What are they good for?: Ultrasonic vocalizations as social communication signals in rats

Rats emit ultrasonic vocalizations in a variety of appetitive and aversive contexts. Although the reason why these calls are emitted is yet unknown, two prominent theories exist, the affective state theory and the social communication theory. This thesis will provide evidence to support the theory that these calls are emitted as a form of social communication. Four experiments will be presented, each testing a facet of the social communication theory. These experiments provide evidence that the calls are linked to social stimuli over non-social reward, and are emitted in divergent patterns depending on strain, regardless of depressive state. Further, they demonstrate that not all appetitive rewards elicit the same calling response, and that the calls emitted have a direct impact on conspecific behaviour. Overall, it is concluded that, although some vocalizations may be an indicator of the rat’s affective state, they are also used as a form of social communication.