Egyptian fruit bat

Rousettus aegyptiacus

 

Rousettus Aegyptiacus, also known as the Egyptian fruit bat is a member if the family Pteropidae.  The Egyptian Fruit bat is a mega bat and like other mega bats it is found only in the Old World.  R. aegyptiacus is one of the most common of the Rousset bats.  Rousset bats are the only genus of mega bats that use a form of echolocation.

 

TAXONOMY

The taxonomy of the Egyptian fruit bat puts it in the subgenus Rousettus.  R. aegyptiacus is the only bat in this subgenus.  The classification has its basis in the type of hair that is present or not present on adult males.  These stiff and course sticky hairs were found in other genera but not in the aegyptiacus species (Rosevear 80).  There have been other much more recent studies of the taxonomy of rousettus aegyptiacus.  The August 1997 study of Javier Juste B., Carlos Ibanez and Annie Machardom analyzed 82 different specimens of four different African Fruit bats.  One of the four species that was analyzed was R. aegyptiacus.  By analyzing the blood from the specimens the team of researchers was able to conclude that Rousettus bats are not as closely related to the other genus as was originally thought.  This led them to believe that the Roussets were actually more recent additions to Africa¹s wildlife (J. Javier B. et al. 776).

 

PHYSICAL CHARACTERISTICS

As far as bats go the Egyptian fruit bat is rather large.  It weighs from 81-171 grams, has a wingspan of around 2 feet, and a body length of 5 ¼ to 6 ¼ inches (Nowak 52).  The exact color schemes of the bats vary with their location (Rosevear 81) but they are usually a dark brown or reddish brown on the top of their bodies and a paler shade on the underside.  As discussed in the last paragraph these bats also lack the tuft of hair around their neck that some of the other genus have.  Unlike other bats, R. aegyptiacus has a small tail that is not found in the eppaulated fruit bats (Taylor 58).  These bats do not have nose leaves or any other unusual facial characteristic.  In fact in the face they look more like a fox than a bat.  This is why they are sometimes referred to as flying foxes.

 

RANGE

As with other mega bats the Egyptian Fruit bat is found only in the old world.  It ranges from Southern and Western Africa to the Middle East and even some of the Mediterranean countries (Taylor 58).  In a study conducted in 2002 entitled, ³The Bats of the Eastern Black Sea Region in Turkey² it was recorded that Rousettus aegyptiacus reach some of the farthest north regions in Anatolia.

 

REPRODUCTION

Rousettus aegyptiacus has a relatively short reproductive cycle.  It has a 2-3 uninterrupted oestrus cycles (Altringham 136-137).  This rather high reproductive potential may actually be to their advantage.  In Israel they were the target of a widespread chemical extermination.  The bats were thought to be pests and a nuisance to farmers.  The caves that they lived in were sprayed with the poison Lindane.  This widespread fumigation lead to the elimination of some species of micro bats but it had little effect on the Egyptian fruit bat.  It was proposed that the reason for the lack of effect was this higher reproductive rate (Makin, Mendelssohn, 1).

 

HABITAT / HABITS

These bats live in caves, old tomes dark crevices and other similar surroundings.  They are able to live in darkness unlike other mega bats because of their primitive yet effective form of echolocation. This will be discussed in more detail later in the species account.  The bats seem to choose the site of their homes more upon the existence of a suitable cave then location of food.  They have been known to travel 15 km in search of food.  They have been found in the tropical rainforests of Africa as well as the dry desert regions (Rosevear 79).  At around dusk the bats leave their caves and begin to search for fruit.  As the bats move from tree to tree and feed on fruit they pick up pollen and carry it from one tree to another and pollinate the trees.  It actually plays an economically important role in the Old World by pollinating the Baobab tree (Nowak 25).  Because the bats are nocturnal they rarely are out in the sunlight and therefore do not develop any vitamin D.  Scientists have done experiments to determine if they have a heightened metabolism for the production of vitamin D to make up for their natural deficiency (Buffenstein et al., 6)

 

CONSERVATION

These bats are not endangered and are actually quite common in Africa and the Middle East.  At one point they were so abundant in Israel that they were becoming a nuisance and the government tried to limit their numbers.  This was unsuccessful but the numbers did eventually drop off but this was thought to be due to overpopulation.  Although the bats are still numerous conservation groups do exist and attempt to limit any similar events in the future (Makin, Mendelssohn 1).

 

ECHOLOCATION

One of the most fascinating things about Rousettus aegyptiacus is its ability to echolocate.  It uses a clicking sound that it produces in its mouth to emit a noise that it can then listen to the echo and interpret the location of objects in its surroundings.  Rousetts are the only type of mega bat to use echolocation (Heffner, Heffner, Koay 2).  Many studies have been performed on the Egyptian fruit bat to try and learn more about this unique characteristic.  Using an acoustic chamber and trained bats, scientists were able to study the level of hearing in R. aegyptiacus.  The bats were trained to lick a syringe full of food and to break contact with the syringe when a tone was played.  Immediately after the tone was played a small shock was transmitted through the syringe.  This shock would serve as incentive for the bats to listen for the warning tone.  Using this system the scientists were able to determine the limits of the bats hearing.  Through experimentation it was determined that the bats could hear lower frequency sounds better than micro bats, but they couldn¹t hear high frequency sounds as well (Heffner, Heffner, Koay 10)  This makes sense because the clicks that the Egyptian fruit bat produces are much lower frequency than the high frequency sounds that the micro bats echolocate with.  The bats hearing seems to be best suited to recognize its own call.  In a study conducted by the same group of scientists in 1999 they used a similar setup with a couple different aspects in order to test the sound localization capabilities of R. aegyptiacus.  In this experiment the bat was again inside an acoustic chamber and again fed from a metal syringe.  Only this time the warning tone was played from one of several speakers located around the chamber.  In this manner the scientists were able to test the ability of the bat to recognize the direction from which a sound was received.  From the results of their experiments the scientists concluded that the bats had sufficient hearing to determine the location of objects to the point that their primitive echolocation would still be very useful (Heffner, Heffner, Koay 12).

 

 

Works Cited

Albayrak, Irfan. "The Bats of the Eastern Black Sea Region in Turkey (Mammalia: Chiroptera)." Turkish Journal of Zoology  (2002). 21 Feb. 2004 <http://ebsco.com>.

Altringham, John D. Bats Biology and Behavior. 3rd ed. Oxford: Oxford UP, 1999. 136-137.

Bats of Southern Africa. Scottsville, South Africa: University of Natal P, 2000. 58-60.

Beffenstein, Rochelle , et al. "Vitamin D metabolism in a Fruvigorous NOcturnal Mammal, The Egyptian Fruit Bat (Rousettus aegyptiacus)." General and Comparative Endocrinology  (2003). 21 Feb. 2004 <http://www.sciencedirect.com>.

B., Javier J., Carlos Ibanez, and Annie Machordom. "Evolutionary Relationships Among the African Fruit Bats: Rousettus Egyptiacus, R. Angolensis, and Myonycteris." Journal of Mammology  (1997). 

Heffner, H. E., R. S. Heffner, and G. Koay. "Hearing in a Megachiropteran Fruit Bat (Rousettus aegyptiacus)." Journal of comparative Psychology  (1998). 21 Feb. 2004 <http://www.weblinks2.epnet.com>.

Heffner, H. E., R. S. Heffner, and G. Koay. "Sound Localization in an Old World Fruit Bat (Rousettus aegyptiacus)." Journal of Comparitive Psychology  (1999). 21 Feb. 2004 <http://www.weblinks.epnet.com>.

Makin, David, and Dr. H. Mendelssohn. "Insectivorious Bats Victims of Isreali Campaign." BATS  (1985). 21 Feb. 2004 <http://www.batcon.org/batsmag/v2n4-1.html>.

Nowak, Ronald  M. Walker's Bats of the World. Baltimore: Johns Hopkins UP, 1994. 25.

Rosevear, D. R. The Bats of West Africa. Margate: Eyre and Spttieswoode Limited, 1965. 76-84.

 

 

Lloyd Hocking

HONR 278c

February 22, 2004