Pteropus mariannus

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.

• Biogeographic Regions
• oriental oriental
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

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 .

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

• Other Habitat Features
• riparian riparian

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger

Reproduction

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.

• Mating System
• polygynous polygynous

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.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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.

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

Lifespan/Longevity

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

Behavior

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.

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

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.

• Communication Channels
• tactile tactile
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• herbivore herbivore
  • frugivore frugivore

• Plant Foods
• leaves
• fruit
• nectar
• flowers

Predation

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.

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.

• Ecosystem Impact
• disperses seeds
• pollinates
• keystone species keystone species

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.

• Positive Impacts
• food 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.

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.

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.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

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

References

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 http://www.jstor.org/view/08888892/di995151/99p0196f/0 .

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 http://www.blackwell-synergy.com/links/doi/10.1046/j.1523-1739.2003.02049.x/full/ .

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 http://muse.jhu.edu/journals/pacific_science/v058/58.4wiles.pdf .

2006. "Mariana Fruit Bat" (On-line). Virginia Tech Fish and Wildlife Information Exchange. Accessed November 26, 2006 at http://fwie.fw.vt.edu/WWW/esis/lists/e051005.htm .

U.S. Fish and Wildlife Service. Mariana flying fox. 1018-AH55. Federal Register: Department of the Interior. 2005. Accessed November 02, 2006 at http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2005_register&docid=fr06ja05-14.pdf .