Members of Pteropodidae are known colloquially as the flying foxes, or Old World fruit bats. The family is composed of 41 genera and about 170 species. The most species-rich genus in the family is Pteropus with 59 species, many of which are island endemics. Body and wing size ranges from small (37 mm forearm length) to large (220 mm forearm length). The family boasts the largest bats in the world. Pteropus vampyrus individuals have a wingspan of up to 1.7 m. Pteropus giganteus individuals have a comparable wingspan but a greater mass, with males weighing between 1.3 and 1.6 kg. Pteropodids are strictly vegetarian, foraging for fruits, nectar, and pollen using their sight and a sensitive olfactory system. Bats of the genus Rousettus use tongue clicks as a crude form of echolocation while navigating in the dark. Some species are migratory, covering vast distances, while others have more moderate home ranges. Eidolon helvum individuals aggregate in numbers reaching the hundreds of thousands, yet many species roost with only a few conspecifics. Members of Pteropodidae service the ecosystems they inhabit by playing important roles as pollinators and seed dispersers.