Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Straw-coloured fruit bats: Ecosystem service providers and record-breaking flyers

15.10.2015

When searching for food, African straw-coloured fruit bats cover greater distances than any other bat species studied to date

African straw-coloured fruit bats fulfil important ecosystem functions by dispersing seeds and pollen during their flights. Researchers from the Max Planck Institute for Ornithology in Radolfzell together with colleagues from Ghana fitted African straw-coloured fruit bats (Eidolon helvum) with GPS-loggers to reveal the routes flown by the animals.


Colony of straw-coloured fruit bats (Eidolon helvum) roosting in Accra, Ghana.

© MPI f. Ornithology/ J. Fahr


Individual flight routes of straw-coloured fruit bats during he dry season (grey: urban area of Accra, green: tree density).

© MPI f. Ornithology/ J. Fahr

Travel distances differed substantially according to season: during the dry season they covered up to 180 kilometres per night, while distances flown in the wet season was just one-third of this or less. This could be related to variations in population size during these periods.

While the observed colony only consisted of a few thousand individuals during the wet season, in the dry season its population increased to over 100,000 bats. The more bats there are, the greater the competition food, and the further the animals have to fly to find sufficient food supplies.

Every evening as night falls in Accra, a colony of African straw-coloured fruit comes to life. “At first, just a few animals become agitated. Then more and more of them follow suit and a gigantic natural spectacle unfolds,” enthuses Jakob Fahr, who headed the study. “You can almost set your watch by them.”

The animals spend the days hanging upside down in the crowns of old mahogany trees. As soon as the sun sets, the time for resting is over and the entire colony embarks on its search for food: “When the fruit bats take off, the sky darkens” says Fahr. Every evening during the dry season, around 150,000 animals with a wingspan of up to 80 centimetres head off in all directions. They search for fruit and nectar before returning to their day roosts the following morning.

Straw-coloured fruit bats are among the most common bat species found on the African continent. These mammals live in colonies and exhibit pronounced migratory behaviour – presumably due to the seasonal variations in food availability: depending on the dry or wet season, they gather in groups of up to several hundred thousand individuals – as is the case in the Accra colony. At the beginning of the wet season, most bats leave Accra and migrate to northern savannas, leaving just a few thousand individuals behind.

The Radolfzell-based scientists wanted to establish whether the seasonal size variation of the Accra colony has an impact on the bats’ nocturnal foraging behaviour. They hypothesized that a larger colony should lead to longer commuting flights to find sufficient amounts of food.

The scientists were particularly interested in the bats’ nocturnal wanderings because they disperse seeds and pollen in the process and thus fulfil important roles in the continent’s ecosystems. Fahr also refers to the animals in this context as the “Gardeners of the African Forests”. The extent of foraging areas in which the fruit bats perform this “gardening” and how the size of the colony affects it were largely unknown up to now.

The researchers started by catching several individuals using nets and attaching small GPS-loggers to them. “The battery-operated transmitters last up to seven days,” explains Fahr. “At some point, they simply fall off and, if we’re lucky, we’re able to use them again.”

The transmitters record both the routes covered by the bats and acceleration data. This gave the scientists an intimate picture of flight movements between the bats’ roosting and feeding locations. To access the information, the scientists had to visit the colony during the day and collect the recorded data using a receiver. Then the “treasure hunt”, as Fahr calls it, began. Travelling by taxi, the researchers looked for the fruit bat’s feeding sites by following the GPS-coordinates visualized with Google Earth. “Usually you find discarded food remains under the trees”, explains Fahr. This enabled Fahr and his colleagues to identify what the animals had actually eaten – in addition to the flight routes.

Their analyses showed that the enormous colony mainly feeds on nectar during the dry season when the bats commute up to 180 kilometres each night. In contrast, during the wet season, when the colony shrinks to a few thousand individuals, the bats feed almost exclusively on nearby fruits. The average distance travelled falls to around one-third of that covered during the dry season.

The study suggests that African straw-coloured fruit bats compete less for food during the wet season, and for this reason do not fly such long distances during this period. “The fruit available during the dry season may not be sufficient to feed all of the animals. It is also possible that they need certain nutrients during this season and for this reason prefer to feed on nectar.” To clarify this, the scientists would have to quantify food availability in detail.

ny case, the fruit bats provide crucial ecosystem services: their one-way flight routes of up to 90 kilometres make them record-holders among all bat species. During their search for food, they disperse plant seeds across astonishingly large areas. They fly over areas that have been deforested and fragmented by human land use. Moreover, many other seed dispersers have been decimated in many areas due to hunting. “For this reason, fruit bats should not be primarily associated with infectious diseases. They fulfil important ecological roles, without which Africa’s ecosystems would disappear,” says Fahr.


Contact

Dr. Jakob Fahr
Max Planck Institute for Ornithology (Radolfzell), Radolfzell
Phone: +49 531 3912391

Email: jfahr@orn.mpg.de

Mobil: +49 178-14 37 687


Original publication
Jakob Fahr, Michael Abedi-Lartey, Thomas Esch, Miriam Machwitz, Richard Suu-Ire, Martin Wikelski, Dina K. N. Dechmann

Pronounced seasonal changes in the movement ecology of a highly gregarious central-place forager, the African straw-coloured fruit bat (Eidolon helvum).

PLOS One; 14 October, 2015

Source

Dr. Jakob Fahr | Max Planck Institute for Ornithology (Radolfzell), Radolfzell
Further information:
https://www.mpg.de/9676068/palm-fruit-bats-ecosystems

Further reports about: Ecosystem Max Planck Institute Ornithology animals dry season fruit bats;

More articles from Life Sciences:

nachricht Microbes can grow on nitric oxide (NO)
18.03.2019 | Max-Planck-Institut für Marine Mikrobiologie

nachricht Novel methods for analyzing neural circuits for innate behaviors in insects
15.03.2019 | Kanazawa University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Revealing the secret of the vacuum for the first time

New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum

For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...

Im Focus: Sussex scientists one step closer to a clock that could replace GPS and Galileo

Physicists in the EPic Lab at University of Sussex make crucial development in global race to develop a portable atomic clock

Scientists in the Emergent Photonics Lab (EPic Lab) at the University of Sussex have made a breakthrough to a crucial element of an atomic clock - devices...

Im Focus: Sensing shakes

A new way to sense earthquakes could help improve early warning systems

Every year earthquakes worldwide claim hundreds or even thousands of lives. Forewarning allows people to head for safety and a matter of seconds could spell...

Im Focus: A thermo-sensor for magnetic bits

New concept for energy-efficient data processing technology

Scientists of the Department of Physics at the University of Hamburg, Germany, detected the magnetic states of atoms on a surface using only heat. The...

Im Focus: The moiré patterns of three layers change the electronic properties of graphene

Combining an atomically thin graphene and a boron nitride layer at a slightly rotated angle changes their electrical properties. Physicists at the University of Basel have now shown for the first time the combination with a third layer can result in new material properties also in a three-layer sandwich of carbon and boron nitride. This significantly increases the number of potential synthetic materials, report the researchers in the scientific journal Nano Letters.

Last year, researchers in the US caused a big stir when they showed that rotating two stacked graphene layers by a “magical” angle of 1.1 degrees turns...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

How heavy elements come about in the universe

18.03.2019 | Physics and Astronomy

Robot arms with the flexibility of an elephant’s trunk

18.03.2019 | Power and Electrical Engineering

Microbes can grow on nitric oxide (NO)

18.03.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>