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Tadarida aegyptiacaEgyptian free-tailed bat

By Thomas Eiting

Geographic Range

Tadarida aegyptiaca, the Egyptian free-tailed bat, has an Old World distribution, stretching from Morocco across central and east Africa to southwest Asia, India, and Sri Lanka, excluding the Sahara desert. The range of T. aegyptiaca includes much of the African continent to South Africa. (Bernard and Tsita, 1995; Denys, et al., 1995; Nowak, 1994)

This species has a patchy distribution throughout its range. It is poorly known through northwestern Africa, but in other parts of its range it is quite abundant and widespread, including India and South Africa. (Advani, 1982; Bernard and Tsita, 1995; Denys, et al., 1995)

Habitat

Tadarida aegyptiaca is usually found in warm, semi-arid and arid regions. It is generally not found in forested or mountainous habitats. (Advani, 1982)

Egyptian free-tailed bats prefer rock crevices and cliff faces for diurnal roosts. They nest in human structures as well, including the roofs of houses and churches. They are also known to roost in caves, crevices, and dead trees. (Advani, 1982; Bernard and Tsita, 1995; Denys, et al., 1995)

  • Range elevation
    500 (high) m
    1640.42 (high) ft

Physical Description

Tadarida aegyptiaca is sexually dimorphic, with males slightly smaller than females. Males range in size from 11.0 to 20.0 g, with an average of 15.8 g, while females range from 13.8 to 20.5 g, averaging 16.3 g. The snout is long and slightly upturned at the lip. Ears are very large (18 to 23 mm long) and forward-pointing. The tragus is square with an accessory appendage. These bats have a grayish-brown dorsal coat, with particularly dark areas on the back of the head and the back. Tadarida aegyptiaca shares only with Tadarida brasiliensis among Tadarida the distinct separation of the ears along the top of the head. (Hoath, 2003; Nowak, 1994; Silva and Downing, 1995)

The wingspan of T. aegyptiaca averages 35.4 cm, while the wing area is 0.0130 m^2. The aspect ratio for the wings is 9.7, with a wing loading of 12.0 Nm^-2. Body length is 104 to 120 mm, tail length is 41 to 46 mm, and forearm lenth is 47 to 56 mm. The dental formula is 1/2, 1/1, 2/2, 3/3. (Denys, et al., 1995; Hoath, 2003; Norberg and Rayner, 1987)

  • Sexual Dimorphism
  • female larger
  • Range mass
    13.8 to 20.5 g
    0.49 to 0.72 oz
  • Average mass
    16.3 g
    0.57 oz
  • Range length
    104 to 120 mm
    4.09 to 4.72 in
  • Average wingspan
    35.4 cm
    13.94 in

Reproduction

There is no available data on the specific mating systems found in Tadarida aegyptiaca. As Advani (1982:19) states, “little is known about the ecology, biology, and ethology of this species.” (Advani, 1982)

Tadarida aegyptiaca is monoestrous and monotocous, and it breeds seasonally. Females are sexually mature during their first year, whereas males do not reach sexual maturity until their second year. In South Africa, spermatogenesis occurs in February. By July, over 90% of seminiferous tubules are in late spermatogenesis. Spermatozoa are released into the epididymes and stored in the caudal epididymis from July through September. The seminiferous tubules regress in August and September, becoming inactive from October to January. Late spermatogenesis produces associated increases in testis mass, diameter of seminiferous tubules, and height of seminiferous epithelium above the condition during spermatogenic inactivity. (Bernard and Tsita, 1995)

The uterus of Egyptian free-tailed bats is bicornuate in sexually mature females. The right uterine horn and ovary are significantly larger than their corresponding structures on the left side of the body. Follicular development occurs in April. Both ovaries develop up to the secondary follicle; later stages (including Graadian follicles and the corpus luteum) develop only in the right ovary. During the development of these follicles, the uterine endometrium becomes increasingly vascularized. (Bernard and Tsita, 1995)

Copulation, ovulation, and fertilization occur in August. Gestation lasts about four months; births occur in December. A second period of follicular development occurs between October and December but does not result in ovulation. Lactation continues through January; by February females are in anoestrus. (Bernard and Tsita, 1995)

A somewhat different reproductive cycle is observed for this species in the northern hemisphere. In India, mating occurs for three weeks from the end of May to early June. Ovulation immediately follows copulation. Gestation lasts from 77 to 90 days. Pregnancy occurs from June through September, with births occurring through October. (Kashyap, 1980)

  • Breeding interval
    Tadarida aegyptiaca breeds once yearly.
  • Breeding season
    Mating occurs between May and August, depending on latitude.
  • Average number of offspring
    1
  • Range gestation period
    77 to 120 days
  • Average weaning age
    1 months
  • Range time to independence
    8 (high) months
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Parental investment prior to parturition is high in both sexes. Males generate and store sperm for up to six months, whereas females exhibit a very long period of gestation (up to four months). Because females only give birth to one individual each year, they are able to devote all post-parturition resources to that pup. (Bernard and Tsita, 1995)

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

Lifespan/Longevity

Data for Tadarida aegyptiaca is lacking, but the lifespan for molossids in general averages about ten years, plus or minus about three years. (Barclay and Harder, 2003)

  • Average lifespan
    Status: wild
    10 years

Behavior

Like other molossids, Tadarida aegyptiaca has high-aspect-ratio wings and high wing loadings. These characteristics allow them to fly high and fast. Among Molossidae, however, T. aegyptiaca has one of the lowest wing loadings, so it likely flies slower than other species in this family. Coupled with its long, narrow-band echolocation calls, T. aegyptiaca is well suited to sustained, high-altitude flight. Physiologically, this species is able to sustain such prolonged, active flight because it has a relatively higher than expected oxygen carrying capacity in its blood for a mammal of its size. (Fenton and Griffin, 1997; Norberg and Rayner, 1987; van Aardt, et al., 2002)

Egyptian free-tailed bats ARE apparently active later in the night than many other sympatric species of bats. One study has shown that this species emerges fairly late in the evening (after 1840 h) and stays active well past midnight in the summer. (Fenton and Thomas, 1980)

  • Average territory size
    400 km^2

Home Range

No data exist documenting the home range of Tadarida aegyptiaca. The New World taxon Tadarida brasiliensis is known to have a home range of up to 400 km^2, with foraging flights extending to a distance of up to 25 km from their roosts. According to Nowak (1994), T. brasiliensis may in fact fly up to 65 km to foraging areas. (Nowak, 1994; Williams, et al., 1973)

Communication and Perception

Like all microchiropterans, Tadarida aegyptiaca depends on echolocation to some degree. Apart from navigation, T. aegyptiaca uses its echolocating abilities in active pursuit of insectivorous prey. (Fenton and Griffin, 1997)

There is some evidence to suggest that Egyptian free-tailed bats have a well-developed olfactory sense. The number of perforations in the cribriform plate for this species is much higher than other members of Vespertilionoidea. The cribriform plate facilitates the targeting of olfactory receptor (OR) axons with their specific glomeruli, leading to the first synapse of OR neurons with the olfactory bulb. Therefore, a higher number of cribriform plate perforations should be correlated with greater olfactory acuity. Rather than foraging, social behavior may be the reason for such olfactory prowess. However, in their study of scent-dispersing hairs (osmetrichia) in pteropodid and molossid bats, Hickey and Fenton (1987) found distinct hair types present in scent dispersing regions of several Tadarida, but not for the Egyptian free-tailed bat. (Bhatnagar and Kallen, 1974; Hickey and Fenton, 1987; Rowe, et al., 2005)

Food Habits

Egyptian free-tailed bats are echolocating aerial insectivores. Equipped with high-aspect-ratio wings, the actively hunts airborne prey, possibly up to 500 m above ground. They hunt using a long (10-20 ms), narrow bandwidth (5-10 kHz) search-phase echolocation call centered around 14-18 kHz. Echolocation frequencies can range up to 26 kHz, while the highest energy frequency is about 18 kHz. Tadarida aegyptiaca is considered a fast, long-range aerial-hawking insectivore. (Fenton and Griffin, 1997; Norberg and Rayner, 1987)

This species is known to consume insects of the orders Lepidoptera and Coleoptera. In a study of T. aegyptiaca in the Rajasthan desert of India (25-30ºN), Advani (1982) found a distinct seasonal variation in diet. During the winter (December through February at this latitude), the bats preferred Coleoptera, Orthoptera, Diptera, and Hymenoptera. Foods consumed in less quantities during the winter included Lepidoptera, Araneae, Neuroptera, and Dictyoptera. In the spring and summer, Coleoptera contributed to an even greater percentage of diet, nearly 40%. Orthoptera were also a major component of the diet, as was Lepidoptera. Isoptera and Hymenoptera made up a modest percent of the diet, while Dictyoptera, Diptera, and Odonata made only meager contributions. The monsoon season brought about drastic changes in dietary composition. Isoptera became the dominant food source, with Coleoptera, Hymenoptera, Lepidoptera, and Orthoptera contributing to most of the rest of the diet. Diptera and Neuroptera made minor contributions, and some plant material was found as well. In the post-monsoon period prior to winter (October and November), dietary preferences closely resembled those for the winter. Coleoptera and Hymenoptera predominated, while Orthoptera, Lepidoptera, Diptera, and Odonata all made significant contributions. Some Isoptera, Dictyoptera, Neuroptera, Araneae, and plant parts were also found. (Advani, 1982; Advani, 1982; Fenton and Thomas, 1980)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods

Predation

Tadarida aegyptiaca makes up a small part of the diet of owls. Young in roosts may fall prey to snakes. (Denys, et al., 1995)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Tadarida aegyptiaca is a common insectivore throughout much of its range. This species may also be a host to various viruses and other pathogens, including rabies. (Hill, and Smith, 1984)

Economic Importance for Humans: Positive

Egyptian free-tailed bats are geographically widespread consumer of potentially damaging pest animals such as Lepidoptera and Hymenoptera. They may thus serve to control populations of harmful insects in areas where they are abundant. (Advani, 1982; Hill, and Smith, 1984)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Because this species is known to roost in buildings, guano deposits may cause some risk of contamination by bacteria, arthropods, and other pests. However, guano deposits are usually small and dry, so this risk is slight. There is also some risk of rabies from coming into contact with this species, like all bats. Additionally, the coarse-scale distributions of disease outbreaks of all four strains of African filovirus (including Marburg and Ebola) overlap with the range of T. aegyptiaca. A total of 38 genera and well over 100 species of small mammal share this overlap, and no work yet has been performed on Egyptian free-tailed bats to show that they serve as a host for Filoviridae viruses. (Hill, and Smith, 1984; Peterson, et al., 2004)

Conservation Status

Tadarida aegyptiaca is not listed on any threatened or endangered species lists.

Other Comments

One subspecies, T. a. thomasi, occurs in abundance in the Great Indian Thar Desert. When referred to in the literature, this subspecies is also associated with the common name “wrinkle-lipped bat." In Egypt, the subspecies present is T. a. aegyptiaca. (Advani, 1982; Hoath, 2003)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Thomas Eiting (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

ultrasound

uses sound above the range of human hearing for either navigation or communication or both

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Advani, R. 1982. Feeding ecology of Tadarida aegyptiaca thomasi in the Indian desert. Zeitschrift für Säugetierkunde, 47: 18-22.

Barclay, R., R. Brigham. 1991. Prey detection, dietary niche breadth, and body size in bats: why are aerial insectivorous bats so small?. The American Naturalist, 137/5: 693-703.

Barclay, R., L. Harder. 2003. Life histories in bats: life in the slow lane. Pp. 209-253 in T Kunz, M Fenton, eds. Bat Ecology. Chicago: The University of Chicago Press.

Bernard, R., G. Cumming. 1997. African bats: evolution of reproductive patterns and delays. The Quarterly Review of Biology, 72/3: 253-274.

Bernard, R., J. Tsita. 1995. Seasonally monoestrous reproduction in the molossid bat, Tadarida aegyptiaca from low temperate latitudes (33°S) in South Africa. South African Journal of Zoology, 30/1: 18-22.

Bhatnagar, K., F. Kallen. 1974. Cribriform plate of ethmoid, olfactory bulb and olfactory acuity in forty species of bats. Journal of Morphology, 142: 71-90.

Bogdanowicz, W., M. Fenton, K. Daleszczyk. 1999. The relationships between echolocation calls, morphology and diet in insectivorous bats. Journal of Zoology, 247: 381-393.

Cumming, G., R. Bernard. 1997. Rainfall, food abundance and timing of parturition in African bats. Oecologia, 111: 309-317.

Denys, C., W. Bogdanowicz, S. Aulagnier. 1995. First record of Tadarida aegyptiaca (Chiroptera, Molossidae) from Morocco. Mammalia, 59/2: 266-268.

Fenton, M. 2003. Eavesdropping on the echolocation and social calls of bats. Mammal Review, 33/3: 193-204.

Fenton, M., D. Griffin. 1997. High-altitude pursuit of insects by echolocating bats. Journal of Mammalogy, 78/1: 247-250.

Fenton, M., D. Thomas. 1980. Dry-season overlap in activity patterns, habitat use, and prey selection by sympatric African insectivorous bats. Biotropica, 12/2: 81-90.

Hickey, M., M. Fenton. 1987. Scent-dispersing hairs (osmetrichia) in some Pteropodidae and Molossidae (Chiroptera). Journal of Mammalogy, 68/2: 381-384.

Hill,, J., J. Smith. 1984. Bats: A Natural History. London: British Museum of Natural History.

Hoath, R. 2003. A Field Guide to the Mammals of Egypt. New York: The American University in Cairo Press.

Hosken, D. 1997. Sperm competition in bats. Proceedings of the Royal Society of London B, 264: 385-392.

Kashyap, S. 1980. Reproductive cycle of the Indian molossid bat, Tadarida aegyptiaca . Current Science, 49/6: 252-253.

Norberg, U., J. Rayner. 1987. Ecological morphology and flight in bats (Mammalia; Chiroptera): wing adaptations, flight performance, foraging strategy and echolocation. Philospohical Transactions of the Royal Society of London B, 316: 335-427.

Nowak, R. 1994. Walker's bats of the world. Baltimore: The Johns Hopkins University Press.

Peterson, A., D. Carroll, J. Mills, K. Johnson. 2004. Potential mammalian filovirus reservoirs. Emerging Infectious Diseases, 10/12: 2073-2081.

Ratcliffe, J., M. Fenton, S. Shettleworth. 2006. Behavioural flexibility positively correlated with relative brain volume in predatory bats. Brain, Behavior and Evolution, 67: 165-176.

Rowe, T., T. Eiting, T. Macrini, R. Ketcham. 2005. Organization of the olfactory and respiratory skeleton in the nose of the gray short-tailed opossum Monodelphis domestica . Journal of Mammalian Evolution, 12: 303-336.

Silva, M., J. Downing. 1995. CRC Handbook of Mammalian Body Masses. Boca Raton: CRC Press.

Williams, T., L. Ireland, J. Williams. 1973. High altitude flights of the freetailed bat, Tadarida brasiliensis, observed with radar. Journal of Mammalogy, 54/4: 807-821.

van Aardt, W., G. Bronner, M. de Necker. 2002. Oxygen dissociation curves of whole blood from the Egyptian free-tailed bat, Tadarida aegyptiaca E. Geoffroy, using a thin-layer optical cell. African Zoology, 37/1: 109-113.

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