| Abstrak/Abstract |
Among primates, the suborder Haplorhini is considered to have evolved a consolidated monophasic
sleep pattern, with diurnal species requiring a shorter sleep duration than nocturnal species. Only a
few primate species have been systematically studied in their natural habitat where environmental
variables, including temperature and light, have a major infuence on sleep and activity patterns. Here
we report the frst sleep study on a nocturnal primate performed in the wild. We ftted seven wild Javan
slow lorises (Nycticebus javanicus) in West Java, Indonesia with accelerometers that collected activity
data, and installed climate loggers in each individual’s home range to collect ambient temperature
readings (over 321 days in total). All individuals showed a strictly nocturnal pattern of activity and
displayed a striking synchronisation of onset and cessation of activity in relation to sunset and sunrise.
The longest consolidated rest episodes were typically clustered near the beginning and towards the
end of the light period, and this pattern was inversely related to daily fuctuations of the ambient
temperature. The striking relationship between daily activity patterns, light levels and temperature
suggests a major role of the environment in shaping the daily architecture of waking and sleep. We
concluded that well-known phenotypic variability in daily sleep amount and architecture across species
may represent an adaptation to changes in the environment. Our data suggest that the consolidated
monophasic sleep patterns shaped by environmental pressures observed in slow lorises represent
phylogenetic inertia in the evolution of sleep patterns in humans. |
