Figure 1. Extracting activity and sleep from accelerometry in a group of wild olive baboons.

Adapting algorithms developed by van Hees et al., 2015 and van Hees et al., 2018, we used the vectorial dynamic body acceleration (VeDBA), a measure of overall activity, to determine the sleep onset and awakening times (A; orange dashed lines), as well as periods of wake after sleep onset (A; blue shading) for each individual baboon on each day. These metrics allowed us to calculate the total sleep time, sleep period duration, sleep efficiency, and sleep fragmentation. The plot (A) shows the data of one individual within a single noon-to-noon period as an example. Averaged across all individuals on all nights (N = 354 baboon-nights), the log VeDBA shows that baboons exhibit activity patterns typical of a diurnal animal with monophasic sleep (B), with a consolidated period of very low levels of activity during the night. Although the timing of waking (C; dotted line) was more consistent across the group and across the study period than the timing of sleep onset (C; dashed line), both sleep onset and waking typically occurred within astronomical twilight. The red shading in (B) indicates ±1 SE. In all subplots, the gray shaded region depicts the period between sunset and sunrise, with double shading from the end of evening astronomical twilight to the beginning of morning astronomical twilight.