Old World Fruit Bats II (All Other Genera)

(All other genera)

Class: Mammalia

Order: Chiroptera

Suborder: Megachiroptera

Family: Pteropodidae

Thumbnail description
Small to the largest bats, dog-like or lemur-like faces, relatively small external ear with no tragus, no echolocation with one exception, visually oriented with color vision, claws on first and second digits, tail is short, vestigial or absent; includes fruit bats, flying foxes, blossom bats, rousette bats, and tube-nosed bats

Size
Head and body length, 2–15.7 in (5–40 cm); weight, 0.4–42.3 oz (12–1,200 g)

Number of genera, species
38–41 genera, approximately 106 species (excluding Pteropus)

Habitat
Forest, woodland, montane forests, savanna, scrub, swampy forests, and mangrove

Conservation status
Extinct: 3 species; Critically Endangered: 6 species; Endangered: 3 species; Vulnerable: 20 species; Lower Risk/Near Threatened: 15 species; Data Deficient: 3 species

Distribution
Tropical and subtropical regions of the Old World (i.e., the Paleotropics) ranging from Africa east to Australia and the Caroline and Cook Islands

Evolution and systematics

The evolution of bats is not well known. Because bat bones are fragile, their fossil record is very incomplete. The oldest fossil bats date back to 50 million years ago (mya) and were found at sites in Wyoming and Germany. These specimens are fully evolved bats. The oldest megachiropteran fossils date to around 35–25 mya in the Oligocene of Italy.

In the late 1980s Jack Pettigrew of the University of Queensland presented evidence that the megachiropterans were a convergence with the Microchiroptera (insectivorous bats). He pointed out that fruit bats and primates shared derived traits, in particular the neural pathway from the retina of the eye to the tectal (roof of the midbrain) portion of the brain. He concluded that the order Chiroptera was polyphyletic and that the megachiropterans were actually flying primates. This proposal stimulated discussion for several years. By 1994 Simmons presented molecular evidence from over 30 studies that supported the chiropteran monophyly. The two suborders, Microchiroptera and Megachiroptera, are much more closely related to each other than to primates. Nevertheless, the primates are close relatives, along with the colugos and tree shrews. These four mammal groups are often grouped together in the grandorder Archonta. It is interesting to note that Linnaeus, the founder of taxonomy, included all four of the archontan taxa in the order Primates.

Physical characteristics

Body size of fruit bats, flying foxes, rousettes, tube-nosed bats, and blossom bats ranges from small (around 0.4 oz/12 g) to large (42.3 oz/1,200 g). They have dog-like faces with long snouts, which is the reason that some species are called flying foxes. Fruit bats differ in a number of features from the small insectivorous bats of the order Microchiroptera. Fruit bats are primarily visually oriented and have large forward facing eyes that give them depth perception. The retina contains cones for color vision. These bats have good daytime and nocturnal vision, but they are inactive in complete darkness. Except for the rousette bat, fruit bats do not echolocate. Consequently, most have a simple and relatively small external ear without a tragus. The sense of smell is also well developed in fruit bats. All fruit bats have claws on the first digit (thumb) and, unlike microchiropterans, most have claws on the second digits of the wing skeleton. Wings tend to be broad. These bats do not fly as fast as microchiropterans nor do they perform the aerobatics of their relatives. They do travel long distances and have good hovering ability; some are even able to fly backwards. The wing is mostly devoid of fur. The wing membrane of one genus extends to the vertebral column creating a naked back. The tail is short, vestigial, or absent altogether. The uropatagium, a segment of membrane between the legs that helps provide lift, is not present in those species with a reduced or absent tail. The legs are splayed to the side like a reptile rather than underneath the body like other mammals. The hind paws are completely clawed. They are used predominantly for hanging upside down and, in conjunction with the clawed thumb, are used for climbing in trees.

The number of teeth is variable and ranges from Rousettus with a dental formula of (I2/2 C1/1 P3/3 M2/3) × 2 = 34 teeth, to Nyctimene and Paranyctimene having a dental formula of (I1/0 C1/1 P3/3 M1/2) × 2 = 24 teeth. The teeth of other species are intermediate in number: 32, 30, or 28 teeth in total. The incisors are small, canines are always present, and the cheek teeth (premolars and molars) tend to be flat and wide, suitable for crushing soft fruit. Tongues are sometimes long and mobile, especially in the nectarivorous species. In fruit eating species the tongue is used to crush food against the transverse ridges of the palate (roof of the mouth). In some species, such as the hammer-headed fruit bat, these ridges are highly developed.

The most common pelage (fur coat) color is dark brown, but this is highly variable. The ventrum (the belly side) is often a lighter color, such as off white or yellow.

Sexual dimorphism is often present. The most common difference between males and females is body size, but males may also differ in pelage patterns, especially on the head. Other male characteristics are hair tufts on the shoulders (epaulettes) and large pharyngeal sacs in the thoracic region.

Distribution

The fruit bats are confined to the Old World, ranging from Africa to Southeast Asia to Australasia and the islands of the western Pacific.

Habitat

Most fruit bats live in humid forests of the tropical and subtropical regions of the Old World (Paleotropics).

Behavior

For the most part fruit bats are gregarious animals that form roosting colonies (often called camps) during the day of from 10 to over one million animals. Most roost in trees, but some occupy caves or human-built structures. Many species have grooming sessions just before they take flight. Some of the smaller species and a few of the nectarivorous species roost alone. In many cases when fruit bats take flight from the roost they forage alone.

Fruit bats are crepuscular, meaning they are most active at dawn and dusk. They are occasionally active during the day when moving from one location to another in a tree for thermoregulation.

Feeding ecology and diet

Fruit bats, as the name implies, are mainly frugivorous. However, some genera consume mainly nectar and pollen. Unlike the microchiropterans, there are no insectivorous fruit bats. Fruit bats obtain a piece of fruit and fly to a feeding tree.

There they hang upside down by one foot, press the fruit to their chest with the other foot, and bite off pieces. They ingest the fruit, crush it against the palate with the tongue, consume the juice, and spit out the pulp and seeds. Because of this feeding behavior they are important seed dispersers. Nectarivorous bats, such as the blossom bats, have a long narrow snout and a long protrusible tongue that enables them to reach nectar in flowers. Some are pollinators and have a brushlike tip on the tongue for collecting pollen. During feeding some of the pollen sticks to their noses and the fur on the snout. When they visit the next flower they leave some pollen from the first flower.

Reproductive biology

Most fruit bats have two breeding seasons a year, although the females of most species only conceive in one of the seasons. They tend to be polygamous with males attempting to mate with as many females as possible (although many do not mate at all) and females mating with two or more males. There is at least one species that is believed to be monogamous. Delayed implantation occurs in some species. The ovum is fertilized, but the zygote goes into stasis rather than implanting in the uterine wall. When conditions are right the zygote is implanted and begins development. Births are usually synchronized to correspond with the period of greatest food availability. Single births are the norm. Gestation is between four and six months.

Conservation status

Old World fruit bats are threatened as a group. Three recent species have already become Extinct. Six are Critically Endangered, and three are Endangered. Twenty species are Vulnerable. Fifteen species have Near Threatened status. Thus, of the approximately 102 species of megachiropterans outside of the genus Pteropus, 46% are on the World Conservation Union (IUCN) Red List of species of concern. The main threats to Old World fruit bats include habitat destruction, hunting and sale of bush meat, and extermination because they are perceived as agricultural pests.

Significance to humans

Old World fruit bats are often the major pollinators of a particular region. Removal of these bats can actually harm agriculture. At the same time fruit bats are viewed as pests that destroy crops. In at least one case this has been demonstrated not to be true; the bats were being blamed for damage caused mainly by monkeys. More study needs to be done on this issue. Old World fruit bats are exploited commercially as meat in some parts of their range.

Species accounts

Resources

Bates, P. J. J., and D. L. Harrison. Bats of the Indian Subcontinent. Sevenoaks, UK: Harrison Zoological Museum Publication, 1997.

Corbet, G. B., and J. E. Hill. A World List of Mammalian Species. 3rd ed. New York: Oxford University Press, 1991.

Eisentraut, M. "The Old World Fruit Bats." In Grzimek's Animal Life Encyclopedia, Vol. 11, edited by B. Grzimek. New York: Van Nostrand Reinhold Company, 1972.

Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File Publications, 1984.

Mickleburgh, S. P., A. M. Hutson, and P. A. Racey. Old World Fruit Bats: An Action Plan for their Conservation. Gland, Switzerland: International Union for the Conservation of Nature, 1992.

Nowak, R. M. Walker's Mammals of the World. 6th ed. Baltimore: Johns Hopkins University Press, 1999.

Qumsiyeh, M. B. The Bats of Egypt. Lubbock, TX: Texas University Press, 1985.

Acharya, L. "Epomophorus wahlbergi." Mammalian Species 394 (1992): 1–4.

Balasingh, J., S. Suthakar-Isaac, and R. Subbaraj. "Tent Roosting by the Frugivorous Bat Cynopterus sphinx in Southern India." Current Science 65 (1993): 418.

Bradbury, J. W. "Lek Mating Behavior in the Hammer-headed Bat." Zeitschrift fur Tierpsychologie 45 (1977): 225–255.

Owen-Ashley, N. T., and D. E. Wilson. "Micropteropus pusillus." Mammalian Species 577 (1998): 1–5.

Simmons, N. B. "The Case for Chiropteran Monophyly." American Museum Novitiates 3103 (1994): 1–54.

Tuttle, M. D. "Fruit Bats Exonerated." Bats 1 (1984): 1–2.

International Union for the Conservation of Nature. "Red List of Threatened Species." 2000 [June 11, 2003].

[Article by: Marcus Young Owl, PhD]