanted to save animals at all costs, being aware of the benefits of having a colony close to their home. The enveloping was made with an access channel for bats, and they are still active in the shelter even after the completion of the rehabilitation works.

Special roosts for bats were built and purchased to provide alternative shelters during the warm season, in order to reduce the human – animal conflict. They were installed in the Botanical Garden in Bucharest, the «Grigore Antipa» National Museum of Natural History courtyard (MNINGA) and the Comana Natural Park. The Urban Bats Project aims to mount 30 shelters in 2017 to increase the degree of isolation from humans by maintaining bat populations in areas of major importance for insect consumption: in the green urban areas of the city which preferably contain lakes and ponds. The success of these artificial roosts depends on the microclimate created inside and also the isolation degree from predators. They will not be used by bats if birds can nest inside. Typically, shelters are mounted at heights greater than 6 meters, on a tree or a building façade with a south-east exposure, in order to capture the morning sun. Choosing a good roost site is hard, because it also needs to have a clear access path for bats, with no branches or cables in the way.

The roost should have a landing zone, a narrow area to exclude predators and one or more chambers where the bats could give birth or spend the summer safely. The degree of colonization is generally low, and the signs of success are usually seen after 3 years after the roosts were mounted. If the roost is not used, it could be relocated to save resources. Usually, the roosts are made out of wood with a low odor degree. The exterior is lacquered with nontoxic water based substances, in order to protect it from weather conditions. Afterwards it is painted black with water based paint, in order to attract the morning warmth. Only non-toxic products are used to not affect the animals inside. The interior has to include small and narrow spaces, and the supporting platform has to be carved or scratched forming a series of parallel cuts. These offer the animals the chance to cling on to the roost when landing and climb up to safety. A certain producer in Romania provides this kind of shelters (www.hortieco.ro). The most successful models have a 30% rate of colonization and are made of a composite material, called woodcrete (cement and wood wool). This material is placed in forms that are specially designed to confer suitable bats habitats, similar to the building cracks or trees’ hollows. Currently, there are no internal producers, yet there are 2 such shelters installed by WRC in the MNINGA interior garden. Special bat roosts could be incorporated in the buildings’ construction. Roof tiles with small holes could be used to allow the bats’ access or an exterior roof‘s structure could be modified to include bricks with special holes, able to accommodate small colonies.

Bats research methods in urban environment
Information collected in the Bats’ Protection and Research Program (Protecţia şi Studiul Liliecilor) offered the needed starting point for the cartography of the urban colonies, based on data provided by citizens and also research based on ultrasound detectors. These devices transform the sounds of bats, from very high frequencies into audible sounds within the human specter; moreover, their recordings can offer researchers details about what species are present in the site and their current activity (hunting, reproduction, transit sounds, sounds of babies and despair sounds in case of a predator’s threat). In the warm season of 2017, WRC conducts workshops in the Văcăreşti Natural Park, in order to educate the public regarding the echolocation capabilities of bats: Bats’ Bioacoustics in the Urban Environment – an event organized within the Urban Bats Project.

Currently, there are multiple roosts known in the Northern part of the city, due to the proximity to the wet zones which are optimal feeding grounds. The area also has lower yearly temperature fluctuations compared to the heat island effect which is felt more to the center of the city.

These projects aim to reduce the negative impact generated by humans on bat populations in urban areas, to enhance the animals’ capacity to consume insects, improving the quality of life in the city, to increase the public awareness on bats, informing people of the benefits conferred by these animals, and also to enhance the collaboration with local authorities in finding and adopting friendly techniques for green urban spaces and residential buildings enveloping management and practices.

Review overview