Mammals are poor colonisers of oceanic islands and the further or more islolated the island from the mainland source, the greater decline in size and/or diversity. The one exception is the order Chiroptera, and both megachiropterans (fruit bats) and microchiropterans (insectivorous bats) populated the Mascarenes. Members of the large fruit bat genus Pteropus are particularly adept colonisers of remote islands and three species once occurred on the Mascarenes, each species is derived from a different subgenus (Novak, 1991). Insectivorous bats are also common on the Mascarenes but exhibit little diversity.

Fruit bats (Megachiroptera)

Flying foxes (Pteropus sp.) were first reported in 1598 and mentioned again throughout the occupation of Mauritius and Réunion. Three species are known to have inhabited Mauritius and Réunion but most observers only mention one. Pteropus niger, the greater flying fox and P. subniger, the lesser flying fox were sympatric on Mauritius and Réunion but both had different roosting habits. The third Mascarene species, Pteropus rodricensis, originally thought to be endemic to Rodrigues, is now known to have occurred also on Mauritius. Flying foxes are everywhere considered a delicacy and are caught indiscriminately. This has resulted in a number of extinctions, particularly in the South Pacific, and oceanic island species are everywhere threatened. The lesser flying fox roosted in tree cavities and amongst rocks and would have been particularly susceptible to hunting. The lesser flying fox survived on Mauritius until 1864 and on Réunion until c.1860 but is now extinct. The greater flying fox is endangered and survives in small numbers on Mauritius but became extinct on Réunion c.1800. P. rodricensis was reduced to perilously low numbers in the 1970s, but the population has now recovered to the thousands.

Insectivorous bats (Microchiroptera)

Two species of small bat, Taphozous mauritianus and Tadarida acetabulosus, which are comparatively common at present and widespread on Mauritius and Réunion, do not differ morphologically from the same species on the African Mainland and Madagascar. A DNA analysis would be useful to confirm their affinities. A third species Scotophilus borbonicus, which may have been endemic to Réunion, has not been seen since 1867 and is presumed extinct.

Manatees and Dugongs (Sirenia)

Dugongs, Dugong dugong, were once native to the Mascarenes, breeding within the lagoons on Mauritius and Rodrigues. They were considered a valuable food item and were indiscriminately hunted. Their decline was rapid and they become extremely rare by the 1730s on Mauritius, although the last specimens may have survived until the turn of the century. On Rodrigues, Leguat described the suckling behaviour of nursing dugongs and vast numbers were found within the lagoon; Tafforet in 1726 noted them as being common, but Pingré in 1761 listed them as rare. This was the last account and dugongs are now extirpated in the Mascarenes.