The aim of the research was to verify whether vocalizations at the frequency of 22 kHz can be an effective indicator of emotional arousal of rats in behavioral tests. The research was conducted with the use of 48 Sprague-Dawley strain rats. The rats were divided into two groups: of high or low reactivity, through preselection in the open field test. The rats were exposed to a stressor (a nip on the neck) and their vocalizations were recorded with the use of an ultrasound detector. Presented results suggest that vocalization of warning calls can be considered as an indicator of emotional reactivity in rats.