The current study provides details of sleep (or inactivity) in two wild, free-roaming African
elephant matriarchs studied in their natural habitat with remote monitoring using an acti-
watch subcutaneously implanted in the trunk, a standard elephant collar equipped with a
GPS system and gyroscope, and a portable weather station. We found that these two ele-
phants were polyphasic sleepers, had an average daily total sleep time of 2 h, mostly
between 02:00 and 06:00, and displayed the shortest daily sleep time of any mammal
recorded to date. Moreover, these two elephants exhibited both standing and recumbent
sleep, but only exhibited recumbent sleep every third or fourth day, potentially limiting their
ability to enter REM sleep on a daily basis. In addition, we observed on five occasions that
the elephants went without sleep for up to 46 h and traversed around 30 km in 10 h, possibly
due to disturbances such as potential predation or poaching events, or a bull elephant in
musth. They exhibited no form of sleep rebound following a night without sleep. Environ-
mental conditions, especially ambient air temperature and relative humidity, analysed as
wet-bulb globe temperature, reliably predict sleep onset and offset times. The elephants
selected novel sleep sites each night and the amount of activity between sleep periods did
not affect the amount of sleep. A number of similarities and differences to studies of ele-
phant sleep in captivity are noted, and specific factors shaping sleep architecture in ele-
phants, on various temporal scales, are discussed.