Ultrasound and aggressive behaviour in rats and other small mammals

Abstract

Aggressive behaviour has been observed in rats, Rattus norvegicus, and fourteen other species of small mammals. Ultrasounds were detected during aggressive behaviour in at least seven of these species, and in rats two distinct types of signal were recorded. Short ultrasounds of 3 to 65 ms duration and at frequencies of about 50 kHz were produced in aggressive situations, while long pulses up to 3400 ms duration and at about 25 kHz appeared to be synchronous with the long exhalations of submissive rats. Aggressive behaviour was reduced in encounters where long pulses were emitted. The physical characteristics of the ultrasounds produced by the different species are described and the importance of these signals in the establishment and maintenance of social relationships in small mammals is discussed.