Animal Diversity Web

Geographic Range

Pteropus tonganus is restricted to islands in the Pacific Ocean. It can be found distributed widely from islands near New Guinea through the Cook Islands. (Grant, et al., June 1997)

• Biogeographic Regions
• oceanic islands
  • native

• Other Geographic Terms
• island endemic

Habitat

Pteropus tonganus lives in a variety of habitats. These bats are typically found in lowland or montane native forests. Bare, upper branches of very tall trees in mature, primary forest are favored as a roosting habitat. However, roosts can located on cliff faces above the ocean or steep mountainsides. These bats are also known to use coastal swamps, mangrove swamps, inland swamp and marsh areas, as well as agricultural areas and human residential areas. (Brook, et al., June 2000; Miller and Wilson, 1997)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• forest
• rainforest
• scrub forest
• mountains

• Wetlands
• marsh
• swamp

• Other Habitat Features
• suburban
• agricultural

Physical Description

Pteropus tonganus is a black-backed bat with a contrasting orange or yellowish mantle, resembling many other sympatric species of bats. The total length of these bats averages 231 mm, and the mass averages 565 g. The forearm length, useful in helping distinguish P. tonganus from sympatric bat species, is between 120 and 160 mm, and the ears are always less than 31 mm in length. Some researchers think that males grow to be larger than females, but further information on this possible sexual dimorphism is not present in the literature. (Miller and Wilson, 1997)

Separation of P. tonganus from a similar species, P. samoensis, is made based on tooth patterns. Pteropus samoensis has a shorter, broader rostrum than does P. tonganus. Pteropus samoensis is also much larger than P. tonganus. It is easily distinguished from P. tonganus both by its larger size and by the absence of the white fur patch on the back of its neck which characterizes P. tonganus. The presence of a buffy mantle on the neck and upper back of P. tonganus is the only diagnostic characteristic that distinguishes it from P. samoensis in the field. (Banack, September 1998; Cox, 1983; Wilson and Engbring, 1992)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger

• Range mass

  191 to 1,099 g

  6.73 to oz

• Average mass

  565 g

  19.91 oz

• Range length

  151 to 262 mm

  5.94 to 10.31 in

• Average length

  231 mm

  9.09 in

Reproduction

The mating system of these animals is not documented.

Adult females generally have only one young per year, with a gestation of 140-192 days (4.6-6.3 months). The timing of the breeding season seems to vary some geographically, and there are reports that these animals may breed year round in American Samoa.

Mothers carry their young infants with them, tucked beneath a wing. Observed copulations often involve females who are nursing young, indicating that there may be a post-partum estrus cycle.

Young begin to fly when they are approximately three months old, and when they are only half to 3/4 of adult size. Weaned individuals are often seen flying and foraging with adults.

The young are usually not weaned until they are 4-6 months old, and can remain dependent on their mothers for a year. These animals do not reach sexual maturity until they are 1.5- 2.0 years old. (Cox, 1983; Falanruw, 1998; Miller and Wilson, 1997)

Although males and females associate with one another for most of the year, after mating and becoming pregnant, females are known to separate themselves from males to form "maternity camps." When the young are weaned, the females may rejoin the males. (Miller and Wilson, 1997)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• viviparous
• post-partum estrous

• Breeding interval

  These animals reproduce once per year.

• Breeding season

  Breeding season apparently varies geographically, with some populations breeding in June or July, and others possibly breeding year round.

• Range number of offspring

  1 to 2

• Range gestation period

  140 to 192 days

• Range weaning age

  4 to 6 months

• Range age at sexual or reproductive maturity (female)

  1.5 to 2 years

• Range age at sexual or reproductive maturity (male)

  1.5 to 2 years

The parental care of P. tonganus as not been well documented. However, it is known that females provide their offspring with milk. The female carries her offspring when it is very small. Weaned offspring often forage with adults, which might be their parents. It is not known what role males of this species play in parental care. (Cox, 1983; Miller and Wilson, 1997)

• Parental Investment
• altricial
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• post-independence association with parents

Lifespan/Longevity

Survival rates of Pteropus in the wild are unknown, but the maximum life span for a captive animal is 31 years. (Pierson and Rainey, 1992)

• Range lifespan
  Status: captivity

  31 (high) years

Behavior

Pteropus tonganus is primarily nocturnal. This species is gregarious, and may be found in large groups while foraging, and during daytime, when the bats gather at large colonial roosts, often with several hundred bats in a single tree. Colonies are extremely noisy and have a distinct odor that makes them easy to detect. (Brook, et al., June 2000; Cox, 1983; Craig, et al., October 1994)

When roosting, these bats hang upside-down from their feet, wrapping their wings around themselves as a shelter against inclemment weather. The feet are generally kept close together. When moving around in the roost, these bats are able crawlers, using their wings to drag themselves along. (Miller and Wilson, 1997)

Pteropus tonganus utilizes a broad array of plants for food. It takes pollen, nectar, and fruit from these trees. Foraging typically begins after dark, although some populations have been known to forage well before sunset. Such populations may be under hunting pressure, or food shortages may produce a need for daytime foraging. (Miller and Wilson, 1997)

While foraging, these bats may travel a long way from their roosting sites. They do not always eat their meals at the foraging site, though, and are known to carry large pieces of fruit away from their trees of origin. The bats manipulate the fruits with their hind legs, then smash the fruit against their palate to extract the juices and pulp, which are swallowed, and eject the seeds. (Miller and Wilson, 1997)

Pteropus tonganus are known to defend food resources. They may chase, bat at, and vocalize at intruding bats to warn them away. (Miller and Wilson, 1997)

The social structure of this species is not well understood. Males and females are sometimes found in the same colonies, but females separate from the males to form "maternity camps", only rejoining the males when the young are weaned. (Miller and Wilson, 1997)

• Key Behaviors
• arboreal
• flies
• nocturnal
• motile
• social
• colonial

Home Range

Home range size for this species has not been reported.

Communication and Perception

These bats are known to have high pitched vocalizations. Although not specifically mentioned in the literature, because of the way they roost so close to one another, these is undoubtedly some tactile communication between animals when roosting. The mother also has tactile communication with her offspring, whom she carries. There are reports of P. tonganus chasing one another in the context of defending a food resource, and batting at one another, indicating further visual and tactile communication. (Cox, 1983; Miller and Wilson, 1997)

• Communication Channels
• visual
• tactile
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

P. tonganus is a generalist among flying foxes, in that it consumes fruit, flowers, nectar, and pollen. Sometimes, these animals have been known to eat leaves.

Flying foxes swallow mostly the juices extracted after mastication of the fruit pulp and discard most of the fiber (in the form of an ejecta pellet). These ejecta pellets are made as a bat feeds on fruit pulp, compressing the fruit against the palate with the tongue. This action effectively squeezes out the juices, which are swallowed, and creates a pellet of dry fruit pulp. Some of this pulp is swallowed, but the animals spit most of it out.

Most fruit consumed by flying foxes have large seeds. These animals do not generally consume fruits until they are fully ripe, as that is when the fruits are most juicy, and easiest to smash up. They will consume unripe fruit in times of low availability of preferred fruit resources.

The plant species most commonly used for fruit in Samoa by P. samoensis and P. tonganus are Artocarpus altilus, Planchonella samoensis, and Syzygium inophylloides. P. tonganus is an extreme generalist and likely feeds upon more than 70 plant species. Because it has so many sources for food, this species is well prepared to period environmental disruptions, such as hurricanes.

After a major disturbance, such as a hurricane, these animals may eat leaves.

P. tonganus is extremely selective in choosing fruit within a tree. Animals will smell and occasionally bite many fruits before either eating. They may eat the fruit in the tree, or may remove one to eat in another location.

P. tonganus can be an agricultural pest, foraging on breadfruit, papayas, mangos, bananas and seasea fruits. Because they do not damage cash crops, however, they are thought mainly to be nuisances, and not damaging, by the Samoans. (Banack, September 1998; Cox, 1983; Miller and Wilson, 1997; Nelson, et al., October 2000)

• Primary Diet
• herbivore
  • folivore
  • frugivore
  • nectarivore

• Plant Foods
• leaves
• fruit
• nectar
• pollen
• flowers

Predation

Pteropus tonganus has few natural predators, partly because of its insular location. (Brautigam and Elmqvist, 1990)

Raptors and snakes are thought to be some of the major predators of flying foxes on islands. Peregrine falcons, Falco peregrinus, are known to subsist almost exclusively on flying foxes in New Caledonia , the Loyalty Islands, the Solomon Islands, and Vanuatu. Barn owls also have been reported to take P. tonganus. (Miller and Wilson, 1997)

• Known Predators

  • peregrine falcons (Falco peregrinus)
  • barn owls (Tyto alba)

Ecosystem Roles

Pteropus tonganus is an important as pollinator and seed disperser in Pacific island ecosystems. Without them, it would be difficult to maintain community diversity, because of the disturbances by storms. These animals are needed to affect the regeneration of dominant forest trees. They are also necessary to maintain genetic flow between islands. The loss of flying foxes may affect plants that have coevolved with them. About 30 per cent of plant species on Samoa are totally dependent on flying foxes for pollination or seed dispersal. This is remarkably high compared with forests in continental areas. Flying foxes like P. tonganus are keystone pollinators and seed dispersers, and disruptions of their populations would result in chain reaction of other extinctions--of plants and other animals that are dependent upon them. (Banack, September 1998; Brautigam and Elmqvist, 1990; Craig, et al., October 1994; Miller and Wilson, 1997)

• Ecosystem Impact
• disperses seeds
• pollinates
• keystone species

Economic Importance for Humans: Positive

These animals are hunted by local peoples for subsistence. Such hunting is sustained year-round. They are also commercially hunted and overharvested on many Pacific Islands to supply an exotic food market in Guam and for medicinal puposes. (Craig, et al., October 1994)

• Positive Impacts
• food
• source of medicine or drug
• pollinates crops

Economic Importance for Humans: Negative

Because of their feeding habits, these animals can potentially do damage to crops. (Miller and Wilson, 1997)

• Negative Impacts
• crop pest

Conservation Status

Because of commercial and subsistance hunting, this species is sometimes subject to overhunting. Because of their key role in local ecosystems, the potential damage to the area from decreases in population size are extreme.

Since 1989, P. tonganus has been listed in CITES Appendix I. The Appendix I listing provides for a prohibition on international trade in those species that are listed. However, the species is not listed as endangered, threatened, or otherwize at risk by the US Fish and Wildlife Service, or by the IUCN Redlist. (Brautigam and Elmqvist, 1990; Miller and Wilson, 1997)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  Appendix I

Other Comments

Pteropus tonganus plays an important role in the ethnobiology of the Samoan people. The legends of these people say that the Queen, Leutogi Tupa’itea, had displeased her husband, the king of Tonga. She was barren, so he chased her into the crotch of a Callophylum inophyllum tree. The villagers promptly set a huge fire beneath the tree. Just as the flames reached the Queen, a large flight of P. tonganus put out the flames. (Cox, 1983)

Contributors

Leslie Avalos (author), Humboldt State University, Brian Arbogast (editor), Humboldt State University.

Nancy Shefferly (editor), Animal Diversity Web.

References

Banack, S. September 1998. Diet selection and resource use by flying foxes (genus Pteropus). ECOLOGY, 79(6): 1949-1967.

Brautigam, A., T. Elmqvist. 1990. Conserving Pacific island flying foxes. ORYX, 24(2): 81-89.

Brook, A., C. Solek, A. Tualaulelei. June 2000. Roosting behavior of colonial and solitary flying foxes in American Samoa (Chiroptera: Pteropodidae). Pacific Science, 54(4): 301-311.

Cox, P. 1983. Observations on the natural history of Samoan bats. MAMMALIA, 47(4): 519-523.

Craig, P., T. Morell, P. Trail. October 1994. The decline of fruit bats in American Samoa due to hurricanes and overhunting. Biological Conservation, 69: 261-266.

Falanruw, M. 1998. On the status, reproductive biology and management of fruit bats of Yap. Micronesica, 21: 39-51.

Grant, G., P. Craig, P. Trail. June 1997. Cyclone-induced shift in foraging behavior in flying foxes in American Samoa. BIOTROPICA, 29(2): 224-228.

Miller, C., D. Wilson. 1997. Pteropus tonganus. Mammalian Species, 552: 1-6.

Nelson, S., M. Miller, E. Heske, G. Fahey. October 2000. Nutritional quality of leaves and unripe fruit consumed as famine foods by the flying foxes of Samoa. Pacific Science, 54(4): 301-311.

Pierson, E., W. Rainey. 1992. The biology of flying foxes of the genus Pteropus: A review. US Fish & Wildlife Resource Biologica Report, 90(23): 134-147.

Wilson, D., J. Engbring. 1992. The flying foxes Pteropus samoensis and Pteropus tonganus:status in Fiji and Samoa. US Fish and Wildlife Ser. Biol. Rep., 90(23): 36-38.