The Egyptian fruit bat, or Egyptian rousette ( Rousettus aegyptiacus ), is a megabat species found across Africa, the Middle East, the Mediterranean, and the Indian subcontinent. It holds the distinction of being the only frugivorous bat species in Europe. It is one of three Rousettus species with an African-Malagasy range, though the only species of its genus found on continental Africa. The common ancestor of the three species colonized the region in the late Pliocene or early Pleistocene. Because of its consumption of commercially-grown fruits, the Egyptian fruit bat is considered a pest by farmers.
Taxonomy and Description
The Egyptian fruit bat was first described in 1810 by French naturalist Étienne Geoffroy Saint-Hilaire as Pteropus egyptiacus. The species is traditionally divided into six subspecies. It is considered a medium-sized megabat, with adults weighing 80-170 g (2.8-6.0 oz) and possessing wingspans of approximately 60 cm (24 in).
Egyptian fruit bats have light-brown or medium-gray bodies, dark brown wings with a claw at the end, a long muzzle, and a two-foot wingspan. They weigh up to 6 ounces and measure between 5-7.5 inches long on average. The fur on its body is relatively short and consists of soft and sleek strands. On its back, the fur’s coloration ranges from dark brown to gray-brown, while the coloration on its underside is pale brown with a yellowish-brown collar around its neck. Its wings are of a darker brown than its body and the wing membranes attach to the leg at the first toe. Males and females have similar coloration.
The Egyptian fruit bat has one of the greatest ratios of brain weight to body weight of any bat species. It is well adapted to seeing in low light and possesses a highly developed sense of smell. The regions of the brain associated with sight and smell are similarly well-developed. Its eyes are large and well-developed, while its ears are considered medium-length.
Distribution and Habitat
The Egyptian fruit bat is extensively dispersed across various locations and occurs throughout Africa, the Middle East, Pakistan and northern regions of the Indian subcontinent. In the Mediterranean region, it occurs on the mainland coast of Turkey and the island of Cyprus.
Read also: Social Status and Diet in Ancient Egypt
These bats inhabit a range of habitats, from tropical to arid areas, relying on a sufficient supply of fruit trees and suitable sites for roosting. They can be found in forests, savanna, and Turkey’s Mediterranean scrub forests. Their geographic range extends from 15 degrees north through 37 degrees south, and up to 40 degrees north in southern Turkey, and the Arabian Peninsula.
Social Behavior and Roosting Habits
The Egyptian fruit bat is a highly social species, usually living in colonies. Their groups vary in size; small colonies may have just 20 individuals, but large ones may include more than 9,000. Egyptian fruit bats live in groups that range from 20 to 40 individuals to huge colonies of 9,000. The colonies prefer roosting during the day in dark environments that are slightly humid, such as ruins and caves, though small colonies are seen roosting in trees. These bats roost close together to reduce the effect of temperature fluctuations. This close contact enables communication with one another throughout the day when roosting. Throughout the day during roosting, they have frequent grooming.
Diet and Foraging Behavior
The Egyptian fruit bat is frugivorous, consuming mostly fruit and leaves. It leaves its roost at dusk to begin foraging.
The Egyptian fruit bat has a flexible diet, consuming any soft, pulpy fruit from fruiting trees, comprising Persian lilacs, loquat, figs, and wild dates. The type of fruit consumed is influenced by overall availability depending on the season and habitat type. Egyptian fruit bats eat holding their food close to their body, guarding it from other bats. While eating, it will hold the fruit tightly against its body to prevent theft by other bats. These bats hold fruit close to their body while they feed to prevent other bats from stealing their food.
The Egyptian fruit bat usually makes multiple, short flights from its roost to various fruiting trees. It prefers to pick fruit and carry it back to the roost or another tree before eating it. A study of Egyptian fruit bats in Cyprus noted that if Egyptian fruit bats are aware of an abundant fruit source somewhere, they will travel distances of about 15-20 km (9.3-12.4 mi) to reach it. It eats large quantities of fruit each evening, equivalent to about 50 to 150 percent of its weight. Pulp and juice is consumed; after thorough chewing, the seeds are spit out. Its intestinal transit time is rapid, with food passing through the small and large intestines in 18-100 minutes.
Read also: Feeding Egyptian Tortoises
Reproduction and Development
Egyptian fruit bats may exhibit both polygynandrous (promiscuous - both males and females breed with multiple mates) or polygynous (one male mates with multiple females) mating systems. The Egyptian fruit bat is a polygamous species, with biannual breeding seasons. Breeding typically occurs between April and August and again from October to February. When the breeding season begins, the bats within the colony separate based on sex. The males gather together to form bachelor groups while the females form maternity colonies.
Female bats have control over copulation; therefore, to increase the chances of mating, male Egyptian fruit bats will provide a nuptial gift to the female bat. The nuptial gifts are fruits that the male allows the female to scrounge. By allowing the female to scrounge, it strengthens the bond between the pair, thus increasing the probability of the female copulating with a given male.
Females typically give birth to only a single offspring each year (called a "pup"), but twins are occasionally born, after a gestation period of around 115 to 120 days. A single pup is raised, though sometimes twins are born. Colonies will synchronize births, so all pups are born at the same time. Gestation is about four months most pups can fly by the time they are three months old. Newborn Egyptian fruit bat pups are altricial at birth with their eyes shut until they are nine days old. The female carries the pup until it is six weeks old, which is when it can hang in the roost on its own. Afterwards, the pup is left in the roost while the mother forages. Before the pup is left in the roost, the mother repeatedly transports the pup to the same tree and is left there for the night while the mother forages. The pup learns this location and visits it first when at about three months of age, the pup will leave the roost on its own to forage for its food. They only become independent from their mothers after nine months, once they have finally reached their adult physique. Young reach their full adult size and weight around the age of 9 months, and at about this time they become independent of their mothers.
Ecological Role
The Egyptian fruit bat serves as a seed disperser of large and small seeds. Seeds are dispersed 25-400 m (82-1,312 ft) away from parent trees. Egyptian fruit bats are ecologically important as pollinators or seed dispersers for many species of trees and plants. Egyptian fruit bats pollinate many trees that flower nocturnally throughout paleotropical forests.
Echolocation and Communication
The Egyptian fruit bat is among the few megabats using echolocation. Although it is considered a primitive form compared to non-megabat species, this has been questioned. A few other megabat species echolocate via creating clicks with their wings. It echolocates by emitting a series of sharp, bidirectional click pairs with its tongue and by altering teeth and lip positions. The clicks are normally slow and constant, but speed up dramatically when the bat approaches an object. Egyptian fruit bats have eyes adapted for night vision, but they also use echolocation. They are one of the three members of their genus that use both strategies to find food.
Read also: Explore the pros and cons of fruit juice detoxes.
It also makes use of a range of vocalizations for communication, including grunts and screeches, to communicate with other bats within the colony. As a result, a large roosting colony can be a deafening cacophony. Additionally, according to several studies, it is thought that because of their constant exposure to thousands of other individuals, they can form their own language to interact with one another about specific topics such as food.