Pollination in the baobab is achieved primarily by fruit bats, in West Africa mainly "Eidolon helvum", "Epomorphorus gambianus" and "Rousettus aegyptiacus". The flowers are also visited by bush babies, galagos, and several kinds of insect that may also assist. Some aspects of the baobab's reproductive biology are not yet understood. It is still speculated whether fertile baobab seeds can result from pollination by the tree's own pollen. It would appear as if pollen from another tree is required for fertile seed, as isolated trees do form seed, only to abort them at a late stage. The existence of some very isolated trees, may then be due to their self-incompatibility and inability to reproduce.