Isolation-induced ultrasonic vocalizations in pups: A comparison between Long-Evans, Sprague-Dawley, and Wistar rats.

Rat pup ultrasonic vocalizations (USV) are usually studied in outbred rats belonging to either Long-Evans, Sprague-Dawley, or Wistar stocks, but these were not compared so far. We therefore performed a stock comparison and analyzed USV of male pups (postnatal day 11) belonging to these three stocks. Pups of all three stocks showed substantial isolation-induced USV, but differed in various call features, like call numbers, peak frequency, and frequency modulation. Also, three different call types were identified by means of a quantitative approach based on peak frequency and frequency modulation, and it was found that their proportions differed between stocks. These results are discussed with respect to functional aspects of pup USV.