Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fruit Bats Navigate with Internal Maps

16.08.2011
Israeli scientists fitted fruit bats with the world’s smallest GPS devices
to track their homing flight after relocation far away

GPS technology can make our travels easier and more efficient. But for many animals, the ability to successfully navigate a landscape is not just a matter of convenience – their very survival depends on it.

Egyptian fruit bats, for instance, fly dozens of kilometers each night to feed on specific fruit trees, making the return trip the same night. To understand how the bats locate individual trees night after night, scientists attached tiny GPS devices to the bats in the first-ever comprehensive GPS-based field study of mammal navigation.

The results of this study showed that the bats carry around an internal, cognitive map of their home range, based on visual landmarks, such as lights or hills, but the study also suggests an additional,, large-scale navigational mechanism. The study, which appears August 15 in the Proceedings of the National Academy of Sciences (PNAS), reveals for the first time how free-ranging mammals find their way around their natural environment.

Many researchers have investigated the navigational skills of other creatures – birds, fish, insects, lobsters, turtles, etc. – but studies of mammalian navigation have been confined to the laboratory. Unfortunately, lab studies cannot duplicate the large, complex landscapes an animal must navigate in the natural world.

The new GPS-based method gives researchers the best of both worlds. This new approach to studying bat navigation was developed by a group of researchers from several institutions and disciplines: ecologists studying movements of animals in the wild: Ph.D. student Asaf Tsoar from the Movement Ecology Lab and his supervisor Prof. Ran Nathan from the Hebrew University of Jerusalem; a neurobiologist studying the neural basis of navigation: Dr. Nachum Ulanovsky of the Weizmann Institute, in collaboration with Giacomo Dell'Omo of Ornis Italica, Italy, and Alexei Vyssotski of ETH Zurich, Switzerland.

In this collaborative effort, the team developed miniaturized GPS devices – each weighing around 10 grams and containing tiny GPS receivers, in addition to a memory logger and battery. They used the devices to track the movements of Egyptian fruit bats (Rousettus aegyptiacus) over several consecutive nights.

At first, the researchers collected data as the bats took flight each night from a cave near the Israeli city of Beit Shemesh. These bats flew in a straight line at speeds of 40 km an hour and more and at elevations of hundreds of meters to trees that were about 12 to 25 km from their cave.

They went to the same trees, night after night, even bypassing apparently identical trees that were nearer to home. The data showed that bats’ navigational abilities rival those of homing pigeons.

The fact that the bats bypassed similar fruit trees to get to their favorite feeding site ruled out smell as their main navigational aid, while an analysis of the data suggested that the bats were not simply “beaconing” on any visual or other individual cue.

To investigate further, the scientists took some of the bats to a new area in the desert, 44 kilometers south of their normal range. Some bats were released at dusk; others were fed in the new area and released just before dawn. Those released first had no trouble navigating to their favorite fruit trees, returning straight back to their caves afterward. Those who were fed first simply made a beeline back to the cave once they were released.

Based on a spatial model analysis, and after discussions with pilots, it appeared, though, that the bats could have seen some familiar visual landmarks – hills or the lights of human settlements – from this release site near Beersheba in southern Israel.

To prevent the bats from using visual landmarks to guide them, the researchers removed the bats even further south, to a natural depression that limited their field of vision: the Large Crater, located some 84 km south of their cave. Here, some of the bats were released from a hilltop at the edge of the crater and others were let go at the crater’s bottom.

Despite the distance, those flying from the hilltop oriented themselves right away and flew back to the cave. The bats inside the crater, however, appeared disoriented, wandering for quite a while before finding their way out of the crater and back to the cave. This confirmed the idea that bats use visual information from a “bird’s eye view” to construct a cognitive map of a wide area. Navigational cues include these distant landmarks, and the scientists believe that the bats most likely compute their own location by employing a form of triangulation based on the different azimuths to known distant landmarks.

Because most of the bats released in the crater, when they finally left, exited to the north (the direction of home), Tsoar, Nathan and Ulanovsky believe that the bats may have an additional, back-up navigational mechanism to help when landmarks are unreliable. This mechanism might involve sensing the magnetic fields or directional odors carried on the sea breeze from the Mediterranean to the Negev Desert.

Although lab experiments based on distances of a meter or two had hinted at the existence of an internal map for navigation, this study is the first to show that such mammals as fruit bats use these maps to find their way around areas 100 km in size.

For further information:
Jerry Barach, Dept. of Media Relations, the Hebrew University,
Tel: 02-588-2904.
Orit Sulitzeanu, Hebrew University spokesperson, Tel: 054-8820016.

Jerry Barach | Hebrew University of Jerusalem
Further information:
http://www.huji.ac.il

Further reports about: GPS data GPS devices GPS-based bats cognitive map fresh fruit fruit bat fruit trees magnetic field

More articles from Life Sciences:

nachricht The birth of a new protein
20.10.2017 | University of Arizona

nachricht Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>