The Bonin flying fox: an endangered Japanese rarity



by LORENZO CIOTTI

The Bonin flying fox: an endangered Japanese rarity

The Bonin flying fox is a bat endemic to the Ogasawara Islands, Japan. The range of this species is restricted to the Ogasawara Islands: Chichi Jima, Haha Jima, Kita Iwo Jima, Iwo Jima and Minami Iwo Jima. Lives in native forests.

The IUCN Red List, considering the narrowness of its range and its fragmentation, the slow decline of its habitat, classifies P. pselaphon as a critically endangered species. They are considered endangered because their extent of occurrence is less than 100 km2, their habitat is severely fragmented, and the population is estimated at fewer than 250 mature individuals.

In 1969, this species was listed as a Natural Monument of Japan. The fur is long, dense, semi-erect over the shoulders and extends over the lower limbs to the toes. The general body color is blackish-brown, more or less strewn with long, coarse hairs tipped greyish-white.

The head has dark brown reflections, the muzzle is long, the nostrils are slightly tubular and separated by a deep longitudinal furrow which extends to the upper lip, the eyes are large.

The Bonin flying fox: an endangered Japanese rarity

The ears are short, triangular, partially hidden in the fur and with a concave rear edge just below the tip.

The wing membranes are attached along the sides and posteriorly to the tip of the second metatarsal. It has no tail, while the uropatagium, densely covered with hair, is reduced to a thin membrane along the inner parts of the lower limbs.

It is a medium-sized bat, with forearm length between 124.9 and 142.4 mm, foot length between 42 and 50 mm, and ear length between 23 and 29 mm. It takes refuge in the dense foliage of trees in small groups during the winter and singly in the summer.

Its robust dentition indicates a diet of tough-skinned fruits, including some Manilkara species, and Agave americana flowers. Since the fruit is usually harvested on plantations, it is considered harmful to crops. The population of bats Chichijima Island was estimated at 150 individuals in 1997, but by 2002, it was estimated at only 65-80 individuals.

Possible reasons for their decline include entanglement in agricultural nets and depredation by feral cats. It is speculated that they are threatened by competition with invasive species, including rats, white-eyes, and honey bees.