Affect Of Population Size On Ultrasonic Vocalisations Of Wild-Type House Mice

House mice (Mus musculus) like other rodents emit ultrasonic vocalisations (USVs) as a form of communication; their call types are diverse and form a vital role in their everyday lives. In January 2019 wild strain mice housed within a mixed pen environment showed an observed shift in the length, frequency and type of USVs emitted after a population cull. This paper presents data to provide an explanation for the observed change in behaviour and motivators behind USV production. The shift in USVs was observed across all mice demographics with little influence from social experiences, external temperature fluctuations
or psychological implications from the cull. The population size caused an initial significant difference (p=0.000000000000004) in number of USVs emitted, with less than 35% of the original number of USVs produced after the population cull. Subsequent interactions between the number of USVs and population size revealed that it was not the population size but the impact of the population dynamics on the colony’s genetic diversity causing the shift in USVs. The type of calls emitted also significantly changed, with the production of complex calls occurring after the first genetic bottleneck. The progression of complex call types thereafter revealed insights into the development of USVs and the effect of genetics on USV evolution.