| A plastic bank-issued credit card weighs about 5 grams. Spix’s Disk-winged Bat weighs about 3 to 5 grams. This is a very tiny mammal. Its size is not unusual, however. There are many very tiny bats. This bat’s claim to fame is that it has suction cups on its feet and at the base of its thumbs. Three species of New World bats, this one and two others in the genus Thyroptera, have this adaptation. There is also one species of sucker-footed bat in Madagascar that has similar but less well-developed suction pads.
Spix's Disk-winged Bats find new, smooth leaves that hang like vertical tubes in which to roost, and line themselves up one behind another, roosting upright inside the leaf instead of hanging head-down. With their suction-cup disks, they can hold on or crawl rapidly along its slippery surface. In a day or so, the leaf unfurls and the bats find another. They are agile and maneuver well in flight, and probably eat small insects they catch while airborne.
Head and Body: 37-46 mm; Tail: 24-33 mm
Spix, J.B. von, 1823. Simiarum et Vespertilionum Brasiliensium Species Novae, ou histoire naturalle des espèces nouvells de singes et de chauves-souris observées et recuillies pendant le voyage dans l’intériur du Brésil execute par order de S.M.
Mammal Species of the World
Mammalian Species, American Society of Mammalogists' species account