Pteropus mariannus
Marianas flying fox

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)

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)

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.

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.

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)

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)

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)

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, Banack, and Cox, 2003)

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, Banack, and Cox, 2003)

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)

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.