We monitored the individual and social behaviours of each quartet of mice over three days and nights in the Live Mouse Tracker system (LMT, plugin 931; de Chaumont et al. 2019 Nat. Biomed. Engin.). This system tracks individually mice living in a group over several days and nights and extracts automatically the number, total duration and mean duration of more than thirty behavioural events describing the posture of the mouse, the types of social contacts, the dynamic social approach and escapes and complex social groupings (see de Chaumont et al. 2019 Nat. Biomed. Engin.). In this system, the four mice (10-14 weeks of age; 2 WT mice and 2 Del/+ mice) from the same housing cage (housed together from weaning on) were left undisturbed for 71 hours in a large transparent Plexiglas cage (50 x 50 x 40 cm), with fresh bedding, a house (width: 100 mm, depth: 75 mm, height: 40 mm) in red Plexiglas, 6 dental cotton rolls as well as food and water ad libitum. Light/dark cycle and temperature conditions were similar to those of the housing room (12/12h light/dark, lights on at 07:00 AM, 100 lux when the lights were on). Each recording session started between 03:00 and 04:00 PM. At the end of the session, mice were placed back in their home cage and the LMT setup was cleaned with soap water and dried with paper towels. The upload includes the sqlite database from LMT (processed).