Tabachka Bat Research Station, Bulgaria

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The Bulgarian landscape holds both rich food and roost supplies for various bat species.

MPIO/Greif

The Tabachka Bat Research Station (TBRS) is the field station of the Sensory Ecology Group, run in cooperation with the Directorate of the Rusenski Lom Nature Park. It is situated in the village of Tabachka in Northern Bulgaria. The goal of the field station is to investigate fundamental questions on the ecology and behavior of bats and at the same time to provide scientific information needed for the conservation management of the local bat populations.

The landscape of the Rusenski Lom area is characterized by about 170 km of carstic river gorges, forest, bush and steppe habitats, small scale self-subsistence farming in the gorges and large scale agriculture on the plateau. More than 600 caves and rocky niches provide natural roosts for bats. At least 23 bats species occur in the area, of which we regularly include 10-15 in our research work.

We study the bats’ behavior and ecology both in the field and at the field station. In the field, we use radio telemetry to discover where bats fly and forage and how they orient on their nightly excursions. We record echolocation calls and conduct playback experiments to see how bats react to other bats’ calls. We study the bats’ diet from feces and by employing stable isotope analysis (in cooperation with Dr. Christian Voigt, IZW Berlin) from tiny hair or small wing tissue samples. With the aid of genetic techniques, we want to learn about population structure and potential hybridization between species (in cooperation with Dr. Emma Teeling, University of Dublin).

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Since the station started in 2007, 22 students and scientists from 10 countries have worked at TBRS.

At the field station, bats can fly freely in two large flight rooms. Infrared sensitive cameras, some of them high speed, and ultrasound recording gear reveal great detail of the bats’ behavior without disturbing them. In the flight rooms, we can set up a pond to investigate how bats find water bodies, a bush to find out how they search for insects in vegetation or an obstacle course to study their flight maneuvers.  

Field studies are currently conducted on the ecophysiology of Rhinolophid bats, a family that is represented by five species in Bulgaria: Rhinolophus ferrumequinum, R. hipposideros, R. mehelyi, R. blasii and R. euryale.

Main scientific findings from our research in Bulgaria:

1) Changes in dietary preferences in animal species play a pivotal role in niche specialization. Using a stable isotope approach, we found that, in Bulgaria, two morphologically almost identical, sympatric sibling bat species (Myotis myotis and Myotis blythii oxygnathus) forage at deviating trophic levels, and, thus may have different downstream effects on ecosystem processes (Siemers et al., 2011).

2) We were interested to know whether animals can discriminate different closely related, sympatric species. Using a habituation-discrimination assay, we showed that horseshoe bats can distinguish conspecific from heterospecific calls and, more astonishingly, even discriminate acoustically between different congeneric, sympatric species (Schuchmann & Siemers, 2010).

3) We found that greater mouse-eared bats (Myotis myotis) can efficiently find their home cave when released from an unfamiliar site at 25 km away – the fastest bat homed in 1.5 h! We demonstrated that these bats, similar to migratory birds, calibrate a magnetic compass with sunset cues by testing their homing response after exposure to an altered magnetic field at and after sunset. Magnetic manipulation at sunset resulted in a counterclockwise shift in orientation compared with controls, consistent with sunset calibration of the magnetic field, whereas magnetic manipulation after sunset resulted in no change in orientation (Holland et al., 2010).

4) At TBRS, we showed how echolocating bats recognize ponds or other water bodies that are crucial for foraging, drinking and orientation. Wild bats of 15 different species perceived any extended, echo-acoustically smooth surface to be water, even in the presence of conflicting information from other sensory modalities. In addition, naive juvenile bats that had never before encountered a water body showed spontaneous drinking responses from smooth plates. This provides the first evidence for innate recognition of a habitat cue in a mammal (Greif & Siemers, 2010).