Pteropus mariannusMarianas flying fox

Geographic Range

Marianas flying foxes, Pteropus mariannus, are found on Pacific islands ranging from the Japanese Ryukyo Islands in the north, south to Guam. They are found on Guam, the Marianna Islands, Micronesian islands, Okinawa, and the Ryukyo Islands. ("Mariana flying fox", 2005)


Most of the islands on which Marianas flying foxes are found are tropical or subtropical. Large colonies can be found roosting in stands of native forest, smaller groups are found in isolated patches of native forest or in coconut tree groves (Cocos nucifera) groves. Forests these bats are found in usually have sparse undergrowth, a canopy that reaches 8 to 15 meters and scattered with taller trees that tower above the dominant canopy. Preferred roosting trees are C. nucifera, Ficus prolixa, Ficus species, Hibiscus tiliaceus, and Pandanus tectorius. ("Mariana flying fox", 2005; "Mariana Fruit Bat", 2006; Wiles, 2004)

Physical Description

Marianas flying foxes are medium-sized bats, weighing 330 to 577 grams. Their forearms measure 34 to 54mm. Wingspans range from 860 to 1065 mm. Overall length, from snout to rump, is 195 to 240mm. Males are usually a little larger than females. Mariana flying foxes are handsome bats, with black to brown fur over most of their body, flecked with silver hairs. The shoulders (mantle) and the sides of the neck are bright yellow to golden-brown. Their distinctly fox-like head, which gives these bats their name, is brown to dark brown. They have well-formed, rounded ears and large eyes. ("Mariana flying fox", 2005; "Mariana Fruit Bat", 2006)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • Range mass
    330 to 577 g
    11.63 to 20.33 oz
  • Range length
    195 to 240 mm
    7.68 to 9.45 in
  • Range wingspan
    860 to 1065 mm
    33.86 to 41.93 in


Marianas flying foxes are polygynous. Males form harem groups within breeding colonies. Non-breeding males will form bachelor groups or live on their own. (Wiles, 2004). In harems, males are usually accompanied by 2 to 15 females. In Guam, the average sex ratio was observed to be 38 to 72 males per 100 females. Mating mostly occurs during the day in the harems but will occasionally occur at night. ("Mariana Fruit Bat", 2006; Wiles, 2004)

Reproduction occurs year-round. In Guam, mating and nursing have been observed throughout the year, indicating no apparent peak in births. Females give birth to one offspring per year. Gestation length is 4.5 and 6 months. Age at weaning and first flight is unknown. Sexual maturity occurs between 6 and 18 months of age. Other Pteropus species become sexually mature at 18 months. ("Mariana flying fox", 2005; Wiles, 2004)

  • Breeding interval
    Females give birth to one offspring each year.
  • Breeding season
    Breeding occurs throughout the year.
  • Range number of offspring
    1 to 1
  • Range gestation period
    4.5 to 6 months
  • Range age at sexual or reproductive maturity (female)
    6 to 18 months
  • Range age at sexual or reproductive maturity (male)
    6 to 18 months

Young bats are carried by their mothers until they are too large to carry any longer. They are then left at the roost while the mother forages. While roosting, females fold their pup into their wings, and the large lump that creates in the mother's silhouette can be seen from a distance. (Wiles, 2004)

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


Nothing could be found on the lifespan of this species. In captivity, Pteropus species have been know to live about 30 years.


These bats are sedentary and live in colonies. Males form harems or bachelor groups. Some males will also lead solitary lives at the edge of the colony. Although they are sedentary, these bats are strong flyers and are capable of traveling long distances. They have been observed flying between islands in the Marianna Islands, with distances of 3 to 62 miles between islands. These distances are traveled mainly for feeding purposes. On an island, these bats travel 10 to 12 km to reach feeding grounds. During the day, Marianas flying foxes mostly sleep but will take part in grooming, breeding, scent rubbing, and marking territories. Males defend their roosting territories to maintain breeding rights over females in their harem. Females do not appear to be bound to any particular harem. ("Mariana flying fox", 2005; "Mariana Fruit Bat", 2006)

Home Range

Marianas flying fox home ranges have not been reported.

Communication and Perception

Chemical scent marking plays a role in establishing territories and grooming plays a role in establishing and maintaining social bonds. Other species of flying foxes take part in aerial displays, vocalization that varies with the situation, and scent marking. Pteropus species do not echolocate, instead they use their excellent vision in low light and their sense of smell to find food and navigate.

Food Habits

Marianas flying foxes are frugivorous, but also eat flowers and leaves on occasion. They forage in agroforest, pandanus savanna, swamp forests, and sometimes visit coconut groves. Their favorite fruits are breadfruit (Artocarpus mariannensis, A. altilis), papaya (Carica papaya), Cycas circinalis, figs (Ficus spp.), Pandanus tectorius, Terminalia cattappa, flowers from Ceiba pentandra, and coconut (Cocos nucifera). These bats have been observed traveling 10 to 12 km to reach feeding grounds. ("Mariana flying fox", 2005)

  • Plant Foods
  • leaves
  • fruit
  • nectar
  • flowers


Marianas flying foxes have few natural predators. There are only two that are known, brown tree snakes (Boiga irregularis) and humans. Humans will use these bats for their meat or kill them for consuming fruit crops. It's also possible that large owls will take these flying foxes while they are foraging at night. (Cox, et al., 1991)

Ecosystem Roles

Flying foxes in general are keystone pollinators and seed dispersers in the southwestern Pacific. They are the only native frugivorous mammals in that region and are very important in forest regeneration through seed dispersal. (Cox, et al., 1991)

Economic Importance for Humans: Positive

These bats are an important cultural food for the native people of the Marianna Islands, and they will often risk fine and imprisonment to have Marianna flying foxes. Their role as pollinators and seed dispersers is also a positive impact on the native ecosystems of the southwestern Pacific islands. (Monson, et al., 2003)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Marianna flying foxes often eat the fruits of cycads, which makes their meat toxic and can lead to a neuropathological disease called amyotrophic lateral sclerosis-Parinsonism dementia complex, eventually leading to death. These bats also bioaccumulate DDT and other toxins. ("Mariana flying fox", 2005; Monson, et al., 2003)

Conservation Status

Marianna flying foxes are currently listed as threatened by the U.S. Fish and Wildlife Service and endangered by the IUCN. They are also on CITES Appendix I. The cause of their decline is habitat loss by timber removal, natural disasters, and through the destructive habits of non-native, invasive ungulates. Populations are also in decline as a result of hunting for food and killing as a crop pest. ("Mariana flying fox", 2005; Cox, et al., 1991)

Other Comments

The common name for this bat is Marianna flying foxes (Pteryopus mariannus Desmarest, 1822). Synonyms are Pteropus keraudren, Quoy and Gaimard, 1824, Pteropus paganesis, Yamashima, 1932, and Pteropus ulthiensis, Yamashima, 1932.


Tanya Dewey (editor), Animal Diversity Web.

Brianne Winter (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.



uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

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.


uses smells or other chemicals to communicate


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.


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.


A substance that provides both nutrients and energy to a living thing.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


an animal that mainly eats fruit


An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.


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).

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).


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.


active during the night


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

World Map


having more than one female as a mate at one time


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).


remains in the same area


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


associates with others of its species; forms social groups.


uses touch to communicate


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


The term is used in the 1994 IUCN Red List of Threatened Animals to refer collectively to species categorized as Endangered (E), Vulnerable (V), Rare (R), Indeterminate (I), or Insufficiently Known (K) and in the 1996 IUCN Red List of Threatened Animals to refer collectively to species categorized as Critically Endangered (CR), Endangered (EN), or Vulnerable (VU).


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


uses sight to communicate


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

year-round breeding

breeding takes place throughout the year


2006. "Mariana Fruit Bat" (On-line). Virginia Tech Fish and Wildlife Information Exchange. Accessed November 26, 2006 at

U.S. Fish and Wildlife Service. Mariana flying fox. 1018-AH55. Federal Register: Department of the Interior. 2005. Accessed November 02, 2006 at

Cox, P., T. Elmqvist, E. Pierson, W. Rainey. 1991. Flying Foxes as Strong Interactors in South Pacific Island Ecosystems: A Conservation Hypothesis. Conservation Biology, 5/4: 448-454. Accessed November 30, 2006 at

Monson, C., S. Banack, P. Cox. 2003. Conservation Implications of Chamorro Consumption of Flying Foxes as a Possible Cause of Amyotrophic Lateral Sclerosis-Parkinsonism Dementia Complex in Guam. Conservation Biology, 17/3: 678. Accessed November 30, 2006 at

Wiles, G. 2004. Population Size and Natural History of Mariana Fruit Bats (Chiroptera: Pteropodidae) on Sarigan, Mariana Islands.. Pacific Science, 58/4: 585-596. Accessed November 30, 2006 at