Pete Oxford / Greater Sac-winged Bat (Saccopteryx bilineata) trio roosting, Yasuni National Park, Amazon Rainforest, Ecuador

Claudio Contreras / Gray Sac-winged Bat (Balantiopteryx plicata). Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, June.

Claudio Contreras / Gray Sac-winged Bat (Balantiopteryx plicata) clinging to rock. Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, September.

Christian Ziegler / Greater Sac-winged Bat (Saccopteryx bilineata) detail of sac on wing which is used to attract females and mark territory, Smithsonian Tropical Research Station, Barro Colorado Island, Panama

Christian Ziegler / Greater Sac-winged Bat (Saccopteryx bilineata) detail of sac on wing which is used to attract females and mark territory, Smithsonian Tropical Research Station, Barro Colorado Island, Panama

Solvin Zankl / Greater white lined / Sac-winged Bat (Saccopteryx bilineata) La Selva Biological Station, Costa Rica

Murray Cooper / Greater Sac-winged Bat (Saccopteryx bilineata) group roosting on tree, Amazon, Ecuador

Claudio Contreras / Lesser doglike sac-winged bat (Peropteryx macrotis) roosting, Uxmal, Yucatan Peninsula, Mexico, January

James Christensen / Chestnut Sac-winged Bat (Cormura brevirostris) roosting in limestone cave, Colon, Panama