Female C57BL/6J mice perform distinctive urination behaviour accompanied by ultrasonic vocalisations sequences with a stereotypic temporal organisation

Ultrasonic vocalisations (USVs) are largely studied in mice as a marker of social communication. These USVs are usually recorded during short social encounters in unfamiliar test cages. In the present study, we explored how freely interacting pairs of C57BL/6J adult female mice spontaneously use USVs over long-term monitoring. In this situation, we discovered that these mice display a previously undescribed behaviour: they emit specific USV sequences while depositing a large quantity of urine in a corner of the cage. The most striking feature of USVs accompanying this vocalised urination behaviour was the stereotyped duration of the inter-USV intervals. The variability in the frequency of occurrence of this behaviour was important between pairs. Interestingly, when accompanied by the specific USV sequence, urination was correlated with a significant increase in locomotor activity in both the emitter and the cage mate, in contrast with urination without USVs. Altogether, the observation and description of this vocalised urination behaviour argue for exploring mouse vocalisations at the sequence level to understand the USV-behaviours interactions.