Land animals
Because the Ogasawara Islands are oceanic islands that have never been connected to a continental landmass, they are home to a uniquely speciated population of organisms with high endemism. The terrestrial animals that inhabit the Ogasawara Islands can be said to be the result of unlikely happenstance, whereby ancestors were somehow able to cross the ocean. Of the naturally distributed terrestrial animals, with the exception of birds, which are relatively mobile, the only mammal species present is the endemic Bonin flying fox (Pteropus pselaphon). There are only two species of reptiles, the Ogasawara snake-eyed skink (Cryptoblepharus nigropunctatus) and the Micronesian saw-tailed gecko (Perochirus ateles), and no amphibians. Birds are considered relatively mobile because of their ability to fly, but the Ogasawara Islands, 1,000 km distant from Honshu, are not an easy place to reach. On the other hand, the birds that were able to reach the islands evolved uniquely and have become established as endemic species or endemic subspecies. Four endemic species of terrestrial birds are believed to have once been on the islands, but today the Bonin honeyeater is the only existing endemic land bird. (Ref. 1, 2) 

The Ogasawara Islands are designated as Important Bird Area (IBA) by BirdLife International. In addition, the Ogasawara Island Group is designated as an Endemic Bird Area (EBA) by BirdLife International, because they are the habitat of the endemic Bonin honeyeater and Red-headed wood pigeon (Columba janthina nitens), a restricted-range species. (Ref.1,2)

Marine animals 
Approximately 1,000 species of fish, 23 species of cetaceans, 1,100 species of gastropods, and 220 species of reef-building corals have been reported in the coastal areas of the Ogasawara Islands. Of these, fishes share more in common with southern regions such as the Mariana Islands than with northern regions such as the Izu Islands. About 30% of the world’s marine cetacean species can be found in the waters around the Ogasawara Islands, apart from four species that spend their lives in freshwater. (Ref. 1, 2)
 

Ref. 1: Government of Japan, Nomination of the Ogasawara Islands for Inscription on the World Heritage List, 2010, pp.53-57, pp.65-66

Ref. 2: Tokyo Metropolitan Ogasawara Branch Office, Kannai Gaiyo (Overview of the Jurisdiction), 2019 ed., pp.41-42.