Pteropus pselaphon 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Chiroptera Pteropodidae

Scientific Name: Pteropus pselaphon Lay, 1829
Common Name(s):
English Bonin Flying Fox, Bonin Fruit Bat
French Renard volant des Îles Bonin , Roussette des Îles Bonin
Spanish Zorro Volador De Las Isla Bonin

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(ii,iii,iv); D ver 3.1
Year Published: 2017
Date Assessed: 2017-02-13
Assessor(s): Vincenot, C.
Reviewer(s): Mildenstein, T.
Contributor(s): Ishii, N. & Maeda, K.
This species is listed as Endangered because it is known from 3-5 locations on the islands of Chichi, Haha, Kita-Iwo, Iwo, and Minami-Iwo in the Ogasawara/Bonin archipelago and its area of occupancy (AOO) is limited (ca 60 km²). Under anthropogenic pressure (i.e., reduction in extent and quality of habitat and direct conflicts with agriculture), the size of the subpopulation on Haha island is assumed to have strongly declined and may disappear in the near future, thereby further reducing the number of locations. The local population on Iwo island, which is military territory, is also very fragile due to limited size and habitat availability. Additionally, the population size of P. pselaphon is thought to number in total 300 to 400 individuals at most. A precautionary estimate of the number of mature individuals thus falls below the threshold of 250 individuals.

Concurrently with the inscription of Ogasawara islands on UNESCO’s World Heritage List, a conservation plan for P. pselaphon has been devised. The situation of this species is nonetheless still very fragile and its recovery strongly depends on the effective implementation of planned conservation measures, on the continuation of current conservation efforts on Chichi-jima, and on their extension to the other islands. Under the pressure of local communities of farmers, early signs of disengagement have transpired and should be followed carefully. If conservation actions were practically hindered or diminished, a reassessment should be undertaken promptly. The latter could rely on criteria A3cd or C1 for a Critically Endangered assessment, which would be readily met for subpopulations projected to face such circumstances.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is known only from the Bonin Islands in Japan, which are located on the Izu-Bonin-Mariana arc, about 1,000 km south of Tokyo and halfway to the Mariana Islands. It has been observed in the Ogasawara archipelago (Chichi-jima and Haha-jima) and in the Volcano archipelago (Kita-Iwo-jima, Iwo-jima, and Minami-Iwo-jima) (Abe et al. 2005). It was also once observed flying on Muko-jima (Harata 2010) and traces of foraging were found on other islands of the chain (Nishi-jima, Ani-jima, Ototo-jima, and Higashi-jima), but no local population has been reported at these locations.
Countries occurrence:
Japan (Kazan-retto, Ogasawara-shoto)
Additional data:
Estimated area of occupancy (AOO) - km2:60Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:10703
Number of Locations:3-5Continuing decline in number of locations:Yes
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The species was considered locally extinct on Chichi-jima in the 1970s, but it was rediscovered in 1986. The local population, which is assumed to be the largest of all and has experienced a strong decline, now numbers 100-150 individuals and has been slowly growing in recent years. On the other hand, the situation on Haha-jima—the second largest island—has not been precisely assessed. Several hundred individuals lived on the island in the 1970s (Ministry of Environment 2010), but a report from 1999 indicated that only three individuals could be found (Ministry of Environment 2012). A local extinction is thus imminent. Population estimates for Kita-iwo-jima, Minami-iwo-jima, and Iwo-jima are not available. Kita-iwo-jima and was assumed to host 25 to 50 individuals based on a short survey done in 2001, whereas brief observations on Minami-iwo-jima in 1982 and 2006 suggested that around 100 flying foxes might live on this island. These two islands are uninhabited. Only very few P. pselaphon individuals allegedly inhabit Iwo-jima, the access to which is restricted to military personnel only.
Current Population Trend:Stable
Additional data:
Number of mature individuals:200-250
Population severely fragmented:Yes
No. of subpopulations:5

Habitat and Ecology [top]

Habitat and Ecology:Pteropus pselaphon is found mainly in forests. This species is mostly nocturnal, yet diurnal activity has been reported on uninhabited islands. It forms colonies of up to several dozens of individuals that return to the colonial roost to sleep during the day. When resting, individuals often gather on branches and form ball-shaped clusters of ~6-20 individuals. These clusters improve thermoregulation and incidentally impact the mating system, which has been described as female-defence polygyny (Sugita and Ueda 2013).

Pteropus pselaphon is a dietary generalist (or more precisely a sequential specialist), switching food source at the individual level depending on availability. Fruits of the endemic Takonoki tree (Pandanus boninensis) are particularly favoured by this flying fox, which also regularly feeds on a variety of leaves and nectar. It is also known to feed on fallen fruits on the ground and to drink from streams. On inhabited islands, orchards are also targeted, resulting in this species being seen as a pest by some farmers (Vincenot, unpub. data). The limited extent of damages, however, does not support this characterization.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):6-8

Use and Trade [top]

Use and Trade: Hunting of this species for use and export occurred in the past (20th century) but has now stopped.

Threats [top]

Major Threat(s): On Chichi-jima and Haha-jima, disturbance at roost sites and deforestation have reportedly impacted this species, although the extent of the latter has possibly reduced with the islands’ listing as UNESCO Natural World Heritage. Of greater concern are accidental mortality in nets placed around fruiting trees in orchards and potential isolated retaliations by farmers facing crop damages. Important efforts have been made by authorities to equip farmers with nets, but the situation is not yet entirely satisfactory with respect to equipment and coverage.

Feral cats and dogs also represent known predators, while competition with rats may also be an issue. The lack of fear exhibited by this flying fox towards humans as well as its peculiar habit to sometimes feed and drink on the ground may be aggravating factors.

Strong typhoons occasionally sweep the region and, based on observations on flying foxes elsewhere, may be detrimental to the viability of such small populations. The impact of military activities by the Japanese army on Iwo-jima is left to be determined.

This bat was hunted and exported to an unknown extent during the 20th century, but this practice has ceased.

Conservation Actions [top]

Conservation Actions: This species was designated as a Natural Monument in 1969 under the Law for the Protection of Cultural Properties and as National Endangered Species” in 2009, whereby capture and disturbance without permission are prohibited. A National Wildlife Protection Area that includes the species' habitat was established in 1980. This species is categorized as Endangered (EN) on the Tokyo Red List (Tokyo Metropolitan Government 2014) as well as on the national Japanese Red List (Ministry of Environment 2012). A conservation plan has been officially devised by the Ministry of Environment (2010), yet remains poorly implemented. At the international level, P. pselaphon is listed on the Appendix II of CITES, and the Ogasawara Islands, to which this species is endemic, have been a UNESCO Natural World Heritage since 2011.

The remote islands of Kita-Iwo-jima and Minami-Iwo-jima are protected and uninhabited. Iwo-jima hosts a military base and is not accessible to civilians, which significantly hinders research and conservation.

There is an alarming lack of rigorous scientific research on P. pselaphon to support conservation policies. Moreover, monitoring of the subpopulations, which is of paramount importance, is not carried out in a regular and transparent manner and results are not disclosed publicly. Furthermore, conservation efforts on other islands than Chichi-jima (especially on Haha-jima) remain inexistent.

Citation: Vincenot, C. 2017. Pteropus pselaphon. The IUCN Red List of Threatened Species 2017: e.T18752A22085351. . Downloaded on 23 September 2017.
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