Distribution of arboreal nocturnal mammals in northern Borneo

This study aimed to determine the distribution of arboreal nocturnal mammals in northern Borneo, in particular the Bornean Striped Palm Civet Arctogalidia stigmatica, Philippine Slow Loris Nycticebus menagensis, Western Tarsier Cephalophacus bancanus, Bornean Colugo Galeopterus borneanus and Island Palm Civet Paradoxurus philippinensis. Nocturnal mammals were surveyed at six sites in northern Borneo of varying habitat types and patterns of disturbance. Standardised point and line transects following predetermined paths were used and mammals searched for with the aid of a thermal imaging camera, a red-filtered head lamp and alternatively, a white light head lamp. With 49% of the observations, A. stigmatica (36 individuals/6 sites) was the most common species across the study sites, followed in abundance by N. menagensis (16/5), C. bancanus (14/3), G. borneanus (11/3) and P. philippinensis (2/2). The highest arboreal mammal density of 4.4 individuals/km was found at our Kiudang study site in Tutong District. In addition to the five focal arboreal mammals, 20 additional species were observed throughout the study. This study reveals variation in arboreal nocturnal mammal presence with habitat type that is likely influenced by diet preferences, habitat fragmentation, and the level of hunting pressure. Further surveys combined with arboreal camera trapping will be necessary to study the secretive and easily disturbed arboreal nocturnal mammals of Borneo.

Diurnal motor activity and “sunbathing” behaviour in crested porcupine (Hystrix cristata L., 1758)

The crested porcupine is a mainly nocturnal mammal that shows both moonlight avoidance and some diurnal motor activity, the latter as an extension of its night-time foraging behaviour. Furthermore, a peculiar daytime behaviour, described as “sunbathing”, was reported as episodic in H. africaeaustralis. Between 2016 and 2019 a camera-trapping monitoring was performed within 10 porcupine settlements in order to detect the diurnal motor activity and to verify and describe the sunbathing behaviour in crested porcupine. Out of 1,003 trap days, a total of 148 events of diurnal motor activity were recorded. The diurnal motor activity occurred throughout the year mainly between December and June from 15:00 to 16:00, with no statistical difference between cubs, youngsters and adults. The sunbathing behaviour was detected for a total of 36 episodes recorded. Sunbathing was performed mainly by cubs. The sunbathing behaviour occurred only between April and June during the hottest hours of the day (11:00 to 12:00). Diurnal motor activity and sunbathing behaviour of porcupine are discussed in relation to food availability and porcupine physiology.

Bat echolocation calls facilitate social communication

Bat echolocation is primarily used for orientation and foraging but also holds great potential for social communication. The communicative function of echolocation calls is still largely unstudied, especially in the wild. Eavesdropping on vocal signatures encoding social information in echolocation calls has not, to our knowledge, been studied in free-living bats so far. We analysed echolocation calls of the polygynous bat Saccopteryx bilineata and found pronounced vocal signatures encoding sex and individual identity. We showed experimentally that free-living males discriminate approaching male and female conspecifics solely based on their echolocation calls. Males always produced aggressive vocalizations when hearing male echolocation calls and courtship vocalizations when hearing female echolocation calls; hence, they responded with complex social vocalizations in the appropriate social context. Our study demonstrates that social information encoded in bat echolocation calls plays a crucial and hitherto underestimated role for eavesdropping conspecifics and thus facilitates social communication in a highly mobile nocturnal mammal.