[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. Full details about this dataset can be found at https://doi.org/10.5285/e7fdf789-e663-4422-92c2-ea8019b3cc26