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
New photocatalyst speeds up the conversion of carbon dioxide into chemical resources
29.05.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)
Copper hydroxide nanoparticles provide protection against toxic oxygen radicals in cigarette smoke
29.05.2017 | Johannes Gutenberg-Universität Mainz
The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.
The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
29.05.2017 | Earth Sciences
29.05.2017 | Life Sciences
29.05.2017 | Physics and Astronomy