We analyzed the ultrasonic calls of adult black rats,
Rattus rattus, with acoustic analysis software, Adobe Audition 2.0. The rats intermittently produced 1 to 7 ultrasound waves in a series of calls. The waves showed a higher frequency and longer duration at the start of the calls than in the subsequent waves. The mean frequencies of the calls at the start, 28.9±3.0 kHz, were significantly higher than at the end, 27.5±2.3 kHz (
p<0.0001). The mean frequencies in females, 28.5±1.5 kHz, were significantly higher than in males, 26.3±1.4 kHz (
p<0.0001). The mean duration of the ultrasound calls in females, 920±612 ms, was longer than in males, 700±416 ms. There was a significant difference between males and females in the duration of the calls (
p<0.01).
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