Despite the fact that bats are active after sunset, they rely on the sun as their most trusted source of navigation. Researchers from the Max Planck Institute for Ornithology found that the greater mouse-eared bat orients itself with the help of the earth's magnetic field at night and calibrates this compass to the sun's position at sunset (published online in Proceedings of the National Academy of Science, PNAS, March 29th, 2010)
Greater Mouse-Eared Bat (Myotis myotis)
Image: Stefan Greif
Greater Mouse-Eared Bat (Myotis myotis)
Image: Dietmar Nill
Since the 1940s it has been known that bats use echolocation calls for orientation at close range. Some bats, however, fly 20 km and more away from their roost every night to search for prey. Summer and winter roosts are often over 50 km apart and some species migrate even up to 1000 km each year across Europe. Recent evidence has shown that bats utilise the Earth's magnetic field for orientation on longer journeys. Scientists of the Max Planck Institute for Ornithology have now confirmed this finding after conducting research on the ability of greater mouse-eared bats to find their way home at night after manipulations of the magnetic field at sunset.
First, Richard Holland, Ivailo Borissov and Björn Siemers wanted to discover if bats are able to orient themselves at an unknown location. To do so, they captured bats and released them 25 km from their roost cave. They followed their flights with the help of small radio transmitters. Already at 1-3 km distance, most bats were heading home in the direction of their cave. "I was quite sceptical that this first part of the experiment would work," says Björn Siemers. "Therefore I was very impressed that the fastest bats arrived back in their cave only two hours after release". The precise question the researchers wanted to answer was: is this ability for orientation in unknown territory somehow related to perception of the magnetic field? And, further to this, do the bats then calibrate their magnetic compass to the sun like migrating birds?
The three researchers altered the direction of the magnetic field from north to east for half of the bats during sunset with the help of a device called a Helmholtz coil. And in contrast to the control group, these bats flew about 90 degrees east instead of south to their home cave. The decisive last part of the experiment was to repeat the procedure at night. Again the magnetic field of half of the bats was turned from north to east, but only after all signs of sunset had vanished from the sky. In this case the bats with an altered magnetic field flew in the same direction as the control bats. "The manipulation of the magnetic field was only effective in combination with the sunset", says Richard Holland. "Greater mouse-eared bats used the position of the sun at sunset as the most reliable indication of direction, and calibrated the magnetic field with it to use it as a compass later that night". For the bats, sunset means west, regardless to what their actual magnetic field is telling them. Due to iron deposits in the local earths crust, the magnetic field is known to vary unpredictably. It seems therefore that the animals find the sun to be a more trustworthy source for direction. This result is remarkable, given that this species usually emerges from their caves after sunset. "After the bats became active, we were able to see where the sun had disappeared even an hour after sunset", says Björn Siemers. This 'glow' seemed to be sufficient for the bats orientation. [SP]Original work:
Proceedings of the National Academy of Sciences (PNAS). Published online March 29th, 2010
Dr. Sabine Spehn | Max-Planck-Institut
At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History
New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy