[This dataset is embargoed until November 20, 2025]. This dataset contains biologging data of captive red deer Cervus elaphus, to study sleep behaviour. This includes acceleration (m/s2), magnetometer (gauss), and temperature (degrees Celsius) measurements, collected using collar-mounted accelerometer and magnetometer recorders at 20Hz. This data was collected from 18 adult individuals; 13 male, 5 female, in 2023 over three deployments. Deployment 1 (males) 13/06/23 – 1/8/23; deployment 2 (males) 04/09/23 – 08/11/23; deployment 3 (females) 13/11/23 – 21/11/23. Deer were housed at the VUZV facility, Uhrineves, Prague, Czech Republic. This dataset was funded by NERC, as part of project “NE/X010368/1: Sleep in the landscape of fear” and was measured to aid in the creation of a classification model to detect sleep in red deer from collar accelerometers, as well as to test arousal thresholds in sleeping deer.