long_chase_2021-04-22_23-28-26_0013362

C57BL/6 J female mice were purchased from Charles River Laboratories (L’Arbresle, France) at 6 weeks of age. Upon arrival, mice were housed in pairs that were conserved throughout the experiment. After one week of acclimation, we identified each individual with a subcutaneous Radio Frequency Identification (RFID) tag (APT12 PIT tags; Biomark, Inc., Boise, The United States of America) inserted under gas anaesthesia (Isoflurane) with local analgesia (Lidor 20 mg/ml, with 40μl/10g mouse). RFID tags were positioned in the lower part of the left flank. Mice were allowed to recover for at least one week. We continuously recorded dyadic interactions between two familiar female mice of the same age (8–12 weeks of age). Recordings started between 03:00 and 04:00 PM and lasted undisturbed 47h long, that is, two days and nights minus 1h for cleaning in between two recording sessions. We coupled the Live Mouse Tracker (LMT) system (https://micecraft. org/lmt; version 931; [6]) with the Avisoft Ultrasound Gate 416 (300kHz sampling rate, 16-bit format; trigger: level of this channel; pre-trigger: 1s; hold time: 1s; duration: >0.005s; trigger event: 2% energy in 25–125kHz with entropy <50%; Avisoft Bioacoustics, Glienecke, Germany) connected to a CM16/CMPA microphone (Avisoft Bioacoustics, Glienecke, Germany). LMT and Avisoft systems were synchronised. The USV sequence was recorded during long chase between the two animals.