Rousettus aegyptiacus

Geographic Range

Rousettus aegyptiacus is found throughout Africa south of the Sahara, in Egypt, and on the coastlines of the Arabian Peninsula (Grzimek, 2003). Egyptian rousettes are most common from latitudes 15 degrees north through 37 degrees south. However, they have been found as far as 40 degrees north in southern Turkey. They are also found on each of the Canary Islands, western North Africa, and throughout the Gulf of Guinea (Nogales et al., 2006; Nowak, 1999).

• Biogeographic Regions
• palearctic palearctic
  • native native
• ethiopian ethiopian
  • native native

Habitat

Egyptian rousettes are found throughout Africa’s tropical rain forests, tropical deciduous forests, savanna, and Turkey’s Mediterranean scrub forests. Egyptian rousettes have been found in arid biomes; however, they prefer to remain in habitats that provide forest cover, roosting opportunities, and abundant fruit tree growth (Kwiecinski and Griffiths, 1999).

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• rainforest rainforest
• scrub forest scrub forest

• Other Habitat Features
• caves

Physical Description

Egyptian rousettes are medium sized bats with dorsal pelage ranging from dark brown to medium gray. Ventral pelage in both genders is several shades lighter than dorsal coloration, with a collar of pale yellow or orange fur often seen around the neck. There is no color difference between genders; however, males have well-developed stiff hairs along the throat that are more recognizable than in females (Kwiecinski and Griffiths, 1999). Short fur completely covers the head almost to the end of the muzzle, with the exception of the forehead, where the fur is slightly longer. Ears are around the length of the muzzle, with blunt tips and dark coloration when compared to dorsal pelage. Egyptian fruit bats have large eyes adapted for twilight and night vision. Wing membranes are dark brown with short fur extending to the proximal half of the forearm. A claw is present on both the first and second digits, while all other digits have cartilage. Egyptian rousettes have five toes on both hind limbs, each with claws (Kwiecinski and Griffiths, 1999).

Males are typically larger than females with a total body length ranging from 14 to 19.2 cm, while females range from 12.1 to 16.7 cm. Adults may weigh 80 to 170 g and have a wingspan close to 60 cm. The forearm varies between 85 to 101.9 mm in males and 88.1 to 99 mm in females (Kwiecinski and Griffiths, 1999; Grzimek, 2003).

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Rousettus aegyptiacus is a polygamous species, with biannual breeding seasons. However, instances of monoestry have been recorded at higher latitudes (Baydemir and Albayrak, 2006; Bernard and Cumming, 1997). Egyptian rousettes observed in latitudes south of Egypt have two distinct peak breeding seasons separated by short periods. The first peak breeding season is from spring through summer, the second is fall through winter. Births occur towards the end of each breeding season (Okia, 1987).

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Females give birth to and raise a single pup with each breeding effort, though twins have been recorded occasionally (Korine et al., 1994). Estimated gestation length is 3.5 to 4 months, with synchronized births occurring in breeding colonies (Kwiecinski and Griffiths, 1999; Okia, 1987). Newborn bats are born with deciduous teeth and are altricial - completely naked apart from a thin layer of down along the head and back. Pups are weaned at 6 to 10 weeks with no difference in growth between sexes. Young reach full adult weight and size around 9 months old, about the same time young become independent from their mothers (Kwiecinski and Griffiths, 1999). Sexual maturity is reached on average at 15 months, however, females have been noted to be sexually mature at 5 to 7 months ("Egyptian Fruit Bat", 2006).

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

After birth Egyptian rousette pups are cared for solely by their mothers for around 9 months. They are capable of flying at 63 to 70 days after birth and stay with their mother until they have reached adult weight and size. Once mature, males leave maternity colonies to join bachelor groups, females join maternity colonies (Kwiecinski and Griffiths, 1999).

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

The recorded maximum lifespan of Rousettus aegyptiacus is 22 years in the wild, with a maximum of 25 years in captivity for both males and females. In wild populations, average lifespan is typically 8 to 10 years due to factors such as predation, vitamin D deficiency, calcium-phosphorus imbalance, and osteoproliferation. Longevity in captive bats is also dependent on environmental temperatures and neurological impairment (Kwiecinski and Griffiths, 1999).

Behavior

Egyptian rousettes are found in groups of various sizes, ranging from small colonies of 20 to 40 members to large colonies of 9,000. These colonies prefer to roost during the day in dark, slightly humid environments such as cave systems and ruins, though small colonies have been seen roosting in trees (Grzimek, 2003). During breeding seasons, males and females separate; males forming bachelor groups and females forming maternity colonies. Egyptian rousettes roost in close contact with other members of the colony to reduce the influence of temperature fluctuations. Close contact among members of the colony also allows communication with each other throughout the day during roosting. Egyptian rousettes are more active during the late afternoon and into the night, when grooming is more frequent (Kwiecinski and Griffiths, 1999). Individuals leave the day roost close to sunset each evening to forage, returning before sunrise. During summer months longer daylength delays emergence from the roost, suggesting a circadian rhythm synchronized to light-dark cycles. Due to the change in light intensity, Egyptian rousettes have different patterns of activity between summer and winter seasons. Summer seasons are characterized by longer feeding intervals than winter seasons, despite reduced dark periods and delayed roost emergence (Kwiecinski and Griffiths, 1999).

• Key Behaviors
• troglophilic
• flies
• nocturnal nocturnal
• motile motile
• migratory migratory
• sedentary sedentary
• territorial territorial
• social social
• colonial colonial

Home Range

Home range varies in Rousettus aegyptiacus . This species has been noted to migrate southward in the northern regions of their geographic range and forage great distances away from day roosts. Males appear to defend territories, but their size has not been characterized (Kwiecinski and Griffiths, 1999).

Communication and Perception

Egyptian rousettes are one of 3 members of the Rousettus genus to use both visual orientation and echolocation. Echolocation in this species is produced through a series of crude, short clicks of the tongue against the side of the mouth (Roberts, 1975; Holland et al., 2004). These short, impulsive-paired clicks assist in navigation in the dark. The frequency range is usually 12 to 70 kHz, with click structure and duration most similar to dolphins. This form of echolocation has evolved independently from the echolocation system used by other echolocating bats, such as vespertilionids (Roberts, 1975; Holland et al., 2004; Holland and Waters, 2007).

• Communication Channels
• visual visual
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• echolocation echolocation
• chemical chemical

Food Habits

Egyptian rousettes are frugivores, preferring to eat the pulp and juice of very ripe fruit. They typically take fruit from trees, such as lilac , mulberry , carob , sycamore , fig , and baobob (Kwiecinski and Griffiths, 1999; Korine et al., 1996; Grzimek, 2003). Egyptian rousettes consume 50 to 150% of total body mass in fruit each night. After selecting fruit, Egyptian rousettes take their fruit and roost close to the feeding tree. Only the pulp and juice is consumed; after thorough chewing, the seeds are spit out. Egyptian rousettes feed while holding the fruit close to the body, as a means of protecting the fruit from being pilfered by other bats. Stealing fruit is common, and these bats are aggressive when feeding (Kwiecinski and Griffiths, 1999).

• Primary Diet
• herbivore herbivore
  • frugivore frugivore

• Plant Foods
• fruit

Predation

Because of their frugivorous diet, Egyptian rousettes are sometimes considered a threat to fruit crops during the growing season. Plantation owners and farmers often hunt Egyptian rousettes or hire bounty hunters during the flowering and fruiting seasons to reduce the risk of crop damage and profit loss (Fujita and Tuttle, 1991). Egyptian rousettes, like many members of the Family Pteropodidae , are hunted for meat as well. As a result roost population densities have declined (Fujita and Tuttle, 1991). Natural predators have not been described but are likely to include aerial predators, such as falcons , and cave predators, such as snakes and mustelids . Their nocturnal habits, cave roosting, flight, and cryptic coloration all help them to avoid predation.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Egyptian rousettes are pollinators of many nocturnally flowering trees throughout paleotropical forests. Due to their frugivorous diets, they not only pollinate the flowers of fruit trees but also assist as the primary agent in seed dispersal for many tree species (Fujita and Tuttle, 1991). Egyptian rousettes are carriers for both ectoparasites and endoparasites throughout their geographic range. Ectoparasites that use Egyptian rousettes as hosts include: Spinturnix lateralis , Ancystropus leleupi , Ancystropus zelebori , Ancystropus lateralis , Ancystropus zeleborii , Liponyssus glutinosus , Liponyssus longimanus , Eucampsipoda africanum , Nycteribosca africana , Nycteribosca alluaudi , Eucampsipoda hyrtlii , Nycteribosca diversa , Thaumapsylla brevicep , Nycteribia pedicularia , Nycteribia schmidlii , Eucampsipoda africana , Afrocimex leleupi , Thaumapsylla breviceps , Archaeopsylla metallescens , and Alectorobius camicasi (Kwiecinski and Griffiths, 1999). Endoparasites that are found in Rousettus aegyptiacus include the hemosporidian Plasmodium roussetti and the roundworm Nycteridocoptes rousetti . Outbreaks of rabies are also found in populations of Egyptian fruit bats (Kwiecinski and Griffiths, 1999).

• Ecosystem Impact
• disperses seeds
• pollinates

Economic Importance for Humans: Positive

Throughout their range, Egyptian rousettes pollinate many commercially valuable fruit trees. This species also works to disperse seeds away from the parent plant, allowing seed germination and spread in unpredictable conditions (Fujita and Tuttle, 1991; Izhaki et al., 1995).

• Positive Impacts
• food food
• pollinates crops

Economic Importance for Humans: Negative

Rousettus aegyptiacus is perceived by many fruit farmers to be a pest of fruit crops grown commercially for human production throughout its range, though little evidence supports this and cases are often exaggerated (Albayrak et al., 2008).

Conservation Status

Rousettus aegyptiacus is considered a species of least concern by the IUCN. However, due to poaching and a negative interactions with commercial farming, there has been a decline in roosting sites (Albayrak et al., 2008).

Additional Links

Encyclopedia of Life

Contributors

Rachel Cohen (author), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Albayrak, I., N. Asan, T. Yorulmaz. 2008. The Natural History of the Egyptian Fruit Bat, Rousettus aegyptiacus, in Turkey (Mammalia: Chiroptera). Turkish Journal of Zoology , 32: 11-18.

Baydemir, N., I. Albayrak. 2006. A Study on the Breeding Biology of Some Bat Species in Turkey (Mammalia: Chiroptera). Turkish Journal of Zoology , 30: 103-110.

Bernard, R., G. Cumming. 1997. African Bats: Evolution of Reproductive Patterns and Delays. The Quarterly Review of Biology , 72: 253-274.

Fujita, M., M. Tuttle. 1991. Flying Foxes (Chiroptera: Pteropodidae): Threatened Animals of Key Ecological and Economic Importance. Conservation Biology , 5: 455-463.

Grzimek, B. 2003. Grzimek's Animal Life Encyclopedia . Farming Hills, Michigan: Gale Virtual Library.

Holland, R., D. Waters, J. Rayner. 2004. Echolocation Signal Structure in the Megachiropteran Bat Rousettus aegyptiacus Geoffrey 1810. The Journal of Experimental Biology , 207: 4361-4369.

Holland, R., D. Waters. 2007. The Effect of Familiarity on Echolocation in the Megachiropteran Bat Rousettus aegyptiacus. Behavior , 144: 1053-1064.

Izhaki, I., C. Korine, Z. Arad. 1995. The Effect of Bat (Rousettus aegyptiacus) Dispersal on Seed Germination in Eastern Mediterranean Habitats. Oecologia , 101: 335-342.

Korine, C., Z. Arad, A. Arieli. 1996. Nitrogen and Energy Balance of the Fruit Bat Rousettus aegyptlacus on Natural Fruit Diets. Physiological Zoology , 69: 618-634.

Korine, C., I. Izhaki, D. Makin. 1994. Population Structure and Emergence Order in the Fruit-bat (Rousettus aeyyptiacus: Mammalia, Chiroptera). The Zoological Society of London , 232: 163-174.

Kwiecinski, G., T. Griffiths. 1999. Rousettus egyptiacus. Mammalian Species , 611: 1-9.

Nogales, M., J. Rodriguez-Luengo, P. Marrero. 2006. Ecological Effects and Distribution of Invasive Non-Native Mammals on the Canary Islands. Mammal Review , 36: 49-65.

Nowak, R. 1999. Walker's mammals of the world . Baltimore: John Hpkins University Press.

Okia, N. 1987. Reproductive Cycles of East African Bats. Journal of Mammalogy , 68: 138-141.

Roberts, L. 1975. Confirmation of the Echolocation Pulse Production Mechanism of Rousettus. Journal of Mammalogy , 56: 218-220.

2006. "Egyptian Fruit Bat" (On-line). Rosamond Gifford Zoo. Accessed April 20, 2010 at http://www.rosamondgiffordzoo.org/assets/uploads/animals/pdf/EgyptianFruitBat.pdf .