the literature primarily examines the relationship between ultrasonic vocalizations and rodent behaviour. the 40-khz call of a pup is an important to its survival. if pups are left behind and they emit a 40-khz call, this will induce retrieval behaviour in the mother. when one pup is separated from their littermates, they will produce ultrasonic vocalizations at high rates. compounds including benzodiazepines, which are positive modulators of gaba receptors, will decrease the production of ultrasonic vocalizations which are emitted in response to social isolation. during emission of 22-khz calls, juveniles and adults are often exhibiting freezing behaviour and experiencing an increase in heart rate and blood pressure. since 22-khz calls are emitted in response to unpleasant situations and noxious stimuli, it has been thought that these calls serve two functions: reflecting anxiety, and communication. with respect to communication, these calls could be emitted as threat signalling to conspecifics or individuals of other species to decrease the probability of an aggressive encounter, or they could be emitted as alarm calling to warn other individuals in the population of imminent danger. 50-khz calls may promote social interaction among conspecifics by inducing and maintaining them. they are thought to be indicative of positive affective states. these 50-khz calls are also emitted in anticipation of a rewarding stimulus.