Data accompanying: Experimental winter warming increases activity with signs of potential DNA damage in common wall lizards (accepted in Journal of Experimental Biology, 2025, doi:10.1242/jeb.251440) This work was supported by the Natural Environment Research Council (NERC) Envision Doctoral Training Programme (project number: 2737291) and an Amphibian and Reptile Conservation Trust grant awarded to M.R. Open Access funding provided by Bangor University. Deposited in PMC for immediate release. Any queries or questions, please direct them to miaryras [at] gmail.com or k.macleod [at] bangor.ac.uk. Content: Datafiles – data used for analysis of activity levels, body condition, and oxidative status indices of common wall lizard. See paper and associated supplementary material for more details (doi:10.1242/jeb.251440). Metadata notes: experimental_year: year1 or year2 period: hibernation or recovery treatment: cold (overwintering temperature maintained at 4±1°C), mild (8±1°C), fluctuation (alternation between 5 days of 4±1°C and 2 days of 8±1°C) phase_fluctuationtrt refers to the two phases of the fluctuation treatment with cool being 4±1°C and warm being 8±1°C in the alertness_&_location_change dataset, 0 refers to absence and 1 refers to presence in the activity_video dataset: total_nb refers to the total number of lizards inside a terrarium, under_shelter_nb indicates the number of lizards under shelters, out_shelter_nb indicates the number of lizards outside shelters and prox_water_nb indicates the number of lizards within 1cm of the water source hibernation_history: first_time indicates first-time hibernators during the experiment and second_time refers to repeated individuals from previous year time_point: the 3 variables refer to the start of hibernation (start), the end of hibernation (emergence) and the end of the recovery period (recovery) SVL: Snout-Vent Length residuals refer to the residuals of the linear regression of log10-transformed body mass on log10-transformed SVL, calculated separately by sex (also the metric for body condition index) in the oxidative_status_&_BCI dataset: BCI_hibernation refers to the body condition index at the end of the overwintering experiment and BCI_recovery refers to the body condition index at the end of the recovery period TAC: Total Antioxidant Capacity MDA: Malondialdehyde 8-OHdG: 8-hydroxy-2’-deoxyguanosine 8-hydroxyguanosine, and 8-hydroxyguanine