In Eonycteris and five other genera of fruit bats in the subfamily Macroglossinae, the tongue is long, slender, and protrusible, with brushlike projections for picking up nectar and pollen, and the snout is long and slender. The cheek teeth are small, barely showing above the gums. The macroglossine type of tongue, in combination with the length of the tail, is characteristic of Eonycteris. The absence of a claw on the index finger is also an aid in distinguishing Eonycteris. E. robusta has a kidney-shaped gland on either side of the anus in both sexes.
Dawn bats occur in a variety of habitats, including forests and cultivated areas.
E. spelaea has been noted darting in and out among agave flowers, which are remarkable for their long and projecting stamens. The bats alighted occasionally for a few minutes. The stomach of one of these bats contained only pollen. These bats are gregarious. Several hundred individuals of E. robusta were found clinging to the ceiling of a cave in Luzon.