Effective Survey Methods for the Elusive Data Deficient Black Flying Squirrel (Aeromys tephromelas) in Sabah, Malaysia Facilitate First Vocalisation Record

Flying squirrels are nocturnal, gliding relatives of tree and ground squirrels (order Sciuridae). Despite 49 species existing, literature on Asiatic flying squirrels is scarce, thus they are overlooked in conservation action plans. Recently, three species of giant flying squirrel (<i>Aeromys tephromelas</i>, <i>Petaurista petaurista</i> and <i>Aeromys thomasi</i>) were observed during a nocturnal mammal survey at the Rainforest Discovery Centre (RDC), an Eco centre at the edge of the Kabili-Sepilok forest reserve in Sepilok, Sabah (Malaysia, Borneo). The survey (February-March 2023) incorporated the use of red LED spotlighting, thermal imaging and bioacoustic recording during systematic along-line point counts. This is the first report on flying squirrel ecology in Sabah and the first focused publication on the 'giant' black flying squirrel (<i>A. tephromelas</i>), categorised by the IUCN as Data Deficient. The most notable result was the first documentation of a black flying squirrel vocalisation event (106 calls at a frequency range of 0.75-2.69 kHz and mean duration of 1.4 s). Although call function was not determined, this result sheds light on a previously unknown part of their ecology. These results stress the urgency for further research on the black flying squirrel to evaluate their current extinction risk, considering deforestation is prevalent across most of their distribution.